TY - THES A1 - Toksabay, Sinem T1 - Synthesis and on surface self assembly properties of pi extended tribenzotriquinacenes T1 - Synthese und selbstorganisierende Eigenschaften von pi-erweitertem Tribenzotriquinacenen an der Oberfläche N2 - Tribenzotriquinacene (TBTQ) is a polycyclic aromatic framework with a particularly rigid, C3v symmetrical, bowl-shaped core bearing three mutually fused indane wings. It has been discussed as a defect center for a nanographene by Kuck and colleagues. Therefore, extended TBTQ structures are promising models for saturated defect structures in graphene and graphene like molecules and could be used to investigate the role of defects for the electronic properties of graphene. With this motivation, three different pi-extended TBTQ derivatives have been synthesized in this work. Several different Scholl reaction conditions were tried to obtain fully annulated product of hexaphenyl substituted TBTQ. The desired benzannulated TBTQ derivative could not be obtained due to unfavourable electron density in the respective positions of the molecule and increased reactivity of the bay position of the precursor. As an another method for benzannulation is the on-surface synthesis of graphene flakes and can be carried out using electron beams e.g. in a tunneling microscope (STM). According to our previous research, the parent system TBTQ and centro-methyl TBTQ on silver and gold surfaces showed that the gas phase deposition of these molecules gives rise to the formation of highly ordered two-dimensional assemblies with unique structural features. This shows the feasibility for the formation of defective graphene networks starting from the parent structures. Therefore, the same deposition technique was used to deposit Me-TBTQ(OAc)3Ph6, and investigate the molecular self-assembly properties directly on the surface of Cu (111). In summary, the substrate temperature dependent self-assembly of Me-TBTQ(OAc)3Ph6 molecules on Cu(111), shows the following evolution of orientations. At room temperature, molecules form dimers, which construct a higher-coverage honeycomb lattice. Furthermore, one of the acetyl group located in the bay positions of the TBTQ core is cleaved and the remaining two induce the metal-molecule interaction. It was presumed that by increasing the temperature to 393 K, the remaining acetyl and methyl groups would beeliminated from the molecular structure.In addition, the smaller TBTQ-Ph6 molecules preferably lie flat on Cu(111) crystal and allowing the molecules to settle into a C3-symmetry and form a dense hexagonal structure. N2 - Tribenzotriquinacen (TBTQ) ist eine polyzyklische aromatische Verbindung mit einem besonders starren, C3v-symmetrischen, schalenförmigen Kern, der drei anellierte Indan-Flügel trägt. Es wurde von Kuck und Kollegen als Defektzentrum für Nanographen untersucht. Daher sind erweiterte TBTQ-Strukturen vielversprechende Modelle für gesättigte Defektstrukturen in Graphen und graphenähnlichen Molekülen, die dazu verwendet werden können, um die Rolle Defekten auf die Ausprägung der elektronischen Eigenschaften von Graphen zu untersuchen. Mit dieser Motivation wurden in dieser Arbeit drei verschiedene TBTQ-Derivate mit erweitertem -System synthetisiert. Um im Anschluss eine vollständige Annellierung und damit Konjugation des p-Systems zu erreichen, wurden verschiedene Scholl-Reaktionen getestet, um das dreifach anellierte Produkt aus hexaphenylsubstituiertem TBTQ zu erhalten. Das gewünschte benzannulierte TBTQ-Derivat konnte aufgrund der relativ geringen Elektronendichte an den Annellierungspositionen und der erhöhten Reaktivität der Bay-Positionen des Moleküls nicht erhalten werden. Eine weitere Möglichkeit zur Annellierung von Nanographenen besteht in der On-Surface-Synthese. Diese kann mit Elektronenstrahlen z.B. in einem Rastertunnelmikroskop (STM) durchgeführt werden. Nach unseren früheren Untersuchungen, hochauflösende STM-Experimente mit dem Stammsystem TBTQ und centro-methyl TBTQ auf Silber- und Goldoberflächen, dass die Gasphasenabscheidung dieser Moleküle zur Bildung hochgeordneter zweidimensionaler Assemblierte mit einzigartigen strukturellen Eigenschaften führt. Dies zeigt die Möglichkeit zur Bildung von defekthaltigen Graphen-Netzwerken ausgehend von den Stammsystemen. Daher wurde hier die gleiche Abscheidungstechnik verwendet, um für Me-TBTQ(OAc)3Ph6 die molekulare Selbstanordnung auf der Oberfläche von Cu(111) untersuchen. Zusammenfassend zeigt die Selbstorganisation von Me-TBTQ(OAc)3Ph6 auf Cu(111) eine ausgeprägte Temperaturabhängigkeit. Die Moleküle bilden bei 363 K ein höheres Wabengitter aus. Außerdem wird eine der Acetylgruppen, die sich in den Bay-Positionen des TBTQ-Kerns befinden, abgespalten und die verbleibenden Gruppen wechselwirken mit der Metalloberfläche. Daher stehen sich die Molekülschalen als einander zugewandte Halbkugeln gegenüber. Es wird vermutet, dass durch die Erhöhung der Temperatur auf 393 K die verbleibenden Acetyl- und Methylgruppen aus der Molekülstruktur eliminiert werden. Außerdem liegen die kleineren TBTQ-Ph6-Moleküle bevorzugt flach auf dem Cu (111) -Kristall, so dass sich die Moleküle in der C3-Symmetrie anordnen und eine dichte hexagonale Struktur bilden KW - Triquinacenderivate KW - Aromatisch anellierte Triquinacene KW - Aromatically annulated triquinacenes KW - Chemische Synthese KW - gekrümmte Kohlenwasserstoffe KW - curved hydrocarbons KW - triquinacene derivatives KW - on surface self-assembly Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-245734 ER - TY - THES A1 - Dechant, Moritz Thomas T1 - Synthese und Struktur-Eigenschaftsbeziehungen neuer Phthalocyanin-Sternmesogene – Ein neues Design für organische, flüssigkristalline Photovoltaikmaterialien T1 - Synthesis and structure-property relationships of new phthalocyanine star mesogens - A new design for organic, liquid crystalline photovoltaic materials N2 - Es wurde eine Vielzahl neuer, flüssigkristalliner Phthalocyanin-Sternmesogene synthetisiert. Die Struktur-Eigenschaftsbeziehungen und die thermotropen Eigenschaften neuer Phthalocyanin-Sternmesogene mit Freiraum sowie von sterisch überfrachteten Verbindungen wurden insbesondere hinsichtlich der Freiraumfüllung untersucht. Diesbezüglich wurde ein neuer supramolekularer, freiraumfüllender "Klick-Prozess" zwischen einem Molekül mit Freiraum und einem sterisch überfrachteten Molekül mit vier Fullerenen beobachtet. Die photophysikalischen Eigenschaften wurden zudem insbesondere im Hinblick auf die Anwendung für die Organische Photovoltaik untersucht. N2 - A large number of new, liquid crystalline phthalocyanine star mesogens was synthesized. The structure-property relationships and the thermotropic properties of new phthalocyanine star mesogens with free space and of sterically overcrowded compounds were investigated, whereas the space-filling was of great interest. In this regard, a new supramolecular, space-filling „click-process“ between one molecule with free space and one sterically overcrowded compound with four fullerenes was observed. The photophysical properties regarding to an application for the organic photovoltaics were investigated. KW - Phthalocyanin KW - Fullerene KW - Flüssigkristalle KW - Donor-Akzeptor-Dyaden KW - Sternmesogene KW - Freiraumfüllung KW - Flüssigkristall KW - Fotovoltaik KW - Fulleren Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238888 ER - TY - THES A1 - Schindler, Dorothee T1 - Water Oxidation with Multinuclear Ruthenium Catalysts T1 - Wasseroxidation mit mehrkernigen Ruthenium-Katalysatoren N2 - In terms of the need of environmentally benign renewable and storable energy sources, splitting of water into hydrogen and oxygen by using sunlight is a promising approach. Hereby, water oxidation catalysts (WOCs) are required to perform the water oxidation comprising the transfer of four electrons to provide the reducing equivalents for producing hydrogen. The class of Ru(bda) (bda = 2,2'-bipyridine-6,6'-dicarboxylate) catalysts has proven to be efficient for this reaction. In this thesis, ligand exchange processes in Ru(bda) complexes have been analyzed and the formation of multinuclear macrocyclic WOCs was studied. Based on the knowledge acquired by these studies, new multinuclear cyclic Ru(bda) complexes have been synthesized and their catalytic efficiencies in homogeneous water oxidation have been investigated. Going one step further for setting up functional devices, molecular WOCs have been immobilized on conducting or semiconducting supporting materials. Direct anchoring on carbon nanotubes generated a promising materials for further applications. N2 - Der Klimawandel als die gesellschaftliche Herausforderung des 21. Jahrhunderts ist der Allgemeinheit in den letzten Jahren insbesondere durch Aktivitäten der jüngeren Generation mehr und mehr ins Bewusstsein gerückt. Mit ihrem Engagement in Klimabewegungen machen sie auf die Dringlichkeit aufmerksam, fossile Brennstoffe als Hauptverursacher schädlicher Emissionen zu ersetzen. Angesichts des Bedarfs an umweltfreundlichen erneuerbaren und zugleich speicherbaren Energie¬quellen ist die Erzeugung von Wasserstoff unter Verwendung von Sonnenlicht zur Spaltung von Wasser in seine Bestandteile ein vielversprechender Ansatz (Kapitel 2.1). Die Wasser¬oxidationsreaktion, die die erforderlichen Reduktionsäquivalenten für die Umwandlung von Protonen in molekularen Wasserstoff liefert, umfasst jedoch einen herausfordernden Vier-Elektronen-Transferprozess, der robuste und effiziente Katalysatoren unverzichtbar macht (Kapitel 2.2). In den letzten Jahrzehnten durchgeführte ausführliche Untersuchungen an molekularen Wasser¬oxidations¬katalysatoren (WOCs, engl: water oxidation catalysts) haben gezeigt, dass Katalysatoren, die das katalytisch aktive Ru(bda) Fragment (bda: 2,2'-bipyridin-6,6'-dicarbonsäure) enthalten, eine hohe Effizienz in der Wasseroxidation aufweisen.[41] Basierend auf diesen Erkenntnissen entwickelten Würthner und Mitarbeiter einen supra-molekularen Ansatz, bei dem drei Ru(bda) Einheiten makrozyklisch organisiert werden.[42] Diese makrozyklischen Ru(bda) Komplexe zeigten außerordentlich hohe katalytische Aktivitäten mit bedeutend höherer Umsatzfrequenz (TOF, engl: turnover frequency) und Umsatzzahl (TON, engl: turnover number) sowie einer verbesserten Stabilität des Katalysators im Vergleich zur einkernigen Referenzverbindung Ru(bda)(pic)2.[40] Interessanter¬weise wurde heraus¬gefunden, dass vermutlich ein wasserstoffverbrücktes Wasser¬netzwerk in der Kavität des Makrozyklus für schnelle Protonen-gekoppelte Elektronen-Transfer-Schritte (PCET, engl: protonen-coupled electron transfer) und somit beschleunigte Reaktionsgeschwindigkeiten verantwortlich ist. Darüber hinaus belegten mechanistische Untersuchungen einen Wechsel des katalytischen Weges von einem bimolekularen I2M (Interaktion von zwei M-O Einheiten, engl: interaction of two M-O units) Mechanismus im einkernigen Ru(bda)pic2 Referenzkomplex zu einem mononuklearen WNA (nukleophiler Wasserangriff, engl: water nucleophiilic attack) Mechanismus im dreikernigen makro-zyklischen WOC MC3 (Kapitel 2.3), was letzteren besonders interessant für anwendungs-bezogene Untersuchungen macht. ... KW - Rutheniumkomplexe KW - catalysis KW - Wasser KW - Katalyse KW - Oxidation KW - metallosupramolecular chemistry KW - ruthenium complexes KW - water oxidation KW - Ruthenium Komplexe KW - Metallosupramolekulare Chemie KW - Wasseroxidation Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-233093 ER - TY - THES A1 - Turkin, Arthur T1 - Vom Monomer zum Polymer: Iterative Synthese und optische Spektroskopie von Squarain-Oligomeren T1 - From Monomer to Polymer: Iterative Synthesis and Optical Spectroscopy of Squaraine-Oligomers N2 - Mittels einer Schutzgruppenstrategie wurden Squarain-basierte monodisperse Oligomere synthetisiert. Die lösungsmittelabhängigen Konformationen (Random Coil vs. Helix) wie auch der Faltungsprozess der Homooligomere wurden mittels optischer Spektroskopie, verschiedener NMR-Experimenten, Kleinwinkelneutronenstreuungsexperimenten sowie quantenchemischen Berechnungen näher beleuchtet. Die optisch-spektroskopischen Beobachtungen wurden mithilfe der Exzitonenkopplungstheorie und einer Orientierungs- und Winkelabhängigkeit der Übergangsdipolmomente der Oligomere erklärt. Der hohe Windungsabstand der helikalen Konformation führt zu einer Interkalation von Lösungsmittel, wodurch eine Art Klathrat gebildet wird. Zusätzlich wurden mittels eines Frenkel-Exzitonenmodells die Absorptions- und Fluoreszenzspektren modelliert. Es konnten die Exzitonendelokalisationslängen abgeschätzt und die Auswirkung der energetischen und strukturellen Unordnungen auf die Absorptions- und Fluoreszenzspektren bestimmt werden. Die Absorptionsspektren werden vorwiegend durch strukturelle Unordnungen verbreitert, die Fluoreszenzspektren dagegen von energetischen Übergangsenergieabweichungen. Weiterhin wurden auch alternierende Squarain-Cooligomere synthetisiert und mittels optischer Spektroskopie untersucht. Es wurde, abhängig von dem gewählten Lösungsmittel, eine Verschiebung der Hauptbande beobachtet, was durch einen Random Coil vs. helikale-/schlaufenartige Konformation erklärt wird. Gestützt wurde dies mittels quantenchemischen Berechnungen der jeweiligen Konformationen. Abschließend wurden alternierende Squarain-Copolymere synthetisiert, in verschiedenen Größen aufgetrennt und mittels optischer Spektroskopie untersucht. Mittels EEI2D-Experimenten wurde die Exzitonendynamik in Abhängigkeit von der Kettenlänge eingehender untersucht. Hierbei wird eine steigende, aber relativ abnehmende Kohärenzlänge bestimmt, die Auswirkungen auf die Exzitonendynamik hat. Der Exzitonentransport weist erst wellenförmiges und dann subdiffuses Verhalten auf. N2 - A protecting group strategy was employed to synthesise squaraine-based monodisperse oligomers. The solvent-dependent conformations (random coil vs. helix) as well as the folding process of the homooligomers were examined in more detail using optical spectroscopy, various NMR experiments, small-angle neutron scattering experiments, and quantum chemical calculations. The optical-spectroscopic observations were explained using exciton coupling theory and an orientation and angle dependence of the transition dipole moments of the oligomers. The high pitch of the helical conformation leads to solvent intercalation, thereby forming a type of clathrate. In addition, the absorption and fluorescence spectra were modeled using a Frenkel exciton model. The exciton delocalization lengths were estimated and the effect of the energetic and structural disorders on the absorption and fluorescence spectra were determined. The absorption spectra are mainly broadened by structural disorder, while the fluorescence spectra are broadened by energetic transition energy deviations. Alternating squaraine cooligomers were also synthesised and analysed by optical spectroscopy. Depending on the chosen solvent, a shift of the main band was observed, which is explained by a random coil vs. helical/loop-like conformation. This was supported by quantum chemical calculations of the respective conformations. Finally, alternating squaraine copolymers were synthesised, separated into different sizes and analysed by optical spectroscopy. Exciton dynamics as a function of chain length were investigated in more detail using EEI2D experiments. Here, an increasing but relatively decreasing coherence length was determined, which affects the exciton dynamics. The exciton transport shows wavelike and then sub-diffusive behaviour. KW - Squarain KW - Oligomere KW - Polymere KW - Helix-Knäuel-Umwandlung KW - Chemische Synthese KW - Optische Spektroskopie KW - Squarain-Farbstoff KW - Helix-Knäuel-Umwandlung KW - J- and H-Aggregate KW - Optical Spectroscopy KW - Squaraine-Dye KW - J- and H-Aggregates KW - Helix-Coil-Transition Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257950 ER - TY - THES A1 - Bahndorf, Katrin T1 - Synthese und Charakterisierung von Aminosäure-basierten Amphiphilen und deren Umsetzung zu C\(_3\)-symmetrischen Sternmesogenen - Strukturkontrolle in weicher Materie über Oligopeptidaggregation T1 - Synthesis and characterization of amino-acid based amphiphiles and their conversion to C\(_3\)-symmetric star mesogens - structure control in soft matter via oligopeptide aggregation N2 - Synthese einer Bibliothek von Aminosäure-basierten Oligopeptid-Amphiphilen mittels Festphasensynthese, deren kovalente Knüpfung an einen nukleophilen Kern zu C3-symmetrischen Sternmesogenen und die Analyse der Einflüsse der verwendeten Aminosäuren auf die Sekundärstruktur des synthetisierten Moleküls. N2 - Synthesis of a library of amino acid based oligopeptide amphiphiles by solid phase synthesis, their covalent linkage to a nucleophilic core to form C3-symmetrical star mesogens and the analysis of the influences of the used amino acids on the secondary structure of the synthesized molecule. KW - Organische Chemie KW - Flüssigkristalle KW - Festphasenpeptidsynthese KW - Aminosäuren KW - Organic Chemistry KW - Liquid Crystals KW - Solid Phase Peptide Synthesis KW - Amino Acids Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-252753 ER - TY - THES A1 - Dietzsch, Julia T1 - Nucleic acid-mediated fluorescence activation and chromophore assembly T1 - Nukleinsäure-vermittelte Fluoreszenzaktivierung und Chromophorassemblierung N2 - Nucleic acids are not only one of the most important classes of macromolecules in biochemistry but also a promising platform for the defined arrangement of chromophores. Thanks to their precise organization by directional polar and hydrophobic interactions, oligonucleotides can be exploited as suitable templates for multichromophore assemblies with predictable properties. To expand the toolbox of emissive, base pairing nucleobase analogs several barbituric acid merocyanine (BAM) chromophores with tunable spectroscopic properties were synthesized and incorporated into RNA, DNA and glycol nucleic acid (GNA) oligonucleotides. A multitude of duplexes containing up to ten BAM chromophores was obtained and analysis by spectroscopic methods revealed the presence of dipolarly coupled merocyanine aggregates with properties strongly dependent on the chromophore orientation toward each other and the backbone conformation. These characteristics were exploited for various applications such as FRET pair formation and polymerase chain reaction (PCR) experiments. The observed formation of higher-order aggregates implies future applications of these new oligonucleotide-chromophore systems as light-harvesting DNA nanomaterials. Besides oligonucleotide templated covalent assembly of chromophores also non-covalent nucleic acid-chromophore complexes are a broad field of research. Among these, fluorogenic RNA aptamers are of special interest with the most versatile ones based on derivatives of the GFP chromophore hydroxybenzylidene imidazolone (HBI). Therefore, new HBI-derived chromophores with an expanded conjugated system and an additional exocyclic amino group for an enhanced binding affinity were synthesized and analyzed in complex with the Chili aptamer. Among these, structurally new fluorogenes with strong fluorescence activation upon binding to Chili were identified which are promising for further derivatization and application as color-switching sensor devices for example. N2 - Nukleinsäuren sind nicht nur eine der wichtigsten Klassen biochemisch relevanter Makromoleküle, sondern stellen auch eine vielversprechende Plattform für die definierte räumliche Organisation kleiner funktioneller Moleküle, wie beispielsweise Chromophore, dar. Oligonu-kleotide können aufgrund ihrer präzise gegliederten Struktur, die durch gerichtete polare und hydrophobe Wechselwirkungen hervorgerufen wird, als nützliche Template für die mehrfache kovalente und nicht-kovalente Anordnung von Chromophoren zu Aggregaten mit vorhersagbaren spektroskopischen Eigenschaften genutzt werden. Obwohl eine Vielzahl solcher Chromophorsysteme bereits in der Literatur beschrieben ist, basieren die meisten Chromophordesigns nur auf hydrophoben Wechselwirkungen zwischen den einzelnen Chromophoren und lassen die intrinsische Fähigkeit kanonischer Nukleobasen, komplementäre Basenpaare zu bilden, außen vor. Allerdings liegt es auf der Hand, dass die Berücksichtigung dieser polaren Wechselwirkungen nicht nur zu einer Stabilisierung der Oligonukleotid-Sekundärstruktur führen kann, sondern auch die Interpretation spektroskopischer Effekte vereinfacht. Um das bekannte Spektrum emittierender Nukleobasen-Analoga zu erweitern und den zusätz-lichen Einfluss dieser polaren Wechselwirkungen auszunutzen, wurden im Zuge dieser Arbeit verschiedene, strukturell unterschiedliche Barbitursäure-Merocyanin-Chromophore (BAM) entworfen. Die Barbitursäure-Akzeptoreinheit dieser künstlichen Nukleobasensurrogate ähnelt der Watson-Crick-Basenpaarungsseite der natürlichen T- und U-Nukleobasen und soll somit die Basenpaarung mit Adenosin ermöglichen. Durch die Kombination dieses Akzeptors mit unterschiedlich aufgebauten aromatischen Donoreinheiten, wie zum Beispiel Indol und Benzothiazol, konnten Merocyanine mit interessanten spektroskopischen Eigenschaften erhalten werden. Da die Konstitution des Nukleinsäurerückgrates einen starken Einfluss auf die Strukturparameter und die thermodynamische Stabilität der resultierenden Duplexstruktur hat, wurden die synthetisierten BAM-Chromophore in Phosphoramiditbausteine für die kovalente Assemblierung innerhalb verschiedener Oligonukleotidsysteme umgewandelt. Neben der Synthese entsprechender DNA- und RNA-Nukleotide wurden die BAM-Chromophore auch als Glykolnukleinsäure-Bausteine (GNA) mit einem azyklischen Rückgrat hergestellt. Der erfolgreiche Einbau der erhaltenen künstlichen Nukleoside konnte durch Festphasensynthese erreicht werden, wobei über 100 modifizierte Einzelstränge erhalten werden konnten. Die Hybridisierung der künstlichen Oligonukleotid-Einzelstränge mit ihren jeweiligen Gegensträngen führte zu einer Vielzahl kurzer Duplexstrukturen mit bis zu zehn BAM-Chromophoren in unterschiedlicher Anordnung. Mithilfe verschiedenster spektroskopischer Methoden konnte ein Einblick in die strukturelle Organisation der Merocyanine innerhalb dieser Systeme erhalten werden, wobei sich die Bildung dipolar-gekoppelter Merocyanin-Dimere und -Multimere zeigte. Die hierfür erforderliche ungewöhnliche \textit{syn}-Konformation der BAM-Chromophore wurde weiterhin durch Oligonukleotid-NMR bestätigt. Erstaunlicherweise wiesen die spektroskopischen und thermodynamischen Eigenschaften BAM-modifizierter Nukleinsäuren eine starke Abhängigkeit von der Chromophororientierung und der Konformation des Rückgrates auf. Dieser Effekt konnte für verschiedene Anwendungen wie die Bildung von FRET-Paaren und die Verwendung als internes fluoreszentes Stop-Nukleotid in Polymerasekettenreaktionen ausgenutzt werden. Mithilfe von Rasterkraftmikroskopie wurde außerdem die Bildung von Aggregaten höherer Ordnung beobachtet, was eine zukünftige Verwendung dieser neuen Oligonukleotid-Chromophor-Systeme als Materialien für Lichtsammelkomplexe oder für die DNA-Nanotechnologie denkbar macht. Ein weiteres großes Forschungsfeld neben kovalenten Chromophoranordnungen mit Oligonukleotiden als Templat sind nicht-kovalente Nukleinsäure-Chromophorkomplexe. Insbesondere fluorogene RNA-Aptamere sind hier von großer Bedeutung wobei die wichtigsten auf der Fluoreszenzaktivierung von Derivaten 4-Hydroxybenzylidenimidazolon-Fluorophors (HBI), dem Chromophor des natürlich vorkommenden grün fluoreszierenden Proteins (GFP), beruhen. Allerdings zeigen viele der berichteten Aptamer-Ligand-Systeme signifikante Nachteile wie unter anderem unspezifische Bindung, eine starke Tendenz zu Photoisomerisierung oder ineffiziente Zellpermeabilität. Deshalb wurden im Zuge dieser Arbeit neue, von HBI abgeleitete Chromophore mit einem vergrößerten konjugierten $\uppi$-System und einer zusätzlichen exozykli-schen Aminogruppe für eine erhöhte Bindungsaffinität synthetisiert und im Komplex mit dem bekannten Chili-Aptamer untersucht. Einige dieser strukturell neuen Chromophore zeigten einen starken Anstieg der Emission bei Bindung an dieses Aptamer und wurden daher weiter charakterisiert. Sie stellen eine vielversprechende Möglichkeit für weitere Derivatisierung und die zukünftige Anwendung beispielsweise als schaltbare Aptamer-basierte Fluoreszenzsensoren dar. KW - Nucleinsäuren KW - Merocyanine KW - Grün fluoreszierendes Protein KW - Aptamer KW - Exziton KW - Fluoreszenzaktivierung Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259761 ER - TY - THES A1 - Bold, Kevin T1 - Macrocyclic Oligothiophene Bridged Perylene Bisimide Donor−Acceptor Dyads T1 - Makrozyklische Oligothiophen-überbrückte Perylenbisimid Donor-Akzeptor Dioden N2 - A series of donor-acceptor macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide have been synthesized via a platinum-mediated cross-coupling strategy. The target structures were characterized by steady-state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Crystal structure analysis of the macrocycles revealed insights into the bridge arrangements. The properties of the macrocyclic bridges were compared to linear oligothiophene reference compounds which itself exhibited an unusual electrochemical effect. N2 - In der vorliegenden Dissertation wurde eine Reihe von Donor-Akzeptor Makrozyklen bestehend aus Oligothiophensträngen, welche die Imid-Positionen eines Perylenbisimids kovalent verbinden, in einer Platin-vermittelten Kreuzkupplungsreaktion synthetisiert. Die Zielstrukturen wurden anschließend mittels UV/Vis-, Fluoreszenz-und transienter Absorptionsspektroskopie, sowie zyklischer- bzw. Differential-Puls-Voltammetry charakterisiert. Ferner gewährten Kristallstrukturen von drei der insgesamt fünf Makrozyklen strukturelle Einblicke in die Oligothiophen-Brückengeometrie. Die photophysikalischen und elektrochemischen Eigenschaften der makrozyklischen Brücken wurden mit solchen linearer Oligothiophen-Referenzsystemen verglichen, welche selber ein ungewöhnliches Phänomen in der Elektrochemie aufwiesen. KW - Perylenbisdicarboximide KW - Makrocyclische Verbindungen KW - Thiophen KW - Farbstoff KW - donor-acceptor dyads KW - macrocycles KW - electron transfer KW - perylene bisimide KW - oligothiophenes Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-271926 ER - TY - JOUR A1 - Noll, Niklas A1 - Krause, Ana-Maria A1 - Beuerle, Florian A1 - Würthner, Frank T1 - Enzyme-like water preorganization in a synthetic molecular cleft for homogeneous water oxidation catalysis JF - Nature Catalysis N2 - Inspired by the proficiency of natural enzymes, mimicking of nanoenvironments for precise substrate preorganisation is a promising strategy in catalyst design. However, artificial examples of enzyme-like activation of H\(_2\)O molecules for the challenging oxidative water splitting reaction are hardly explored. Here, we introduce a mononuclear Ru(bda) complex (M1, bda: 2,2’-bipyridine-6,6’-dicarboxylate) equipped with a bipyridine-functionalized ligand to preorganize H\(_2\)O molecules in front of the metal center as in enzymatic clefts. The confined pocket of M1 accelerates chemically driven water oxidation at pH 1 by facilitating a water nucleophilic attack pathway with a remarkable turnover frequency of 140 s\(^{−1}\) that is comparable to the oxygen-evolving complex of photosystem II. Single crystal X-ray analysis of M1 under catalytic conditions allowed the observation of a 7th H\(_2\)O ligand directly coordinated to a RuIII center. Via a well-defined hydrogen-bonding network, another H\(_2\)O substrate is preorganized for the crucial O–O bond formation via nucleophilic attack. KW - water oxidation KW - enzyme KW - catalysis KW - molecular KW - catalyst synthesis KW - catalytic mechanisms KW - homogeneous catalysis KW - photocatalysis KW - supramolecular chemistry Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-302897 N1 - This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use (https://www.springernature.com/gp/open-research/policies/accepted-manuscript-terms), but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1038/s41929-022-00843-x ET - accepted version ER - TY - JOUR A1 - Fayez, Shaimaa A1 - Bruhn, Torsten A1 - Feineis, Doris A1 - Assi, Laurent Aké A1 - Kushwaha, Prem Prakash A1 - Kumar, Shashank A1 - Bringmann, Gerhard T1 - Naphthylisoindolinone alkaloids: the first ring-contracted naphthylisoquinolines, from the tropical liana Ancistrocladus abbreviatus, with cytotoxic activity JF - RSC Advances N2 - The West African liana Ancistrocladus abbreviatus is a rich source of structurally most diverse naphthylisoquinoline alkaloids. From its roots, a series of four novel representatives, named ancistrobrevolines A–D (14–17) have now been isolated, displaying an unprecedented heterocyclic ring system, where the usual isoquinoline entity is replaced by a ring-contracted isoindolinone part. Their constitutions were elucidated by 1D and 2D NMR and HR-ESI-MS. The absolute configurations at the chiral axis and at the stereogenic center were assigned by using experimental and computational electronic circular dichroism (ECD) investigations and a ruthenium-mediated oxidative degradation, respectively. For the biosynthetic origin of the isoindolinones from ‘normal’ naphthyltetrahydroisoquinolines, a hypothetic pathway is presented. It involves oxidative decarboxylation steps leading to a ring contraction by a benzilic acid rearrangement. Ancistrobrevolines A (14) and B (15) were found to display moderate cytotoxic effects (up to 72%) against MCF-7 breast and A549 lung cancer cells and to reduce the formation of spheroids (mammospheres) in the breast cancer cell line. KW - Naphthylisoindolinone alkaloids Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300766 VL - 12 IS - 45 ER - TY - JOUR A1 - Kleiber, Nicole A1 - Lemus-Diaz, Nicolas A1 - Stiller, Carina A1 - Heinrichs, Marleen A1 - Mong-Quyen Mai, Mandy A1 - Hackert, Philipp A1 - Richter-Dennerlein, Ricarda A1 - Höbartner, Claudia A1 - Bohnsack, Katherine E. A1 - Bohnsack, Markus T. T1 - The RNA methyltransferase METTL8 installs m\(^3\)C\(_{32}\) in mitochondrial tRNAs\(^{Thr/Ser(UCN)}\) to optimise tRNA structure and mitochondrial translation JF - Nature Communication N2 - Modified nucleotides in tRNAs are important determinants of folding, structure and function. Here we identify METTL8 as a mitochondrial matrix protein and active RNA methyltransferase responsible for installing m\(^3\)C\(_{32}\) in the human mitochondrial (mt-)tRNA\(^{Thr}\) and mt-tRNA\(^{Ser(UCN)}\). METTL8 crosslinks to the anticodon stem loop (ASL) of many mt-tRNAs in cells, raising the question of how methylation target specificity is achieved. Dissection of mttRNA recognition elements revealed U\(_{34}\)G\(_{35}\) and t\(^6\)A\(_{37}\)/(ms\(^2\))i\(^6\)A\(_{37}\), present concomitantly only in the ASLs of the two substrate mt-tRNAs, as key determinants for METTL8-mediated methylation of C\(_{32}\). Several lines of evidence demonstrate the influence of U\(_{34}\), G\(_{35}\), and the m\(^3\)C\(_{32}\) and t\(^6\)A\(_{37}\)/(ms\(^2\))i\(^6\)A\(_{37}\) modifications in mt-tRNA\(^{Thr/Ser(UCN)}\) on the structure of these mt-tRNAs. Although mt-tRNA\(^{Thr/Ser(UCN)}\) lacking METTL8-mediated m\(^3\)C\(_{32}\) are efficiently aminoacylated and associate with mitochondrial ribosomes, mitochondrial translation is mildly impaired by lack of METTL8. Together these results define the cellular targets of METTL8 and shed new light on the role of m\(^3\)C\(_{32}\) within mt-tRNAs. KW - Modified Nucleotides in tRNAs KW - METTL8 KW - Mitochondrial Matrix Protein KW - RNA Methyltransferase KW - RNA KW - Enzymes KW - Organelles Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-254592 VL - 13 ER - TY - JOUR A1 - Hong, Yongseok A1 - Kim, Woojae A1 - Kim, Taeyeon A1 - Kaufmann, Christina A1 - Kim, Hyungjun A1 - Würthner, Frank A1 - Kim, Dongho T1 - Real-time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda-dimer by Ultrafast Time-Domain Raman Spectroscopy JF - Angewandte Chemie International Edition N2 - In π-conjugated organic photovoltaic materials, an excimer state has been generally regarded as a trap state which hinders efficient excitation energy transport. But despite wide investigations of the excimer for overcoming the undesirable energy loss, the understanding of the relationship between the structure of the excimer in stacked organic compounds and its properties remains elusive. Here, we present the landscape of structural dynamics from the excimer formation to its relaxation in a co-facially stacked archetypical perylene bisimide folda-dimer using ultrafast time-domain Raman spectroscopy. We directly captured vibrational snapshots illustrating the ultrafast structural evolution triggering the excimer formation along the interchromophore coordinate on the complex excited-state potential surfaces and following evolution into a relaxed excimer state. Not only does this work showcase the ultrafast structural dynamics necessary for the excimer formation and control of excimer characteristics but also provides important criteria for designing the π-conjugated organic molecules. KW - excimer KW - vibrational coherence KW - time-resolved impulsive stimulated raman spectroscopy KW - structural dynamics KW - perylene bisimide Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318788 VL - 61 IS - 13 ER - TY - JOUR A1 - Mützel, Carina A1 - Farrell, Jeffrey M. A1 - Shoyama, Kazutaka A1 - Würthner, Frank T1 - 12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon JF - Angewandte Chemie International Edition N2 - Herein we devise and execute a new synthesis of a pristine boron-doped nanographene. Our target boron-doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B-doping arrangement. Our synthesis of this target, a doubly B-doped hexabenzopentacene (B\(_{2}\)-HBP), employs six net C−H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr\(_{3}\)/AlCl\(_{3}\)/2,6-dichloropyridine-mediated C−H borylation steps. As predicted by our calculations, B\(_{2}\)-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B\(_{2}\)-HBP possesses a very low LUMO level, showing two reversible reductions at −1.00 V and −1.17 V vs. Fc\(^{+}\)/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B-doped polycyclic aromatic hydrocarbons. KW - aromaticity KW - polycycles KW - pentacene KW - near infrared emitter KW - boron Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318808 VL - 61 IS - 8 ER - TY - JOUR A1 - Liu, Bin A1 - Vonhausen, Yvonne A1 - Schulz, Alexander A1 - Höbartner, Claudia A1 - Würthner, Frank T1 - Peptide Backbone Directed Self-Assembly of Merocyanine Oligomers into Duplex Structures JF - Angewandte Chemie International Edition N2 - The pseudopeptide backbone provided by N-(2-aminoethyl)-glycine oligomers with attached nucleobases has been widely utilized in peptide nucleic acids (PNAs) as DNA mimics. Here we demonstrate the suitability of this backbone for the formation of structurally defined dye stacks. Toward this goal a series of peptide merocyanine (PMC) dye oligomers connected to a N-(2-aminoethyl)-glycine backbone were prepared through peptide synthesis. Our concentration-, temperature- and solvent-dependent UV/Vis absorption studies show that under the control of dipole–dipole interactions, smaller-sized oligomers consisting of one, two or three dyes self-assemble into defined duplex structures containing two up to six chromophores. In contrast, upon further extension of the oligomer, the chosen peptide backbone cannot direct the formation of a defined duplex architecture anymore due to intramolecular aggregation between the dyes. For all aggregate species a moderate aggregation-induced emission enhancement is observed. KW - dipole-dipole interaction KW - peptide backbone KW - merocyanine KW - dye assembly KW - duplex structure Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318797 VL - 61 IS - 21 ER - TY - JOUR A1 - Ouyang, Guanghui A1 - Rühe, Jessica A1 - Zhang, Yang A1 - Lin, Mei-Jin A1 - Liu, Minghua A1 - Würthner, Frank T1 - Intramolecular Energy and Solvent-Dependent Chirality Transfer within a BINOL-Perylene Hetero-Cyclophane JF - Angewandte Chemie International Edition N2 - Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay-substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well-defined geometry, we report a chiral PBI hetero-cyclophane (BBI-PBI) that shows intramolecular energy and solvent-regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80–98 %) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI. KW - chirality transfer KW - solvent effects KW - perylene bisimide KW - energy transfer KW - cyclophanes Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318818 VL - 61 IS - 31 ER - TY - JOUR A1 - Scheidel, Sebastian A1 - Östreicher, Laurina A1 - Mark, Isabelle A1 - Pöppler, Ann-Christin T1 - You cannot fight the pressure: Structural rearrangements of active pharmaceutical ingredients under magic angle spinning JF - Magnetic Resonance in Chemistry N2 - Although solid-state nuclear magnetic resonance (NMR) is a versatile analytical tool to study polymorphs and phase transitions of pharmaceutical molecules and products, this work summarizes examples of spontaneous and unexpected (and unwanted) structural rearrangements and phase transitions (amorphous-to-crystalline and crystalline-to-crystalline) under magic angle spinning (MAS) conditions, some of them clearly being due to the pressure experienced by the samples. It is widely known that such changes can often be detected by X-ray powder diffraction (XRPD); here, the capability of solid-state NMR experiments with a special focus on \(^{1}\)H-\(^{13}\)C frequency-switched Lee–Goldburg heteronuclear correlation (FSLG HETCOR)/MAS NMR experiments to detect even subtle changes on a molecular level not observable by conventional 1D NMR experiments or XRPD is presented. Furthermore, it is shown that a polymorphic impurity combined with MAS can induce a crystalline-to-crystalline phase transition. This showcases that solid-state NMR is not always noninvasive and such changes upon MAS should be considered in particular when compounds are studied over longer time spans. KW - \(^{1}\)H-\(^{13}\)C HETCOR KW - API KW - structural changes KW - XRPD KW - solid-state NMR KW - MAS Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318838 VL - 60 IS - 6 SP - 572 EP - 582 ER - TY - JOUR A1 - Schulz, Alexander A1 - Würthner, Frank T1 - Folding-induced fluorescence enhancement in a series of merocyanine hetero-folda-trimers JF - Angewandte Chemie International Edition N2 - Many dyes suffer from fast non-radiative decay pathways, thereby showing only short-lived excited states and weak photoluminescence. Here we show a pronounced fluorescence enhancement for a weakly fluorescent merocyanine (MC) dye by being co-facially stacked to other dyes in hetero-folda-trimer architectures. By means of fluorescence spectroscopy (lifetime, quantum yield) the fluorescence enhancement was explained by the rigidification of the emitting chromophore in the defined foldamer architecture and the presence of a non-forbidden lowest exciton state in H-coupled hetero-aggregates. This folding-induced fluorescence enhancement (FIFE) for specific sequences of π-stacked dyes points at a viable strategy toward improved fluorophores that relates to the approach used by nature in the green fluorescent protein (GFP). KW - organic chemistry KW - merocyanines KW - aggregation KW - dyes/pigments KW - fluorescence KW - folding Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256582 VL - 61 IS - 2 ER - TY - INPR A1 - Scheitl, Carolin P. M. A1 - Mieczkowski, Mateusz A1 - Schindelin, Hermann A1 - Höbartner, Claudia T1 - Structure and mechanism of the methyltransferase ribozyme MTR1 T2 - Nature Chemical Biology N2 - RNA-catalysed RNA methylation was recently shown to be part of the catalytic repertoire of ribozymes. The methyltransferase ribozyme MTR1 catalyses the site-specific synthesis of 1-methyladenosine (m\(^1\)A) in RNA, using O\(^6\)-methylguanine (m\(^6\)G) as methyl group donor. Here we report the crystal structure of MTR1 at a resolution of 2.8 Å, which reveals a guanine binding site reminiscent of natural guanine riboswitches. The structure represents the postcatalytic state of a split ribozyme in complex with the m1A-containing RNA product and the demethylated cofactor guanine. The structural data suggest the mechanistic involvement of a protonated cytidine in the methyl transfer reaction. A synergistic effect of two 2'-O-methylated ribose residues in the active site results in accelerated methyl group transfer. Supported by these results, it seems plausible that modified nucleotides may have enhanced early RNA catalysis and that metabolite-binding riboswitches may resemble inactivated ribozymes that have lost their catalytic activity during evolution. KW - Methyltransferase Ribozyme MTR1 KW - Crystal structure of MTR1 KW - RNA-catalyzed RNA methylation KW - X-ray crystallography KW - RNA Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-272170 ET - submitted version ER - TY - INPR A1 - Sednev, Maksim V. A1 - Liaqat, Anam A1 - Höbartner, Claudia T1 - High-Throughput Activity Profiling of RNA-Cleaving DNA Catalysts by Deoxyribozyme Sequencing (DZ-seq) T2 - Journal of the American Chemical Society N2 - RNA-cleaving deoxyribozymes have found broad application as useful tools for RNA biochemistry. However, tedious in vitro selection procedures combined with laborious characterization of individual candidate catalysts hinder the discovery of novel catalytic motifs. Here, we present a new high-throughput sequencing method, DZ-seq, which directly measures activity and localizes cleavage sites of thousands of deoxyribozymes. DZ-seq exploits A-tailing followed by reverse transcription with an oligo-dT primer to capture the cleavage status and sequences of both deoxyribozyme and RNA substrate. We validated DZ-seq by conventional analytical methods and demonstrated its utility by discovery of novel deoxyribozymes that allow for cleaving challenging RNA targets or the analysis of RNA modification states. KW - RNA-Cleaving Deoxyribozymes KW - High-Throughput Sequencing Method, DZ-seq KW - Analysis of RNA Modifications Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258520 ER - TY - THES A1 - Smolan, Willi T1 - Linear Multifunctional PEG-Alternatives for Bioconjugation and Hydrogel Formation T1 - Lineare Multifunktionelle PEG-Alternativen für Biokonjugation und Hydrogelbildung N2 - The objective of this thesis was the synthesis and characterisation of two linear multifunctional PEG-alternatives for bioconjugation and hydrogel formation: i) Hydrophilic acrylate based copolymers containing peptide binding units and ii) hydrophilic polyether based copolymers containing different functional groups for a physical crosslinking. In section 3.1 the successful synthesis of water soluble and linear acrylate based polymers containing oligo(ethylene glycol) methyl ether acrylate with either linear thioester functional 2-hydroxyethyl acrylate, thiolactone acrylamide, or vinyl azlactone via the living radical polymerisation technique Reversible Addition Fragmentation Chain Transfer (RAFT) and via free-radical polymerisation is described. The obtained polymers were characterized via GPC, 1H NMR, IR and RAMAN spectroscopy. The RAFT end group was found to be difficult to remove from these short polymer chains and accordingly underwent the undesired side reaction aminolysis with the peptide during the conjugation studies. Besides that, polymers without RAFT end groups did not show any binding of the peptide at the thioester groups, which can be improved in future by using higher reactant concentrations and higher amount of binding units at the polymer. Polymers containing the highly reactive azlactone group showed a peptide binding of 19 %, but unfortunately this function also underwent spontaneous hydrolysis before the peptide could even be bound. In all cases, oligo(ethylene glycol) methyl ether acrylate was used with a relatively high molecular weight (Mn = 480 Da) was used, which eventually was efficiently shielding the introduced binding units from the added peptide. In future, a shorter monomer with Mn = 300 Da or less or hydrophilic N,N’-dialkyl acrylamide based polymers with less steric hindrance could be used to improve this bioconjugation system. Additionally, the amount of monomers containing peptide binding units in the polymer can be increased and have an additional spacer to achieve higher loading efficiency. The water soluble, linear and short polyether based polymers, so called polyglycidols, were successfully synthesized and modified as described in section 3.2. The obtained polymers were characterized using GPC, 1H NMR, 31P{1H} NMR, IR, and RAMAN spectroscopy. The allyl groups which were present up to 20 % were used for radical induced thiol-ene chemistry for the introduction of functional groups intended for the formation of the physically crosslinking hydrogels. For the positively charged polymers, first a chloride group had to be introduced for the subsequent nucleophilic substitution with the imidazolium compound. There, degrees of modifications were found in the range 40-97 % due to the repulsion forces of the charges, decreased concentration of active chloride groups, and limiting solution concentrations of the polymer for this reaction. For the negatively charged polymers, first a protected phosphonamide moiety was introduced with a deprotection step afterwards showing 100 % conversion for all reactions. Preliminary hydrogel tests did not show a formation of a three-dimensional network of the polymer chains which was attributed to the short backbone length of the used polymers, but the gained knowledge about the synthetic routes for the modification of the polymer was successfully transferred to longer linear polyglycidols. The same applies to the introduction of electron rich and electron poor compounds showing π-π stacking interactions by UV-vis spectroscopy. Finally, long linear polyglycidyl ethers were synthesised successfully up to molecular weights of Mn ~ 30 kDa in section 3.3, which was also proven by GPC, 1H NMR, IR and RAMAN spectroscopy. This applies to the homopolymerisation of ethoxyethyl glycidyl ether, allyl glycidyl ether and their copolymerisation with an amount of the allyl compound ~ 10 %. Attempts for higher molecular weights up to 100 kDa showed an uncontrolled polymerisation behaviour and eventually can be improved in future by choosing a lower initiation temperature. Also, the allyl side groups were modified via radical induced thiol-ene chemistry to obtain positively charged functionalities via imidazolium moieties (85 %) and negatively charged functionalities via phosphonamide moieties (100 %) with quantitative degree of modifications. Hydrogel tests have still shown a remaining solution by using long linear polyglycidols carrying negative charges with long/short linear polyglycidols carrying positive charges. The addition of calcium chloride led to a precipitate of the polymer instead of a three-dimensional network formation representing a too high concentration of ions and therefore shielding water molecules with prevention from dissolving the polymer. These systems can be improved by tuning the polymers structure like longer polymer chains, longer spacer between polymer backbone and charge, and higher amount of functional groups. The objective of the thesis was partly reached containing detailed investigated synthetic routes for the design and characterisation of functional polymers which could be used in future with improvements for bioconjugation and hydrogel formation tests. N2 - Das Ziel dieser Arbeit war es zwei lineare multifunktionale PEG-Alternativen für die Bioconjugation und Hydrogelbildung herzustellen und zu charakterisieren: i) Wasserlösliche Acrylat-basierte Copolymere mit Peptidbindungseinheiten und ii) wasserlösliche Polyether-basierte Copolymere mit verschiedenen funktionalen Gruppen für eine physikalische Vernetzung. In Abschnitt 3.1 wurde die erfolgreiche Synthese von wasserlöslichen und linearen Acrylat-basierten Polymeren, die Oligo(ethylen glycol) methyl ether acrylat mit jeweils 2-Hydroxyethyl acrylate modifiziert mit linearem Thioester, Thiolactonacrylamid und Vinylazlacton enthielten, mittels der lebenden Polymerisationstechnik Reversible Additions-Fragmentierungs Kettenübertragung (RAFT) und mittels freier radikalischer Polymerisation durch GPC, 1H NMR, IR und RAMAN Spektroskopie bewiesen. Es erwies sich als schwer die RAFT-Endgruppe von den kurzen Polymerketten zu entfernen und führte zur Nebenreaktion Aminolyse mit dem Peptid während des Konjugationsprozesses. Außerdem zeigten Polymere ohne RAFT-Endgruppen keine Peptidbindung an den Thioestergruppen, was durch höhere Konzentration der Reaktanten und größeren Anteil an Peptidbindungseinheiten am Polymer in Zukunft verbessert werden könnte. Polymere mit Azlaktongruppen zeigten eine Bindung von 19 %, wobei dies eine sehr reaktive Gruppe ist und vor der Peptidbindung noch hydrolysieren kann. In allen Fällen wurde Oligo(ethylen glycol) methyl ether acrylat mit Mn = 480 Da verwendet, welches die Peptidbindungsstellen abschirmen kann. Daher können in Zukunft Monomere mit Mn = 300 Da oder N,N’-Dialkylacrylamid-basierte Monomere mit weniger sterischer Hinderung für dieses System verwendet werden. Zusätzlich kann der Anteil an Monomeren mit Peptidbindungseinheiten im Polymer und zusätzlicher Seitenkette erhöht werden, um höhere Bindungseffektivitäten zu erreichen. Die erfolgreiche Synthese und Modifikation von wasserlöslichen, linearen und kurzen Polyether-basierten Polymeren, sogenannten Polyglycidolen, konnte in Abschnitt 3.2 mittels GPC, 1H NMR, 31P{1H} NMR, IR und RAMAN Spektroskopie bewiesen werden. Die Allylgruppe, die bis zu 20 % vorhanden war, wurde für die radikalisch induzierte Thiol-En Chemie zur Einführung von funktionellen Gruppen verwendet. Für die positiv geladenen Polymere, wurde zuerst eine Chloridgruppe generiert, die anschließend für die nukleophile Substitution mit einer Imidazolkomponente verwendet wurde. Dabei wurden Substitutionsgrade von 40-97 % gefunden, was an den Abstoßungskräften der Ladungen, verringerter Konzentration der aktiven Chloridgruppen und der begrenzten Löslichkeitskonzentration bei dieser Reaktion liegt. Für die negativ geladenen Polymere wurde zuerst eine geschützte Phosphonamidgruppe eingeführt, die anschließend entschützt wurde und bei allen Reaktionen einen Umsatz von 100 % zeigte. Vorläufige Hydrogeltests zeigten keine Bildung eines dreidimensionales Netzwerks der Polymerketten aber es wurden Erkenntnisse über die synthetischen Routen für die Modifikation der Polymere für den Transfer auf lange lineare Polyglycidole gewonnen. Das gleiche gilt für die Einführung von elektronreichen und elektronarmen Komponenten, die eine π-π Stapelwechselwirkung mittels UV-vis Spektroskopie zeigte. Letztlich wurden lange lineare Polyglycidole bis zu Molmassen von Mn ~ 30 kDa erfolgreich in Abschnitt 3.3 hergestellt und mittels GPC, 1H NMR, IR and RAMAN Spektroskopie bewiesen. Dies gilt für die Homopolymerisation von Ethoxyethyl glycidyl ether, Ally glycidyl ether und deren Copolymerisation mit einem Anteil der Allylkomponente von ~ 10 %. Versuche um höhere Molekulargewichte bis zu 100 kDa zeigten ein unkontrolliertes Polymerisationsverhalten, welches durch eine niedrigere Initiierungstemperatur weiter verbessert werden kann. Ebenso wurden die Allylseitengruppen mittels radikalisch induzierter Thiol-En Chemie modifiziert, um positivgeladene Funktionalitäten durch Imidazolgruppen (85 %) und negativgeladene Funktionalitäten durch Phosphonamidgruppen (100 %) in quantitativen Umsätzen einzuführen. Hydrogeltests von langen linearen Polyglycidolen, die negativ geladene Gruppen haben, mit langen/kurzen linearen Polyglycidolen, die positiv geladene Gruppen haben, haben eine verbleibende Lösung gezeigt. Die Zugabe von Calciumchlorid führte zum Ausfall des Polymers anstatt zu einem dreidimensionalen Netzwerk repräsentiert durch eine zu hohe Ionenkonzentration. Dies führte zu einer Abschirmung der Wassermoleküle vom Polymer und verhinderte, dies aufzulösen. Das System kann verbessert werden, indem die Polymerstruktur variiert wird, z.B. durch längere Polymerketten, größere Abstände zwischen Polymerhauptkette und Ladung und einen größeren Anteil an funktionellen Gruppen. Das Ziel der Arbeit wurde teilweise erreicht, welches detailliert untersuchte Syntheserouten für das Design und die Charakterisierung von funktionellen Polymeren beinhaltet, welche in Zukunft mit Verbesserungen für Bioconjuations- und Hydrogelformulierungstests verwendet werden können. KW - Wasserlösliche Polymere KW - Ringöffnungspolymerisation KW - Hydrogel KW - polyglycidol KW - RAFT KW - polymer-peptide-conjugate KW - ring opening polymerisation KW - thiol-ene Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-278734 ER - TY - JOUR A1 - Full, Felix A1 - Wölflick, Quentin A1 - Radacki, Krzysztof A1 - Braunschweig, Holger A1 - Nowak‐Król, Agnieszka T1 - Enhanced Optical Properties of Azaborole Helicenes by Lateral and Helical Extension JF - Chemistry – A European Journal N2 - The synthesis and characterization of laterally extended azabora[5]‐, ‐[6]‐ and ‐[7]helicenes, assembled from N‐heteroaromatic and dibenzo[g,p]chrysene building blocks is described. Formally, the π‐conjugated systems of the pristine azaborole helicenes were enlarged with a phenanthrene unit leading to compounds with large Stokes shifts, significantly enhanced luminescence quantum yields (Φ) and dissymmetry factors (g\(_{lum}\)). The beneficial effect on optical properties was also observed for helical elongation. The combined contributions of lateral and helical extensions resulted in a compound showing green emission with Φ of 0.31 and |g\(_{lum}\)| of 2.2×10\(^{−3}\), highest within the series of π‐extended azaborahelicenes and superior to emission intensity and chiroptical response of its non‐extended congener. This study shows that helical and lateral extensions of π‐conjugated systems are viable strategies to improve features of azaborole helicenes. In addition, single crystal X‐ray analysis of configurationally stable [6]‐ and ‐[7]helicenes was used to provide insight into their packing arrangements. KW - azaborole KW - circularly polarized luminescence KW - fluorescence KW - helicene KW - π-extension Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293671 VL - 28 IS - 62 ER - TY - JOUR A1 - Wu, Zhu A1 - Dinkelbach, Fabian A1 - Kerner, Florian A1 - Friedrich, Alexandra A1 - Ji, Lei A1 - Stepanenko, Vladimir A1 - Würthner, Frank A1 - Marian, Christel M. A1 - Marder, Todd B. T1 - Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature JF - Chemistry—A European Journal N2 - Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T\(^M_1\) state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T\(^A_1\) state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently. KW - AIE KW - luminescence KW - phosphorescence KW - triarylborane KW - triplet Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318297 VL - 28 IS - 30 ER - TY - JOUR A1 - Wu, Zhu A1 - Roldao, Juan Carlos A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Ferger, Matthias A1 - Würthner, Frank A1 - Gierschner, Johannes A1 - Marder, Todd B. T1 - Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP) JF - Angewandte Chemie N2 - Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)\(_{3}\) does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP. KW - boric acid KW - room-temperature phosphorescence (RTP) KW - optical materials Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318308 VL - 61 IS - 15 ER - TY - THES A1 - Liaqat, Anam T1 - Artificial Evolution of Nucleic Acid Catalysts and their Use for Studying RNA T1 - Artifizielle Evolution von katalytischen Nucleinsäuren und deren Anwendung für die Untersuchung von RNA N2 - RNA molecules play diverse roles in biological systems. Post-transcriptional RNA modifications and dynamic structures enhance the functional diversity of RNA. A prerequisite for studying their biological significance is the availability of reliable methods for the detection of RNA modifications and structures. Several promising approaches have been developed in the last few decades; however, efficient, and versatile tools are still required to study the dynamic features of RNA. This thesis focuses on the development of nucleic acid catalysts as a tool to address the current needs in studying RNA. The major part of this thesis aimed at the development of deoxyribozymes as a tool for the detection of RNA modifications. Using in vitro selection from a random DNA library, we found deoxyribozymes that are sensitive to N 6 -isopentenyladenosine (i6A), a native tRNA modification and structural analogue of m6A. The in vitro evolution identified three classes of DNA enzymes: AA, AB08, and AC17 DNAzymes that showed distinct response to i6A modification and showed strong discrimination between structural analogues, i.e., m6A and i6A. In the continuation of the project, we attempted to develop RNA-cleaving deoxyribozymes that differentially respond to monomethylated cytidine isomers, 3-methylcytidine (m3C), N4 - methylcytidine (m4C), and 5-methylcytidine (m5C). Several deoxyribozymes were identified from in vitro selection, which are selective for a specific methylated cytidine isomer. The characterization of AL112, AM101, AN05, and AK104 catalysts confirmed the successful evolution of modification-specific and general deoxyribozymes that showed a broad substrate scope. In order to accelerate the DNAzymes discovery, a high throughput sequencing method (DZ-seq) was established that directly quantifies the RNA cleavage activity and cleavage site from deep sequencing data. The libraries contained information about cleavage status, cleavage site and sequence of deoxyribozymes and RNA substrate. The fraction cleaved (FC) data obtained from Dz-seq was validated for a subset of deoxyribozmes using conventional gel based kinetic assay and showed a good linear correlation (R2 = 0.91). Dz-seq possesses a great potential for the discovery of novel deoxyribozymes for the analysis of various RNA modifications in the future. The second objective of the current study was the development of structure-specific RNA labeling ribozymes. Here, we attempted to develop ribozymes that targets RNA of interest by structure-specific interaction rather than base-pairing and focused on a specific RNA G-quadruplex as the target. Two subsequent selection experiments led to the identification of the adenylyltransferase ribozymes AO10.2 and AR9. The partial characterization of these catalysts showed that A010.2 was unable to recognize intact BCL2 structure, but it turned out as the first reported trans-active ribozyme that efficiently labeled uridine in a defined substrate RNA hybridized to the ribozyme. The other ribozyme AR9 was shown to serve as a trans-active, self-labeling ribozyme that catalyzed adenylyl transferase reaction in the presence of the intact BCL2 sequence. Based on these preliminary findings, we envision that AR9 could potentially serve as a reporter RNA by self-labeling in the presence of an RNA G-quadruplex. However, both AO10.2 and AR9 still require more detailed characterization for their potential applications. N2 - RNA hat zahlreiche Funktionen in verschiedensten biologischen Systemen. Sowohl posttranskriptionelle Modifikationen als auch die Dynamik der dreidimensionalen Struktur von RNA trägt zu deren funktionalen Diversität bei. Eine Voraussetzung, um die biologische Bedeutung von RNA genauer zu untersuchen, ist die Verfügbarkeit zuverlässiger Methoden zur Detektion von RNA-Modifikationen und -Strukturen. In den letzten Jahrzenten wurden hierfür zahlreiche vielversprechende Ansätze entwickelt und berichtet. Allerdings besteht weiterhin der Bedarf an effizienten und vielseitig einsetzbaren Hilfsmitteln, um die Dynamik von RNA weiter zu erforschen. Diese Arbeit konzentriert sich auf die Entwicklung von Nucleinsäure basierten Katalysatoren, die in Zukunft als Werkzeug zur Untersuchung von RNA eingesetzt werden können. Der Großteil dieser Arbeit strebte die Entwicklung von Desoxyribozymen als Werkzeug für die Detektion von RNA-Modifikation an. Vor kurzem wurden m6A-sensitive DNA-Enzyme berichtet, die RNA schneiden können und damit Auskunft über deren Methylierungs-Status geben können. Diese sind auch in der Lage m6A in natürlichen RNAs wie lncRNAs und C/D box snoRNAs zu detektieren. Allerdings fehlen detaillierten strukturelle und mechanistische Erkenntnissen darüber, wie Desoxyribozyme solche Modifikationen detektieren. Deshalb ist es noch nicht möglich bereits vorhandene DNA-Enzyme umzuarbeiten, damit diese auch andere RNA-Modifikationen erkennen können. Aus diesem Grund fokussierten wir uns hier auf die Entwicklung neuer DNA-Enzyme für die Detektion von RNA-Modifikationen über m6A hinaus. Mit Hilfe von in vitro Selektion konnten wir ausgehend von einer randomisierten DNA-Bibliothek, Desoxyribozyme finden, die sensitiv gegenüber N6-Isopentenyladenosin (i6A) sind. Bei dieser Modifikation handelt es sich um ein strukturelles Analogon von m6A, die natürlicherweise in tRNA vorkommt. Als Ergebnis der in vitro Selektion konnten drei Klassen an DNA-Enzymen identifiziert werden: AA, AB08 und AC17 Desoxyribozyme. AA DNA-Enzyme spalteten unmodifizierte RNA und wurden durch i6A stark inhibiert. AB08 schnitten i6A-modifizierte RNA signifikant schneller als unmodifizierte RNA. Im Gegensatz hierzu zeigte AC17 ein einzigartiges Verhalten, indem es die Schneide-Position innerhalb der RNA um ein Nukleotid Richtung 5‘-Ende verschob, wenn eine i6A-Modifikation vorhanden war. Des weiteren konnten alle drei Klassen an DNA-Enzymen eindeutig zwischen m6A und i6A unterscheiden. Im weiteren Verlauf des Projektes strebten wir an RNA-schneidente Desoxyribozyme zu entwickeln, die die mono-methylierten Cytidin-Isomere 3-Methylcytidin (m3C), N4-Methylcytidin (m4C) und 5-Methylcytidine (m5C) voneinander unterscheiden können. Um vielseitigere DNA-Enzyme zu erhalten, benutzten wir RNA-Substrate, die ein randomisiertes Nukleotid in 5‘-Richtung neben dem methylierten Cytidin besaßen. Mehrere Desoxyribozyme konnten identifiziert werden, die selektiv und spezifisch für eines der methylierten Cytidin Isomere waren. Die Charakterisierung der DNA-Enzyme AL112, AM101, AN05 und AK104 bestätigte die erfolgreiche Evolution von einerseits modifikations-spezifischen sowie aber auch generellen DNA-Enzymen, die einen großen Substrat-Bereich abdecken. Zudem konnte gezeigt werden, dass AL112, AN05 und AK104 als programmierbare Werkzeuge zur Bestätigung von m3C- und m5C-Modifikationen in menschlicher mitochondrialen tRNA eingesetzt werden können. Um die Entdeckung von DNA-Enzymen weiter zu beschleunigen, wurde eine Hochdurchsatz-Sequenzierungsmethode (DZ-seq) entwickelt. Diese nutzt die Sequenzierungsdaten, um direkt die Schneideaktivität einzelner Desoxyribozyme zu quantifizieren sowie die genaue Stelle der RNA-Spaltung festzustellen. Illumina Sequenzierungsbibliotheken wurden ausgehend von aktiven DNA-Pools hergestellt, welche an bestimmte RNA-Substrate ligiert wurden. Nachdem die Schneide-Reaktion stattgefunden hatte, wurden sowohl die geschnittenen als auch die ungeschnittenen Fraktionen mit Hilfe von Poly(A)-Polymerase verlängert, woraufhin eine reverse Transkription mit Oligo-dT Primern folgte. Zu diesem Zeitpunkt beinhalteten die Bibliotheken bereits Informationen über den Schneide-Status, die exakte Schnittstelle innerhalb der RNA sowie über die Sequenzen des entsprechenden DNA-Enzyms und der Substrat-RNA. Die Daten, die durch Dz-Seq über die Schneideaktivität der einzelnen Desoxyribozyme erhalten wurden, wurde für einen Teil der Enzyme anhand konventioneller, gel-basierter kinetischer Assays validiert. Diese zeigten eine gute lineare Korrelation (R2 = 0.91). Interessanterweise zeigte Dz-Seq aber nur eine schwache Korrelation zwischen der Schneideaktivität und der Häufigkeit der Desoxyribozyme in der letzten Runde der in vitro Selektion. Zum Beispiel war AM301 nur zu einem geringen Anteil im DZ-seq Datensatz zu finden, war jedoch sehr aktiv. Dies ist nur ein Beispiel des großen Potentials von DZ-seq für die Entdeckung neuer DNA-Enzyme, die für die zukünftige Analyse zahlreicher RNA-Modifikationen angewendet werden könnten. Der zweite Teil dieser Arbeit beschäftigte sich mit der Entwicklung von Ribozymen, die spezifisch eine Ziel-RNA anhängig von deren Struktur markieren können. Die Inspiration hierfür stammt von den kürzlich berichteten Ribozymen FH14 und FJ1. Hierbei handelt es sich um Ribozyme, die über Watson-Crick-Basenpaarung ihre Ziel-RNA erkennen und diese dann sequenz-spezifisch markieren. Unser Ziel war es nun Ribozyme zu entwickeln, die ihre Ziel-RNA über Struktur-spezifische Wechselwirkungen anstelle von Basenpaarung erkennen. Hierbei fokussierten wir uns auf einen RNA G-Quadruplex als entscheidendes Strukturelement. Bei der in vitro Selektion wurde eine RNA Bibliothek verwendet, die kovalent an ein Fragment der 5‘-UTR der BCL2 RNA gebunden war. Von dieser RNA ist bekannt, dass sie einen G-Quadruplex formt. Zwei aufeinanderfolgende Selektionen führten zur Identifikation der Adenylyltransferasen AO10.2 und AR9. Die vorläufige Charakterisierung dieser beiden Ribozyme zeigte, dass AO10.2 die intakte BCL2-Struktur nicht erkennen kann. Stattdessen stellte sich heraus, dass dies das erste trans-aktive Ribozym ist, das effizient Uridin markieren kann, welches sich in einer definierten RNA-Struktur befindet, die mit dem Ribozym hybridisiert ist. Demnach hat es großes Potential als Werkzeug für die spezifische Markierung von RNA eingesetzt werden zu können. Beim zweiten Ribozym AR9 stellte sich heraus, dass es sich um ein trans-aktives, selbst-markierendes RNA-Enzym handelt, welches die gewünschte Reaktion nur bei Vorhandensein der intakten BCL2-Sequenz katalysiert. Basierend auf diesen vorläufigen Ergebnissen könnte AR9 als Reporter-RNA dienen, die sich RNA G-Quadruplexes selbst markiert. Allerdings benötigen sowohl AO10.2 als auch AR9 noch eine detailliertere Charakterisierung, bevor sie für potenzielle Anwendungen eingesetzt werden können. KW - Deoxyribozymes KW - Ribozymes KW - RNA modifications KW - RNA structures KW - RNA G-quadruplex Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-283111 ER - TY - JOUR A1 - Kole, Goutam Kumar A1 - Košćak, Marta A1 - Amar, Anissa A1 - Majhen, Dragomira A1 - Božinović, Ksenija A1 - Brkljaca, Zlatko A1 - Ferger, Matthias A1 - Michail, Evripidis A1 - Lorenzen, Sabine A1 - Friedrich, Alexandra A1 - Krummenacher, Ivo A1 - Moos, Michael A1 - Braunschweig, Holger A1 - Boucekkine, Abdou A1 - Lambert, Christoph A1 - Halet, Jean‐François A1 - Piantanida, Ivo A1 - Müller‐Buschbaum, Klaus A1 - Marder, Todd B. T1 - Methyl Viologens of Bis‐(4’‐Pyridylethynyl)Arenes – Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology JF - Chemistry – A European Journal N2 - A series of bis‐(4’‐pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis‐N‐methylpyridinium compounds were investigated as a class of π‐extended methyl viologens. Their structures were determined by single crystal X‐ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis‐N‐methylpyridinium compound showed a larger two‐photon absorption cross‐section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds‐DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene‐analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi‐faceted features, in combination with its two‐photon absorption properties, suggest it to be a promising lead compound for development of novel light‐activated theranostic agents. KW - cell imaging KW - DNA/RNA binding KW - methyl viologen KW - singlet oxygen KW - two-photon absorption Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287126 VL - 28 IS - 40 ER - TY - JOUR A1 - Rushdi, Mohammed I. A1 - Abdel-Rahman, Iman A. M. A1 - Attia, Eman Zekry A1 - Saber, Hani A1 - Saber, Abdullah A. A1 - Bringmann, Gerhard A1 - Abdelmohsen, Usama Ramadan T1 - The biodiversity of the genus Dictyota: phytochemical and pharmacological natural products prospectives JF - Molecules N2 - Although a broad variety of classes of bioactive compounds have already been isolated from seaweeds of the genus Dictyota, most different species are still chemically and biologically unexplored. Dictyota species are well-known brown seaweeds belonging to the Dictyotaceae (Phaeophyta). The phytochemical composition within the genus Dictyota has recently received considerable interest, and a vast array of components, including diterpenes, sesquiterepenes, sterols, amino acids, as well as saturated and polyunsaturated fatty acids, have been characterized. The contribution of these valued metabolites to the biological potential, which includes anti-proliferative, anti-microbial, antiviral, antioxidant, anti-inflammatory, and anti-hyperpigmentation activities, of the genus Dictyota has also been explored. Therefore, this is the most comprehensive review, focusing on the published literature relevant to the chemically and pharmacologically diverse biopharmaceuticals isolated from different species of the genus Dictyota during the period from 1976 to now. KW - Phaeophyceae KW - Dictyotaceae KW - marine macroalgae KW - brown seaweeds KW - natural products KW - bioactivities KW - Dictyota Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-302428 SN - 1420-3049 VL - 27 IS - 3 ER - TY - JOUR A1 - Dietzsch, Julia A1 - Bialas, David A1 - Bandorf, Johannes A1 - Würthner, Frank A1 - Höbartner, Claudia T1 - Tuning Exciton Coupling of Merocyanine Nucleoside Dimers by RNA, DNA and GNA Double Helix Conformations JF - Angewandte Chemie International Edition N2 - Exciton coupling between two or more chromophores in a specific environment is a key mechanism associated with color tuning and modulation of absorption energies. This concept is well exemplified by natural photosynthetic proteins, and can also be achieved in synthetic nucleic acid nanostructures. Here we report the coupling of barbituric acid merocyanine (BAM) nucleoside analogues and show that exciton coupling can be tuned by the double helix conformation. BAM is a nucleobase mimic that was incorporated in the phosphodiester backbone of RNA, DNA and GNA oligonucleotides. Duplexes with different backbone constitutions and geometries afforded different mutual dye arrangements, leading to distinct optical signatures due to competing modes of chromophore organization via electrostatic, dipolar, - stacking and hydrogen-bonding interactions. The realized supramolecular motifs include hydrogenbonded BAM–adenine base pairs and antiparallel as well as rotationally stacked BAM dimer aggregates with distinct absorption, CD and fluorescence properties. KW - Chromophore Assembly KW - Merocyanine KW - Nucleobase Analogue KW - Supramolecular Element KW - Nucleic Acids Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-254565 ER - TY - JOUR A1 - Ferger, Matthias A1 - Roger, Chantal A1 - Köster, Eva A1 - Rauch, Florian A1 - Lorenzen, Sabine A1 - Krummenacher, Ivo A1 - Friedrich, Alexandra A1 - Košćak, Marta A1 - Nestić, Davor A1 - Braunschweig, Holger A1 - Lambert, Christoph A1 - Piantanida, Ivo A1 - Marder, Todd B. T1 - Electron‐Rich EDOT Linkers in Tetracationic bis‐Triarylborane Chromophores: Influence on Water Stability, Biomacromolecule Sensing, and Photoinduced Cytotoxicity JF - Chemistry – A European Journal N2 - Three novel tetracationic bis‐triarylboranes with 3,4‐ethylenedioxythiophene (EDOT) linkers, and their neutral precursors, showed significant red‐shifted absorption and emission compared to their thiophene‐containing analogues, with one of the EDOT‐derivatives emitting in the NIR region. Only the EDOT‐linked trixylylborane tetracation was stable in aqueous solution, indicating that direct attachment of a thiophene or even 3‐methylthiophene to the boron atom is insufficient to provide hydrolytic stability in aqueous solution. Further comparative analysis of the EDOT‐linked trixylylborane tetracation and its bis‐thiophene analogue revealed efficient photo‐induced singlet oxygen production, with the consequent biological implications. Thus, both analogues bind strongly to ds‐DNA and BSA, very efficiently enter living human cells, accumulate in several different cytoplasmic organelles with no toxic effect but, under intense visible light irradiation, they exhibit almost instantaneous and very strong cytotoxic effects, presumably attributed to singlet oxygen production. Thus, both compounds are intriguing theranostic agents, whose intracellular and probably intra‐tissue location can be monitored by strong fluorescence, allowing switching on of the strong bioactivity by well‐focused visible light. KW - boranes KW - DNA/RNA sensors KW - fluorescent probes KW - singlet oxygen KW - theranostics Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287241 VL - 28 IS - 48 ER - TY - JOUR A1 - Schnitzlein, Matthias A1 - Mützel, Carina A1 - Shoyama, Kazutaka A1 - Farrell, Jeffrey M. A1 - Würthner, Frank T1 - PAHs Containing both Heptagon and Pentagon: Corannulene Extension by [5+2] Annulation JF - European Journal of Organic Chemistry N2 - Utilizing Pd‐catalyzed [5+2] annulation a series of heptagon‐extended corannulenes could be synthesized from a borinic acid precursor furnished by C−H borylation strategy. Single‐crystal X‐ray analysis revealed the presence of two conformational enantiomers crystallizing in a racemic mixture. Through their embedded five‐ and seven‐membered rings these polycyclic aromatic hydrocarbons (PAHs) exhibit both negative and positive curvature and UV/Vis/NIR absorption spectroscopy as well as cyclic voltammetry experiments provided insights into the influence of larger flanking aromatic systems and electron‐donating substituents encompassing the heptagonal ring. Through [5+2] annulation of acenaphthylene an azulene‐containing PAH with intriguing optoelectronical properties including a very small bandgap and absorption over the whole visible spectrum could be obtained. Theoretical calculations were employed to elucidate the long‐wavelength absorption and aromaticity. KW - annulation KW - aromaticity KW - azulene KW - Corannulene KW - polycyclic aromatic hydrocarbons Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-262627 VL - 2022 IS - 5 ER - TY - JOUR A1 - Neitz, Hermann A1 - Bessi, Irene A1 - Kachler, Valentin A1 - Michel, Manuela A1 - Höbartner, Claudia T1 - Tailored tolane‐perfluorotolane assembly as supramolecular base pair replacement in DNA JF - Angewandte Chemie International Edition N2 - Arene‐fluoroarene interactions offer outstanding possibilities for engineering of supramolecular systems, including nucleic acids. Here, we implement the tolane‐perfluorotolane interaction as base pair replacement in DNA. Tolane (THH) and perfluorotolane (TFF) moieties were connected to acyclic backbone units, comprising glycol nucleic acid (GNA) or butyl nucleic acid (BuNA) building blocks, that were incorporated via phosphoramidite chemistry at opposite positions in a DNA duplex. Thermodynamic analyses by UV thermal melting revealed a compelling stabilization by THH/TFF heteropairs only when connected to the BuNA backbone, but not with the shorter GNA linker. Detailed NMR studies confirmed the preference of the BuNA backbone for enhanced polar π‐stacking. This work defines how orthogonal supramolecular interactions can be tailored by small constitutional changes in the DNA backbone, and it inspires future studies of arene‐fluoroarene‐programmed assembly of DNA. KW - arene-fluoroarene KW - artificial base pair KW - DNA KW - sSupramolecular interaction KW - XNA Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312575 VL - 62 IS - 1 ER - TY - JOUR A1 - Schlossarek, Tim A1 - Stepanenko, Vladimir A1 - Beuerle, Florian A1 - Würthner, Frank T1 - Self‐assembled Ru(bda) Coordination Oligomers as Efficient Catalysts for Visible Light‐Driven Water Oxidation in Pure Water JF - Angewandte Chemie International Edition N2 - Water‐soluble multinuclear complexes based on ruthenium 2,2′‐bipyridine‐6,6′‐dicarboxylate (bda) and ditopic bipyridine linker units are investigated in three‐component visible light‐driven water oxidation catalysis. Systematic studies revealed a strong enhancement of the catalytic efficiency in the absence of organic co‐solvents and with increasing oligomer length. In‐depth kinetic and morphological investigations suggest that the enhanced performance is induced by the self‐assembly of linear Ru(bda) oligomers into aggregated superstructures. The obtained turnover frequencies (up to 14.9 s\(^{−1}\)) and turnover numbers (more than 1000) per ruthenium center are the highest reported so far for Ru(bda)‐based photocatalytic water oxidation systems. KW - artificial photosynthesis KW - coordination oligomer KW - photocatalysis KW - Ruthenium complexes KW - water oxidation Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312184 VL - 61 IS - 52 ER - TY - JOUR A1 - Kim, Jin Hong A1 - Schembri, Tim A1 - Bialas, David A1 - Stolte, Matthias A1 - Würthner, Frank T1 - Slip‐Stacked J‐Aggregate Materials for Organic Solar Cells and Photodetectors BT - This paper is dedicated to Prof. Daoben Zhu on the occasion of his 80th birthday JF - Advanced Materials N2 - Dye–dye interactions affect the optical and electronic properties in organic semiconductor films of light harvesting and detecting optoelectronic applications. This review elaborates how to tailor these properties of organic semiconductors for organic solar cells (OSCs) and organic photodiodes (OPDs). While these devices rely on similar materials, the demands for their optical properties are rather different, the former requiring a broad absorption spectrum spanning from the UV over visible up to the near‐infrared region and the latter an ultra‐narrow absorption spectrum at a specific, targeted wavelength. In order to design organic semiconductors satisfying these demands, fundamental insights on the relationship of optical properties are provided depending on molecular packing arrangement and the resultant electronic coupling thereof. Based on recent advancements in the theoretical understanding of intermolecular interactions between slip‐stacked dyes, distinguishing classical J‐aggregates with predominant long‐range Coulomb coupling from charge transfer (CT)‐mediated or ‐coupled J‐aggregates, whose red‐shifts are primarily governed by short‐range orbital interactions, is suggested. Within this framework, the relationship between aggregate structure and functional properties of representative classes of dye aggregates is analyzed for the most advanced OSCs and wavelength‐selective OPDs, providing important insights into the rational design of thin‐film optoelectronic materials. KW - crystal engineering KW - exciton coupling KW - J‐aggregates KW - organic photodiodes KW - organic solar cells Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-276537 VL - 34 IS - 22 ER - TY - THES A1 - Grüne, Marvin T1 - Solid-state NMR Spectroscopic, X-Ray Diffraction and Quantum Chemical Investigations of the Crystalline Cancer Drug Paclitaxel and Paclitaxel incorporated into Polymer Micelles T1 - Festkörper-NMR-, Röntgendiffraktometrie- und quantenchemische Untersuchungen des kristallinen Krebs-Wirkstoffs Paclitaxel und Paclitaxel eingebettet in Polymermizellen N2 - Paclitaxel (PTX) is one of the leading drugs against breast and ovarian cancer. Due to its low solubility, treatment of the patients with this drug requires a very well-suited combination with a soluble pharmaceutical excipient to increase the bioavailability and reduce the strong side ef-fects. One efficient way to achieve this in the future could be the incorporation of PTX into pol-ymeric micelles composed of poly(2-oxazoline) based triblock copolymers (POL) which ena-bles PTX loadings of up to 50 wt.%. However, structural information at an atomic level and thus the knowledge of interaction sites within these promising but complex PTX-POL formula-tions were not yet available. Such results could support the future development of improved excipients for PTX and suitable excipients for other pharmaceutical drugs. Therefore, a solid-state MAS NMR investigation of these amorphous formulations with different POL-PTX com-positions was performed in this thesis as this gives insights of the local structure at an atomic level in its solid state. NMR in solution showed very broad 13C signals of PTX for this system due to the reduced mobility of the incorporated drug which exclude this as an analytical meth-od. In a first study, crystalline PTX was structurally characterized by solid-state NMR as no com-plete 13C spectrum assignment and no 1H NMR data existed for the solid state. In addition, the asymmetric unit of the PTX crystal structure consists of two molecules (Z'=2) that can only be investigated in its solid state. As crystalline PTX in total has about 100 different 13C and 1H chemical shifts with very small differences due to Z’=2, and furthermore, its unit cell consisting of more than 900 atoms, accompanying GIPAW (CASTEP) calculations were required for NMR signal assignments. These calculations were performed using the first three available purely hydrous and anhydrous PTX structures, which were determined by XRD and published by Vel-la-Zarb et al. in 2013. Within this thesis, is was discovered that two investigated batches of commercially available PTX from the same supplier both contained an identical and so far un-known PTX phase that was elucidated by PXRD as well as solid-state NMR data. One of the two batches consists of an additional phase that was shown to be very similar to a known hy-drated phase published in 2013.[1] By heating the batch with the mixture of the two phases un-der vacuum, it is transformed completely to the new dry phase occurring in both PTX batches. Since the drying conditions to obtain anhydrous PTX in-situ on the PXRD setup described by Vella-Zarb et. al.[1] were much softer than ours, we identify our dry phase as a relaxed version of their published anhydrate structure. The PXRD data of the new anhydrate phase was trans-ferred into a new structural model, which currently undergoes geometry optimization. Based on solid-state NMR data at MAS spinning frequencies up to 100 kHz, a 13C and a partial 1H signal assignment for the new anhydrous structure were achieved. These results provided sufficient structural information for further investigations of the micellar POL-PTX system. In a second study, the applicability and benefit of two-dimensional solid-state 14N-1H HMQC MAS NMR spectra for the characterization of amorphous POL-PTX formulations was investi-gated. The mentioned technique has never been applied to a system of similar complexity be-fore and was chosen because around 84% of the small-molecule drugs contain at least one nitrogen atom. In addition, the number of nitrogen atoms in both POL and PTX is much smaller than the number of carbons or hydrogens, which significantly reduces the spectral complexity. 14N has a natural abundance of 99.6% but leads to quadrupolar broadening due to its nuclear spin quantum number I = 1. While this is usually undesirable due to broadening in the resulting 1D 14N NMR spectra, this effect is explicitly used in the 2D 14N-1H HMQC MAS experiment. The indirect 14N measurement can avoid the broadening while maintaining the advantage of the high natural abundance and making use of the much more dispersed signals due to the additional quadrupolar shifts as compared to 15N. This measurement method could be successfully applied to the complex amorphous POL-PTX mixtures. With increasing PTX loading of the formulations, additional peaks arise as spatial proximities of the amide nitrogens of POL to NH or OH groups of PTX. In addition, the 14N quadrupolar shift of these amide nitrogens decreases with increasing PTX content indicating a more symmetric nitrogen environment. The latter can be explained by a transformation of the trigonal planar coordination of the tertiary amide nitrogen atoms in pure POL towards a more tetrahedral environment upon PTX loading induced by the formation of hydrogen bonds with NH/OH groups of PTX. In the third and last project, the results of the two abovementioned studies were used and ex-tended by solid state 13C and two-dimensional 1H-13C as well as 1H-1H MAS NMR data with the aim to derive a structural model of the POL-PTX formulations at an atomic level. The knowledge of the NMR signal assignments for crystalline PTX was transferred to amorphous PTX (present in the micelles of the formulations). The 13C solid-state NMR signals were evalu-ated concerning changes in chemical shifts and full widths of half maximum (FWHM) for the different PTX loadings. In this way, the required information about possible interaction sites at an atomic level becomes available. Due to the complexity of these systems, such proximities often cannot be assigned to special atoms, but more to groups of atoms, as the individual de-velopments of line widths and line shifts are mutually dependent. An advantageous aspect for this analysis was that pure POL already forms unloaded micelles. The evaluation of the data showed that the terminal phenyl groups of PTX seem to be most involved in the interaction by the establishment of the micelle for lowest drug loading and that they are likely to react to the change in the amount of PTX molecules as well. For the incorporation of PTX in the micelles, the following model could be obtained: For lowest drug loading, PTX is mainly located in the inner part of the micelles. Upon further increasing of the loading, it progressively extends to-ward the micellar shell. This could be well shown by the increasing interactions of the hydro-phobic butyl chain of POL and PTX, proceeding in the direction of the polymer backbone with rising drug load. Furthermore, due to the size of PTX and the hydrodynamic radius of the mi-celles, even at the lowest loading, the PTX molecules partially reach the core-shell interface of the micelle. Upon increasing the drug loading, the surface coverage with PTX clusters increas-es based on the obtained model approach. The latter result is supported by DLS and SANS data of this system. The abovementioned results of the 14N-1H HMQC MAS investigation of the POL-PTX formulations support the outlined model. As an outlook, the currently running geometry optimization and subsequently scheduled calcu-lation of the chemical shieldings of the newly obtained anhydrous PTX crystal structure can further improve the solid-state NMR characterization through determination of further spatial proximities among protons using the existing 2D 1H(DQ)-1H(SQ) solid-state MAS NMR spec-trum at 100 kHz rotor spinning frequency. The 2D 14N-1H HMQC MAS NMR experiments were shown to have great potential as a technique for the analysis of other disordered and amor-phous drug delivery systems as well. The results of this thesis should be subsequently applied to other micellar systems with varying pharmaceutical excipients or active ingredients with the goal of systematically achieving higher drug loadings (e.g., for the investigated PTX, the similar drug docetaxel or even different natural products). Additionally, it is planned to transfer the knowledge to another complex polymer system containing poly(amino acids) which offers hy-drogen bonding donor sites for additional intermolecular interactions. Currently, the POL-PTX system is investigated by further SANS studies that may provide another puzzle piece to the model as complementary measurement method in the future. In addition, the use of MD simu-lations might be considered in the future. This would allow a computerized linking of the differ-ent pieces of information with the aim to determine the most likely model. N2 - Paclitaxel (PTX) ist eines der führenden Medikamente gegen Brust-und Eierstockkrebs. Aufgrund seiner geringen Löslichkeit erfordert die Behandlung der Patienten mit diesem Medikament eine sehr gut geeignete Kombination mit einem löslichen pharmazeutischenHilfsstoff, um die Bioverfügbarkeit zu erhöhen und die starken Nebenwirkungen zu reduzieren. Ein effizienter Weg, dies in Zukunft zu erreichen, könnte der Einbau von PTX in polymere Mizellen sein, die aus Poly(2-oxazolin)-basierten Triblock-Copolymeren (POL) bestehen und PTX-Beladungen von bis zu 50 Gew.-% ermöglichen. Strukturelle Informationen auf atomarer Ebene und damit die Kenntnis von Wechselwirkungeninnerhalb dieser vielversprechenden, aber komplexen PTX-POL-Formulierungen waren jedoch bisher nichtverfügbar. Solche Ergebnisse könnten die zukünftige Entwicklung von verbesserten Hilfsstoffen für PTX und von geeigneten Hilfsstoffen für andere pharmazeutische Wirkstoffe unterstützen. Aus diesem Grund wurdenin der vorliegenden DissertationFestkörper-NMR-Untersuchungen andiesenamorphen Formulierungen mit unterschiedlichen POL-PTX Zusammensetzungen durchgeführt, weil damit Einblickein die lokale Struktur auf atomarer Ebene im festen Zustand erhalten werden können. Aufgrund der verringerten Mobilität des eingebrachten Wirkstoffs in diesem System ergeben NMR-Messungen in Lösung sehr breite 13C-PTX-Signale, was diese Technikals Analysemethode ausschließt. ... KW - Wirkstoff-Träger-System KW - NMR-Spektroskopie KW - Röntgendiffraktometrie KW - Taxol KW - Quantenchemie KW - Solid-State NMR Spectroscopy KW - X-Ray Diffraction KW - Quantum Chemical Calculations KW - Drug Delivery System KW - Taxol KW - Festkörper-NMR KW - quantenchemische Berechnungen Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-237199 ER - TY - CHAP A1 - Liaqat, Anam A1 - Sednev, Maksim V. A1 - Höbartner, Claudia T1 - In Vitro Selection of Deoxyribozymes for the Detection of RNA Modifications T2 - Ribosome Biogenesis: Methods and Protocols N2 - Deoxyribozymes are artificially evolved DNA molecules with catalytic abilities. RNA-cleaving deoxyribozymes have been recognized as an efficient tool for detection of modifications in target RNAs and provide an alternative to traditional and modern methods for detection of ribose or nucleobase methylation. However, there are only few examples of DNA enzymes that specifically reveal the presence of a certain type of modification, including N6-methyladenosine, and the knowledge about how DNA enzymes recognize modified RNAs is still extremely limited. Therefore, DNA enzymes cannot be easily engineered for the analysis of desired RNA modifications, but are instead identified by in vitro selection from random DNA libraries using synthetic modified RNA substrates. This protocol describes a general in vitro selection stagtegy to evolve new RNA-cleaving DNA enzymes that can efficiently differentiate modified RNA substrates from their unmodified counterpart. KW - RNA KW - deoxyribozymes KW - modified RNA nucleotides KW - catalytic DNA KW - epitranscriptomics KW - in vitro selection KW - RNA cleavage Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-279208 SN - 978-1-0716-2501-9 PB - Humana Press ER - TY - JOUR A1 - Feng, Yi A1 - Zhou, Jiadong A1 - Qiu, Honglin A1 - Schnitzlein, Matthias A1 - Hu, Jingtao A1 - Liu, Linlin A1 - Würthner, Frank A1 - Xie, Zengqi T1 - Boron‐Locked Starazine – A Soluble and Fluorescent Analogue of Starphene JF - Chemistry – A European Journal N2 - A starlike heterocyclic molecule containing an electron‐deficient nonaaza‐core structure and three peripheral isoquinolines locked by three tetracoordinate borons, namely isoquinoline‐nona‐starazine (QNSA), is synthesized by using readily available reactants through a rather straightforward approach. This new heteroatom‐rich QNSA possesses a quasi‐planar π‐backbone structure, and bears phenyl substituents on borons which protrude on both sides of the π‐backbones endowing it with good solubility in common organic solvents. Contrasting to its starphene analogue, QNSA shows intense fluorescence with a quantum yield (PLQY) of up to 62 % in dilute solution. KW - conjugated molecule KW - electronic structure KW - luminescence KW - starazine KW - starphene analogue Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-276423 VL - 28 IS - 29 ER - TY - THES A1 - Muzha, Andreas T1 - Herstellung und Charakterisierung kolloidaler Lösungen diamantbasierter und verwandter Materialien T1 - Preparation and characterization of colloidal solutions of diamond-based and related materials N2 - In der vorliegenden Publikation wurden stabile kolloidale Lösungen aus CVD-Diamant, Detonationsdiamant sowie artverwandten Materialien hergestellt und charakterisiert Besonderes Augenmerk wurde bei der Zerkleinerung von CVD Diamant daraufgelegt, dass die nanoskaligen Partikel ihre materialspezifischen Eigenschaften auch bei Reduktion der Größe beibehalten. Systematisch wurde die Zerkleinerung in einer Planetenmühle analysiert. Es wurde sowohl die minimal erreichbare Partikelgröße, als auch die Menge an erzeugtem, nanoskaligem Material bewertet. Um die Vermahlung zu verbessern, wurden die Geschwindigkeit der Mühle, die Größe der Mahlkörper, die Dauer der Vermahlung, sowie die eingesetzten Lösemittel variiert. Des Weiteren konnten durch die Vermahlung unterschiedlich hergestellter CVD Diamantfilme in einer Vibrationsmühle die Einflüsse von Schichtdicke und Korngröße der Diamantkristalle untersucht werden. Durch Bearbeitung von Detonationsdiamanten und Kohlenstoffnanozwiebeln wurden stabile kolloidale Lösungen hergestellt, mit Partikelgrößen im unteren Nanometerbereich. Diese sind im alkalischen pH-Bereich stabil sein, hierfür wurde durch Luft und Säureoxidation oxidierter Detonationsdiamant und oxidierte Kohlenstoffnanozwiebeln hergestellt. Mithilfe der thermogravimetrischen Analyse und Infrarotspektroskopie wurde die hierfür optimale Temperatur und Dauer bestimmt. N2 - In the present publication, stable colloidal solutions of CVD diamond, detonation diamond and related materials were produced and characterized. During the grinding of CVD diamond, special attention was paid to ensuring that the nanoscale particles retain their material-specific properties even when their size is reduced. The grinding in a planetary mill was analyzed systematically. Both the minimum achievable particle size and the amount of nanoscale material produced were evaluated. In order to improve the grinding, the speed of the mill, the size of the grinding media, the duration of the grinding and the solvents used were varied. Furthermore, the influences of layer thickness and grain size of the diamond crystals could be investigated by grinding differently produced CVD diamond films in a vibration mill. Stable colloidal solutions were prepared from detonation diamonds and carbon nano onions, with particle sizes in the sub-nanometer range. These are stable in alkaline pH range. For this purpose oxidized detonation diamond and oxidized carbon nano onions were modified by air and acid oxidation. The optimum temperature and duration for this was determined with the aid of thermogravimetric analysis and infrared spectroscopy. KW - Diamant KW - Kolloid / Lösung KW - Detonationsdiamant KW - CVD-Diamant KW - Kohlenstoffnanozwiebel Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-296685 ER - TY - THES A1 - Selby, Joshua T1 - Design and Chiroptical Properties of Chirally Substituted Indolenine Squaraine Mono-, Oligo-, and Polymers T1 - Design und chiroptische Eigenschaften von chiral substituierten Indolenin-Squarain-Mono-, Oligo- und Polymeren N2 - A series of monomeric chirally substituted indolenine squaraine monomers were successfully synthesized and utilized for the construction of various oligo- and polymers, in order to study their chiroptical properties in terms of exciton chirality. The quaternary carbon atom at the 3-position of the indolenine subunit, as well as the alkyl side chain attached to the indolenine nitrogen were selected as the most suitable site for chiral functionalization. For the C(3)-chiral derivatives, two synthetic routes depending on the desired substitution at the stereogenic center were established. The chiral side chains were prepared via Evans asymmetric alkylation where the resulting branching point at the 2 position constituted the chiral center. While the chiral substitution only had minor effects on the linear optical properties and geometric structure of the chromophore, all compounds exhibited a distinct and measurable CD signal that correlated with the distance of the chiral center to the central chromophore. Polymers bearing chiral side chains exhibited a solvent- and temperature-dependent helix-coil equilibrium, which was influenced by the type of side chain used. CD spectroscopy revealed the helical conformation to possess a preferred twist sense, and temperature-dependent measurements showed the degree of homohelicity to be nearly complete in certain cases. Furthermore, a CPL signal was able to be obtained for the helical conformer of one polymer. Various (co)oligo- and polymers comprising the C(3)-chiral monomers only displayed a solvent-independent J-type absorption behavior and thus did not form helical conformations in solution. CD spectroscopy revealed a solvent-dependent adoption of quasi-enantiomeric conformers, which was elucidated by quantum chemical TDDFT calculations. N2 - Eine Reihe von monomeren, chiral substituierten Indolenin-Squarain-Monomeren wurde erfolgreich synthetisiert und für die Konstruktion verschiedener Oligo- und Polymere verwendet, um ihre chiroptischen Eigenschaften in Bezug auf die Exzitonenchiralität zu untersuchen. Als geeignete Stelle für die chirale Funktionalisierung wurden das quartäre Kohlenstoffatom an der 3-Position der Indolenineinheit sowie die an den Indolenin- Stickstoff gebundene Alkylseitenkette ausgewählt. Für die C(3)-chiralen Derivate wurden je nach gewünschter Substitution am stereogenen Zentrum zwei Synthesrouten etabliert. Die chiralen Seitenketten wurden über eine asymmetrische Evans-Alkylierung synthetisiert, wobei der resultierende Verzweigungspunkt an der 2-Position das chirale Zentrum darstellte. Während die chirale Substitution nur geringe Auswirkungen auf die linearen optischen Eigenschaften und die geometrische Struktur des Chromophors hatte, zeigten alle Verbindungen ein deutliches und messbares CD-Signal, das mit dem Abstand des chiralen Zentrums zum zentralen Chromophor korrelierte. Polymere mit chiralen Seitenketten zeigten ein lösungsmittel- und temperaturabhängiges Helix-Knäuel-Gleichgewicht, das durch die Art der verwendeten Seitenkette beeinflusst wurde. Durch CD Spektroskopie konnte gezeigt werden, dass die helikale Konformation einen bevorzugten Drehsinn besitzt. Temperaturabhängige CD Messungen zeigten, dass der Grad der Homohelizität in bestimmten Fällen nahezu vollständig ist. Weiterhin konnte für das helikale Konformer eines Polymers ein CPL-Signal erhalten werden. Verschiedene (Co)oligo- und Polymere bestehend aus den C(3)-chiralen Monomere zeigten nur ein lösungsmittelunabhängiges J- Typ Absorptionsverhalten und bildeten daher in Lösung keine helikalen Konformationen. CD-Spektroskopie zeigte eine lösungsmittelabhängige Annahme von quasi-enantiomeren Konformationen, was durch quantenchemische TDDFT-Rechnungen aufgeklärt wurde. KW - Squaraine KW - Oligomere KW - Polymere KW - Chiralität KW - Chemische Synthese KW - Asymmetrische Synthese KW - CD-Spektroskopie KW - Helix-Knäuel-Umwandlung KW - J- and H-Aggregate KW - Asymmetric synthesis KW - Helix-Coil-Transition KW - J- and H-Aggregates KW - Circular dichroism Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-282067 ER - TY - THES A1 - Merz, Viktor T1 - Funktionalisierung und Untersuchung von Nanodiamanten für biomedizinische und sensorische Anwendungen T1 - Functionalization and Investigation of Nanodiamonds for Biomedical and Sensor Applications N2 - Nanodiamant (ND) ist ein vielseitiges und vielversprechendes Material für Bio-Anwendungen. Trotz vieler Bemühungen bleibt die Agglomeration von Nanodiamant und die unspezifische Adsorption von Proteinen an der ND-Oberfläche bei Kontakt mit Bioflüssigkeiten ein großes Hindernis für biomedizinische Anwendungen. Eine Auswahl verzweigter und linearer Moleküle mit überlegener Fähigkeit zur kolloidalen Stabilisierung von Nanopartikeln in Salz- und Zellmedienumgebung, für bis zu 30 Tage, wurde an die ND-Oberfläche angebracht. Das Baukastensystem mit Azid als Außengruppen bietet eine große Vielfalt an Bindungen mit vielen Molekülen, wie z. B. Medikamenten, Farbstoffen oder Targeting-Molekülen. Das Anhängen von z. B. Zwitterionen an die Kette schützt die ND-Oberfläche vor der Bildung einer Proteinkorona, wenn die Partikel mit proteinhaltigen Bioflüssigkeiten in Kontakt kommen. Die Ergebnisse der thermogravimetrischen Analyse der Beladung der ND-Oberfläche zeigen eine signifikante Verhinderung der Proteinadsorption von bis zu 98 % im Vergleich zu NDs ohne zwitterionische Kopfgruppen und eine lange kolloidale Stabilität, wenn Tetraethylenglykol (TEG) an die Oberfläche gebunden wird. Die Vielseitigkeit des modularen Systems, um nicht nur zwitterionische Ketten, sondern auch klickbare funktionelle Moleküle an fluoreszierende Nanodiamanten (fNDs) zu binden, zeigt das Potenzial des Systems am Nanodiamanten. Unter Verwendung von Defektstrukturen, wie Stickstoff-Vakanz-Zentren (NV), können Diamantpartikel aufgrund ihres weitgehend ungiftigen Verhaltens als fluoreszierende Nanodiamanten (fNDs) für photostabile Markierung, Bioimaging und nanoskalige Sensorik in lebenden Zellen und Organismen verwendet werden. Um die fND-Oberfläche zu funktionalisieren, wurde eine neuartige Mahltechnik mit Diazoniumsalzen etabliert, um ein Pfropfen auf wenig reaktive HPHT-fNDs durchzuführen, was zu einer hohen Oberflächenbeladung und einem hohen negativen Zetapotenzial führt. Die Kombination der Vorteile von TEG und zwitterionhaltigen Gruppen mit der Fähigkeit zum Targeting von Antikörpern auf fND bestätigt zum ersten Mal die verbesserte kolloidale Stabilität in Experimenten mit lebenden Zellen. Darüber hinaus deuten die Ergebnisse auf eine verbesserte Corona-Abstoßung im Vergleich zu fND ohne zwitterionhaltige Kopfgruppen hin. Infolgedessen wurden die Zirkulationszeiten von 4 (fND ohne Zwitterionenkette, aber mit Antikörper) auf 17 (mit Antikörper und Zwitterionenketten) Stunden vergrößert. In nicht-biomedizinischen Anwendungen kann das modulare System als Sonde für Schwermetalle durch die Anbindung von Farbstoffen verwendet werden. Die Detektion von Metallen in verschiedenen Umgebungen mit hoher Selektivität und Spezifität ist eine der Voraussetzungen für den Kampf gegen die Umweltverschmutzung mit diesen Elementen. Pyrene sind gut geeignet und weit bekannt für die Fluoreszenzsensorik in verschiedenen Medien. Das angewandte Sensorprinzip beruht typischerweise auf der Bildung von intra- und intermolekularen Excimeren, was jedoch den Empfindlichkeitsbereich aufgrund der Maskierung von z.B. Quenching-Effekten durch die Excimer-Emission einschränkt. Diese Studie zeigt einen hochselektiven, strukturstabilen chemischen Sensor, der auf der monomeren Fluoreszenz von Pyrenanteilen mit Triazolgruppen basiert. Dieser Sensor kann Cu2+, Pb2+ und Hg2+ in organischen Lösungsmitteln über einen weiten Konzentrationsbereich quantitativ nachweisen, auch in Gegenwart von ubiquitären Ionen wie Na+, K+, Ca2+ und Mg2+. Die stark emittierende Fluoreszenz des Sensors mit einer langen Lebensdauer von 165 ns wird durch eine 1:1-Komplexbildung bei Zugabe von Metallionen in Acetonitril gelöscht. Bei Zugabe eines zehnfachen Überschusses des Metallions zum Sensor bilden sich Agglomerate mit einem Durchmesser von etwa 3 nm. Aufgrund der komplexen Wechselwirkungen im System werden konventionelle lineare Korrelationen nicht für alle Konzentrationen beobachtet. Daher wird ein kritischer Vergleich zwischen der konventionellen Job-Plot-Interpretation, der Methode von Benesi-Hildebrand und einem nicht-linearen Fit vorgestellt. Das vorgestellte System ermöglicht die spezifische und robuste Erfassung von medizinisch und ökologisch relevanten Ionen im gesundheitsrelevanten nM-Bereich und könnte z. B. zur Überwachung der entsprechenden Ionen in Abfallströmen eingesetzt werden. Doch häufig landen diese Abfallströme in empfindlichen Aquakulturen, wo eine solche Sensortechnik nur funktioniert, wenn die Sonde wasserlöslich ist, um die Ausbreitung und Bildung von Umweltschäden durch Schwermetalle zu überwachen. Viele Chemosensoren arbeiten nur in bestimmten Lösungsmitteln und unter hochreinen Bedingungen quantitativ. In dieser Arbeit wird eine Methode zur Stabilisierung von wasserunlöslichen Chemosensoren auf Nanodiamanten in salzhaltigem Wasser unter Beibehaltung der Sensoreffektivität und -spezifität sowie der kolloidalen Stabilität vorgestellt. Zusätzlich wird die Sensorfähigkeit in organischen Lösungsmitteln beibehalten. Diese Studie gibt Einblick in die Absorptionsfähigkeit von Pyren-Derivaten an der Nanodiamant-Oberfläche und einen Weg, diese reversibel zu desorbieren. Außerdem beweist das System, dass in Anwesenheit von 95 % Sauerstoffatmosphäre bei der Fluoreszenzmessung die Ergebnisse nicht von denen in Argonatmosphäre abweichen. Darüber hinaus stört das Vorhandensein gängiger Ionen im Wasser die kolloidale Stabilität der NDs nicht und hat auch keinen Einfluss auf die Sensorfunktionalität und ist somit ein vielversprechender Kandidat für Messungen ohne aufwändige Präparationsschritte. N2 - Nanodiamond (ND) is a versatile and promising material for bio-applications. Despite many efforts, agglomeration of nanodiamond and the non-specific adsorption of proteins on the ND surface when exposed to bio-fluids remains a major obstacle for biomedical applications. An assortment of branched and linear molecules with superior ability to colloidally stabilize nanoparticles in salt and cell media environment, for up to 30 days, was attached to the ND’s surface. The building box system with azide as external groups offers a huge variety of binding with many molecules, such as drugs, dyes or targeting molecules, is possible. Clicking, for instance, zwitterions moieties to the chain protects ND surface from protein corona forming when the particles get in contact with biofluids containing proteins. Thermogravimetric analysis results of the ND surface loading show a significant prevention of up to 98 % of the protein adsorption compared with NDs without zwitterionic headgroups and long colloidal stability when tetraethylene glycol (TEG) are attached to the surface. The versatility of the modular system to bind not only zwitterionic chains but also clickable functional molecules to fluorescent nanodiamonds (fNDs) demonstrates the potential of the system at the nanodiamond. Using defect structures, such as nitrogen-vacancy (NV) centers, diamond particles, due to their widely non-toxic behavior, can be used as fNDs for photostable labeling, bioimaging and nanoscale sensing in living cells and organisms. To functionalize the fND surface a novel milling technique with diazonium salts was established to perform grafting on poorly reactive HPHT fNDs yielding in high surface loading and high negative zeta potential. Combining the benefits of TEG and zwitterion containing groups with antibody enabled nucleus targeting ability on fND confirms the enhanced colloidal stability in living cells experiments for the first time. Furthermore, the results indicate an improved corona repulsion compared with fND without zwitterion containing headgroups. As a result, the circulation times were enlarged from 4 (fND without zwitterion chain but with antibody) to 17 (with antibody and zwitterion chains) hours. In non-biomedical applications, the modular system can be used as a probe for heavy metals by binding it to dyes. Detection of metals in different environments with high selectivity and specificity is one of the prerequisites of the fight against environmental pollution with these elements. Pyrenes are well suited and known for fluorescence sensing in different media. The applied sensing principle typically relies on the formation of intra- and intermolecular excimers, which is however limiting the sensitivity range due to masking of e.g. quenching effects by the excimer emission. This study shows a highly selective, structurally rigid chemical sensor based on the monomer fluorescence of pyrene moieties bearing triazole groups. This probe can quantitatively detect Cu2+, Pb2+ and Hg2+ in organic solvents over a broad concentration range, even in the presence of ubiquitous ions such as Na+, K+, Ca2+ and Mg2+. The strongly emissive sensor’s fluorescence with a long lifetime of 165 ns is quenched by a 1:1 complex formation upon addition of metal ions in acetonitrile. Upon addition of a tenfold excess of the metal ion to the sensor, agglomerates with a diameter of about 3 nm are formed. Due to complex interactions in the system, conventional linear correlations are not observed for all concentrations. Therefore, a critical comparison between the conventional Job plot interpretation, the method of Benesi-Hildebrand, and a non-linear fit is presented. The reported system enables the specific and robust sensing of medically and environmentally relevant ions in the health-relevant nM range and could be used e.g. for the monitoring of the respective ions in waste streams. Nonetheless, often these waste streams end up in sensitive aquacultures, where such sensor technology only works if the probe is water-soluble to monitor the spread and formation of environmental damage from heavy metals. Many chemosensors only work quantitatively in specific solvents and under highly pure conditions. In this thesis a method to stabilize water-insoluble chemosensors on nanodiamonds in saline water while maintaining the sensor efficacy and specificityas as well as colloidal stability is presented. Additionally, the sensor capability is retained in organic solvents. This study provides insight into the absorptivity of pyrene derivatives to the nanodiamond surface and a way to reversibly desorb them. Moreover, the system proves that in presence of 95 % oxygen atmosphere while the fluoresce measurement the results of the do not vary from the one in argon atmosphere. Furthermore, the presence of common ions in water do not disturb the colloidal stability of the NDs and also no influence the sensor functionality and thus is highly promising candidate for measurement without cumbersome preparation steps. KW - Chemosensor KW - Nanodiamant KW - Kolloidalstabilität KW - Protein Corona KW - Targeting Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-245888 ER - TY - JOUR A1 - Schnitzlein, Matthias A1 - Zhu, Chongwei A1 - Shoyama, Kazutaka A1 - Würthner, Frank T1 - π‐Extended Pleiadienes by [5+2] Annulation of 1‐Boraphenalenes and ortho‐Dihaloarenes JF - Chemistry – A European Journal N2 - Palladium‐catalyzed [5+2] annulation of 1‐boraphenalenes with ortho‐dihaloarenes afforded negatively curved π‐extended pleiadienes. Two benzo[1,2‐i:4,5‐i’]dipleiadienes (BDPs) featuring a seven‐six‐seven‐membered ring arrangement were synthesized and investigated. Their crystal structure revealed a unique packing arrangement and theoretical calculations were employed to shed light onto the dynamic behavior of the BDP moiety and its aromaticity. Further, a naphthalene‐fused pleiadiene was stitched together by oxidative cyclodehydrogenation to yield an additional five‐membered ring. This formal azulene moiety led to distinct changes in optical and redox properties and increased perturbation of the aromatic system. KW - annulation KW - aromaticity KW - azulene KW - cyclodehydrogenation KW - polycyclic aromatic hydrocarbons Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293919 VL - 28 IS - 61 ER - TY - JOUR A1 - Sun, Meng‐Jia A1 - Anhalt, Olga A1 - Sárosi, Menyhárt B. A1 - Stolte, Matthias A1 - Würthner, Frank T1 - Activating Organic Phosphorescence via Heavy Metal–π Interaction Induced Intersystem Crossing JF - Advanced Materials N2 - Heavy‐atom‐containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface‐bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid‐state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)\(_{2}\)) as a triplet sensitizer and electron‐deficient 1,4,5,8‐naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room‐temperature phosphorescence confined in the low‐lying, long‐lived triplet state of NDIs with photoluminescence (PL) quantum yield (Φ\(_{PL}\)) exceeding 25% and a phosphorescence lifetime (τ\(_{Ph}\)) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin–orbital coupling between the constituents. KW - cocrystallization KW - naphthalene diimide KW - phosphorescence KW - platinum complexes KW - triplet sensitization Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312248 VL - 34 IS - 51 ER - TY - JOUR A1 - Bold, Kevin A1 - Stolte, Matthias A1 - Shoyama, Kazutaka A1 - Holzapfel, Marco A1 - Schmiedel, Alexander A1 - Lambert, Christoph A1 - Würthner, Frank T1 - Macrocyclic donor-acceptor dyads composed of a perylene bisimide dye surrounded by oligothiophene bridges JF - Angewandte Chemie Internationale Edition N2 - Two macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) dye have been synthesized via a platinum-mediated cross-coupling strategy. The crystal structure of the double bridged PBI reveals all syn-arranged thiophene units that completely enclose the planar PBI chromophore via a 12-membered macrocycle. The target structures were characterized by steady-state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor–acceptor dyads show ultrafast Förster Resonance Energy Transfer and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent. KW - organic chemistry KW - photoinduced electron transfer KW - donor–acceptor dyads KW - macrocycles KW - oligothiophenes KW - perylenebisimide Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256569 VL - 61 IS - 1 ER - TY - JOUR A1 - Karak, Suvendu A1 - Stepanenko, Vladimir A1 - Addicoat, Matthew A. A1 - Keßler, Philipp A1 - Moser, Simon A1 - Beuerle, Florian A1 - Würthner, Frank T1 - A Covalent Organic Framework for Cooperative Water Oxidation JF - Journal of the American Chemical Society N2 - The future of water-derived hydrogen as the “sustainable energy source” straightaway bets on the success of the sluggish oxygen-generating half-reaction. The endeavor to emulate the natural photosystem II for efficient water oxidation has been extended across the spectrum of organic and inorganic combinations. However, the achievement has so far been restricted to homogeneous catalysts rather than their pristine heterogeneous forms. The poor structural understanding and control over the mechanistic pathway often impede the overall development. Herein, we have synthesized a highly crystalline covalent organic framework (COF) for chemical and photochemical water oxidation. The interpenetrated structure assures the catalyst stability, as the catalyst’s performance remains unaltered after several cycles. This COF exhibits the highest ever accomplished catalytic activity for such an organometallic crystalline solid-state material where the rate of oxygen evolution is as high as ∼26,000 μmol L\(^{–1}\) s\(^{–1}\) (second-order rate constant k ≈ 1650 μmol L s\(^{–1}\) g\(^{–2}\)). The catalyst also proves its exceptional activity (k ≈ 1600 μmol L s\(^{–1}\) g\(^{–2}\)) during light-driven water oxidation under very dilute conditions. The cooperative interaction between metal centers in the crystalline network offers 20–30-fold superior activity during chemical as well as photocatalytic water oxidation as compared to its amorphous polymeric counterpart. KW - water oxidation KW - sustainable energy source KW - covalent organic framework KW - catalyst KW - crystalline KW - catalysis KW - nanoparticles Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287591 UR - https://pubs.acs.org/doi/10.1021/jacs.2c07282 SN - 0002-7863 VL - 144 IS - 38 ER - TY - JOUR A1 - Bold, Kevin A1 - Stolte, Matthias A1 - Shoyama, Kazutaka A1 - Krause, Ana‐Maria A1 - Schmiedel, Alexander A1 - Holzapfel, Marco A1 - Lambert, Christoph A1 - Würthner, Frank T1 - Macrocyclic Donor‐Acceptor Dyads Composed of Oligothiophene Half‐Cycles and Perylene Bisimides JF - Chemistry – A European Journal N2 - A series of donor‐acceptor (D−A) macrocyclic dyads consisting of an electron‐poor perylene bisimide (PBI) π‐scaffold bridged with electron‐rich α‐oligothiophenes bearing four, five, six and seven thiophene units between the two phenyl‐imide substituents has been synthesized and characterized by steady‐state UV/Vis absorption and fluorescence spectroscopy, cyclic and differential pulse voltammetry as well as transient absorption spectroscopy. Tying the oligothiophene strands in a conformationally fixed macrocyclic arrangement leads to a more rigid π‐scaffold with vibronic fine structure in the respective absorption spectra. Electrochemical analysis disclosed charged state properties in solution which are strongly dependent on the degree of rigidification within the individual macrocycle. Investigation of the excited state dynamics revealed an oligothiophene bridge size‐dependent fast charge transfer process for the macrocyclic dyads upon PBI subunit excitation. KW - donor-acceptor dyad KW - macrocycle KW - oligothiophene KW - perylene bisimide KW - photoinduced electron transfer Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-276435 VL - 28 IS - 30 ER - TY - JOUR A1 - Eder, Sascha A1 - Hollmann, Claudia A1 - Mandasari, Putri A1 - Wittmann, Pia A1 - Schumacher, Fabian A1 - Kleuser, Burkhard A1 - Fink, Julian A1 - Seibel, Jürgen A1 - Schneider-Schaulies, Jürgen A1 - Stigloher, Christian A1 - Beyersdorf, Niklas A1 - Dembski, Sofia T1 - Synthesis and characterization of ceramide-containing liposomes as membrane models for different T cell subpopulations JF - Journal of Functional Biomaterials N2 - A fine balance of regulatory (T\(_{reg}\)) and conventional CD4\(^+\) T cells (T\(_{conv}\)) is required to prevent harmful immune responses, while at the same time ensuring the development of protective immunity against pathogens. As for many cellular processes, sphingolipid metabolism also crucially modulates the T\(_{reg}\)/T\(_{conv}\) balance. However, our understanding of how sphingolipid metabolism is involved in T cell biology is still evolving and a better characterization of the tools at hand is required to advance the field. Therefore, we established a reductionist liposomal membrane model system to imitate the plasma membrane of mouse T\(_{reg}\) and T\(_{conv}\) with regards to their ceramide content. We found that the capacity of membranes to incorporate externally added azide-functionalized ceramide positively correlated with the ceramide content of the liposomes. Moreover, we studied the impact of the different liposomal preparations on primary mouse splenocytes in vitro. The addition of liposomes to resting, but not activated, splenocytes maintained viability with liposomes containing high amounts of C\(_{16}\)-ceramide being most efficient. Our data thus suggest that differences in ceramide post-incorporation into T\(_{reg}\) and T\(_{conv}\) reflect differences in the ceramide content of cellular membranes. KW - liposome KW - ceramide KW - cell membrane model Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286130 SN - 2079-4983 VL - 13 IS - 3 ER - TY - JOUR A1 - Wildervanck, Martijn J. A1 - Hecht, Reinhard A1 - Nowak-Król, Agnieszka T1 - Synthesis and strong solvatochromism of push-pull thienylthiazole boron complexes JF - Molecules N2 - The solvatochromic behavior of two donor-π bridge-acceptor (D-π-A) compounds based on the 2-(3-boryl-2-thienyl)thiazole π-linker and indandione acceptor moiety are investigated. DFT/TD-DFT calculations were performed in combination with steady-state absorption and emission measurements, along with electrochemical studies, to elucidate the effect of two different strongly electron-donating hydrazonyl units on the solvatochromic and fluorescence behavior of these compounds. The Lippert–Mataga equation was used to estimate the change in dipole moments (Δµ) between ground and excited states based on the measured spectroscopic properties in solvents of varying polarity with the data being supported by theoretical studies. The two asymmetrical D-π-A molecules feature strong solvatochromic shifts in fluorescence of up to ~4300 cm\(^{−1}\) and a concomitant change of the emission color from yellow to red. These changes were accompanied by an increase in Stokes shift to reach values as large as ~5700–5800 cm\(^{−1}\). Quantum yields of ca. 0.75 could be observed for the N,N-dimethylhydrazonyl derivative in nonpolar solvents, which gradually decreased along with increasing solvent polarity, as opposed to the consistently reduced values obtained for the N,N-diphenylhydrazonyl derivative of up to ca. 0.20 in nonpolar solvents. These two push–pull molecules are contrasted with a structurally similar acceptor-π bridge-acceptor (A-π-A) compound. KW - solvatochromism KW - donor–acceptor KW - fluorescence KW - hydrazone KW - Lippert–Mataga plot KW - push–pull thienylthiazole KW - tetracoordinated boron Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286186 SN - 1420-3049 VL - 27 IS - 17 ER - TY - JOUR A1 - Geiger, Nina A1 - Kersting, Louise A1 - Schlegel, Jan A1 - Stelz, Linda A1 - Fähr, Sofie A1 - Diesendorf, Viktoria A1 - Roll, Valeria A1 - Sostmann, Marie A1 - König, Eva-Maria A1 - Reinhard, Sebastian A1 - Brenner, Daniela A1 - Schneider-Schaulies, Sibylle A1 - Sauer, Markus A1 - Seibel, Jürgen A1 - Bodem, Jochen T1 - The acid ceramidase is a SARS-CoV-2 host factor JF - Cells N2 - SARS-CoV-2 variants such as the delta or omicron variants, with higher transmission rates, accelerated the global COVID-19 pandemic. Thus, novel therapeutic strategies need to be deployed. The inhibition of acid sphingomyelinase (ASM), interfering with viral entry by fluoxetine was reported. Here, we described the acid ceramidase as an additional target of fluoxetine. To discover these effects, we synthesized an ASM-independent fluoxetine derivative, AKS466. High-resolution SARS-CoV-2–RNA FISH and RTqPCR analyses demonstrate that AKS466 down-regulates viral gene expression. It is shown that SARS-CoV-2 deacidifies the lysosomal pH using the ORF3 protein. However, treatment with AKS488 or fluoxetine lowers the lysosomal pH. Our biochemical results show that AKS466 localizes to the endo-lysosomal replication compartments of infected cells, and demonstrate the enrichment of the viral genomic, minus-stranded RNA and mRNAs there. Both fluoxetine and AKS466 inhibit the acid ceramidase activity, cause endo-lysosomal ceramide elevation, and interfere with viral replication. Furthermore, Ceranib-2, a specific acid ceramidase inhibitor, reduces SARS-CoV-2 replication and, most importantly, the exogenous supplementation of C6-ceramide interferes with viral replication. These results support the hypotheses that the acid ceramidase is a SARS-CoV-2 host factor. KW - SARS-CoV-2 KW - ceramides KW - ceramidase KW - fluoxetine KW - acid sphingomyelinase Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286105 SN - 2073-4409 VL - 11 IS - 16 ER -