@article{SchreckChristl1987, author = {Schreck, Michael and Christl, Manfred}, title = {Generation and Interception of 1-Oxa-3,4-cyclohexadiene}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31601}, year = {1987}, abstract = {No abstract available}, subject = {Chemie}, language = {en} } @phdthesis{Schreck2018, author = {Schreck, Maximilian}, title = {Synthesis and Photophysics of Linear and Star-Shaped Oligomers of Squaraine Dyes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-174272}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2018}, abstract = {In this thesis, the synthesis and photophysics of a great variety of squaraine dyes are presented. This variety is based on four parent squaraines containing either indolenine or quinoline heterocycles. By a suitable choice of the donor and acceptor unit, the optical properties can already be adapted to the properties desired on the stage of the monomer. To promote a further derivatisation of these dyes, diverse functional groups are attached to the monomers using transition metal-catalysed C-C coupling reactions. However, this has to be preceded by the synthesis of bromine-functionalised derivatives as a direct halogenation of squaraine dyes is not feasible. Therefore, the halogen function is already introduced in precursor molecules giving rise to a molecular building block system containing bromine-, boronic ester-, and alkyne-functionalised monomer units, which pave the way to a plethora of squaraine oligomers and polymers. The indolenine homopolymer pSQB-1 as well as the corresponding small molecular weight oligomers dSQB-1 and tSQB were synthesized applying Ni-mediated Yamamoto and Pd-catalysed Suzuki coupling methodologies, respectively. The motivation for this project relied on the fundamental investigations by V{\"o}lker et al. on pSQB-V. A progressive red-shift of the lowest energy absorption maximum from the dimer to the polymer was observed in CHCl3 compared to the monomer. With increasing number of monomer units, the exciton coupling decreases from the dimer to the polymer. In addition, the shape of the absorption band manifold shows a strong dependence on the solvent, which was also observed by V{\"o}lker et al. J-type aggregate behavior is found in chlorinated solvents such as CHCl3 and DCM, whereas H-type aggregates are formed in acetone. Temperature-dependent absorption studies in PhCN reveals a reversible equilibrium of diverse polymer conformers, which manifests itself in a gradual change from H-aggregate behavior to a mixture with a more pronounced J-aggregate behavior upon raising the temperature. It isassumed that both characteristic aggregate bands correlate in borderline cases with two polymer structures which can be assigned to a zig-zag and a helical structure. As no experimental evidence for these structures could hitherto be provided by NMR, TD-DFT computations on oligomers (22-mers) can reproduce very closely the characteristic features of the spectra for the two conformational isomers. The subsequent chapters are motivated by the goal to influence the optical properties through a control of the superstructure and thus of the intramolecular aggregate formation. On the one hand, bulky groups are implemented in the 3-position of the indolenine scaffold to provoke steric repulsion and thus favoring J-aggregate behavior at the expense of helical arrangements. The resulting homopolymer pDiPhSQB bearing two phenyl groups per indolenine exhibits J-type aggregate behavior with red-shifted absorption maxima in all considered solvents which is explained to be caused by the formation of elongated zig-zag structures. Furthermore, single-crystal X-ray analysis of monomer DiPhSQB-2-Br2 reveals a torsion of the indolenine moieties as a consequence of steric congestion. The twist of the molecular geometry and the resulting loss of planarity leads to a serious deterioration of the fluorescence properties, however a significant bathochromic shift of ca. 1 200 cm-1 of the lowest absorption band was observed compared to parent SQB, which is even larger than the shift for dSQB-1 (ca. 1 000 cm-1). On the other hand, a partial stiffening of the polymer backbone is attempted to create a bias for elongated polymer chains. In this respect, the synthetic approach is to replace every second biarylaxis with the rigid transoid benzodipyrrolenine unit. Despite a rather low average degree of polymerization < 10, exclusively red-shifted absorption maxima are observed in all solvents used. In order to complete the picture of intramolecular aggregates through the selective design of H-aggregates, a squaraine-squaraine copolymer was synthesised containing the classic cisoid indolenine as well as the cisoid quinoline building block. Taking advantage of the highly structure directing self-assembly character of the quinoline moiety, the copolymer pSQBC indeed showes a broad, blue-shifted main absorption band in comparison with the monomer unit dSQBC. The shape of the absorption band manifold solely exhibited a minor solvent and temperature dependence indicating a persistent H-aggregate behaviour. Hence, as a proof of concept, it is shown that the optical properties of the polymers (H- and J-aggregate) and the corresponding superstructure can be inherently controlled by an adequate design of monomer precursors. The last chapter of this work deals, in contrast to all other chapters, with intermolecular aggregates. It is shown that the two star-shaped hexasquarainyl benzenes hSQA-1 and hSQA-2 exhibit a strong propensity for self-organisation. Concentration- and temperature-dependent studies reveal a great driving force for self-assembly in acetone. While the larger hSQA-2 instantaneously forms stable aggregates, the aggregates of hSQA-1 shows a pronounced kinetic stability. Taking advantage of the kinetic persistency of these aggregates, the corresponding kinetic activation parameters for aggregation and deaggregation can be assessed. The absorption spectra of both hexasquarainyl benzenes in the aggregated state reveal some striking differences. While hSQA-1 features an intensive, very narrow and blue-shifted absorption band, two red-shifted bands are observed for hSQA-2, which are closely located at the monomer absorption. The very small bandwidth of hSQA-1 are interpreted to be caused by exchange narrowing and pointed towards highly ordered supramolecular aggregates. The concentration-dependent data of the two hexasquarainyl benzenes can be fitted to the dimer-model with excellent correlation coefficients, yielding binding constants in excess of 10^6 M-1, respectively. Such high binding constants are very surprising, considering the unfavourable bulky 3,3-dimethyl groups of the indolenine units which should rather prevent aggregation. Joint theoretical and NMR spectroscopic methods were applied to unravel the supramolecular aggregate structure of hSQA-1, which is shown to consist of two stacked hexasquarainyl benzenes resembling the picture of two stacked bowls.}, subject = {Squaraine}, language = {en} } @article{SchnitzleinZhuShoyamaetal.2022, author = {Schnitzlein, Matthias and Zhu, Chongwei and Shoyama, Kazutaka and W{\"u}rthner, Frank}, title = {π-Extended Pleiadienes by [5+2] Annulation of 1-Boraphenalenes and ortho-Dihaloarenes}, series = {Chemistry - A European Journal}, volume = {28}, journal = {Chemistry - A European Journal}, number = {61}, doi = {10.1002/chem.202202053}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293919}, year = {2022}, abstract = {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.}, language = {en} } @article{SchnitzleinMuetzelShoyamaetal.2022, author = {Schnitzlein, Matthias and M{\"u}tzel, Carina and Shoyama, Kazutaka and Farrell, Jeffrey M. and W{\"u}rthner, Frank}, title = {PAHs Containing both Heptagon and Pentagon: Corannulene Extension by [5+2] Annulation}, series = {European Journal of Organic Chemistry}, volume = {2022}, journal = {European Journal of Organic Chemistry}, number = {5}, doi = {10.1002/ejoc.202101273}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262627}, year = {2022}, abstract = {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.}, language = {en} } @article{SchneiderSchauliesSchumacherWiggeretal.2021, author = {Schneider-Schaulies, Sibylle and Schumacher, Fabian and Wigger, Dominik and Sch{\"o}l, Marie and Waghmare, Trushnal and Schlegel, Jan and Seibel, J{\"u}rgen and Kleuser, Burkhard}, title = {Sphingolipids: effectors and Achilles heals in viral infections?}, series = {Cells}, volume = {10}, journal = {Cells}, number = {9}, issn = {2073-4409}, doi = {10.3390/cells10092175}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-245151}, year = {2021}, abstract = {As viruses are obligatory intracellular parasites, any step during their life cycle strictly depends on successful interaction with their particular host cells. In particular, their interaction with cellular membranes is of crucial importance for most steps in the viral replication cycle. Such interactions are initiated by uptake of viral particles and subsequent trafficking to intracellular compartments to access their replication compartments which provide a spatially confined environment concentrating viral and cellular components, and subsequently, employ cellular membranes for assembly and exit of viral progeny. The ability of viruses to actively modulate lipid composition such as sphingolipids (SLs) is essential for successful completion of the viral life cycle. In addition to their structural and biophysical properties of cellular membranes, some sphingolipid (SL) species are bioactive and as such, take part in cellular signaling processes involved in regulating viral replication. It is especially due to the progress made in tools to study accumulation and dynamics of SLs, which visualize their compartmentalization and identify interaction partners at a cellular level, as well as the availability of genetic knockout systems, that the role of particular SL species in the viral replication process can be analyzed and, most importantly, be explored as targets for therapeutic intervention.}, language = {en} } @article{SchneiderSeebauerBeuerleetal.2024, author = {Schneider, Tilman and Seebauer, Florian and Beuerle, Florian and W{\"u}rthner, Frank}, title = {A monodisperse, end-capped Ru(bda) oligomer with outstanding performance in heterogeneous electrochemical water oxidation}, series = {Advanced Materials Technologies}, volume = {9}, journal = {Advanced Materials Technologies}, number = {11}, issn = {2365-709X}, doi = {10.1002/admt.202301721}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-363133}, year = {2024}, abstract = {AbstractWater oxidation catalysis is a key step for sustainable fuel production by water splitting into hydrogen and oxygen. The synthesis of a novel coordination oligomer based on four Ru(bda) (bda = 2,2′-bipyridine-6,6′-dicarboxylate) centers, three 4,4′-bipyridine (4,4′-bpy) linkers, and two 4-picoline (4-pic) end caps is reported. The monodispersity of this tetranuclear compound is characterized by NMR techniques. Heterogeneous electrochemical water oxidation after immobilization on multi-walled carbon nanotubes (MWCNTs) shows catalytic performance unprecedented for this compound class, with a turnover frequency (TOF) of 133 s\(^{-1}\) and a turnover number (TON) of 4.89 × 10\(^6\), at a current density of 43.8 mA cm\(^{-2}\) and a potential of 1.45 V versus normal hydrogen electrode (NHE).}, language = {en} } @phdthesis{Schmidt2008, author = {Schmidt, R{\"u}diger}, title = {Perylene Bisimide and Acene Derivatives as Organic Semiconductors in OTFTs}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-29314}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {This thesis deals with the synthesis of improved organic semiconductors, the detailed investigation of the molecular properties and the solid state arrangements revealed by single crystal X-ray diffraction and finally the development of structureperformance dependencies by measuring of the charge carrier mobilities of the derivatives in thin film transistors. The two main-goals of this thesis were achieved. Well soluble acene derivatives for spin-coated TFTs were obtained, showing charge carrier mobilities in the range of polymer p-type materials. Novel core-fluorinated perylene bisimide dyes were synthesized particularly and the use of electron deficient substituents lead to PBIs with outstanding air-stable mobilities in thin film transistors prepared by vacuum deposition techniques. The relationship between performance, air stability and solid state packing was elucidated in detail by single crystal X-ray diffraction analysis.}, subject = {D{\"u}nnschichttransistor}, language = {en} } @phdthesis{Schmidt2011, author = {Schmidt, Ralf}, title = {Hamilton-Receptor-Mediated Self-Assembly of Merocyanine Dyes into Supramolecular Polymers}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-56265}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2011}, abstract = {Die Selbstorganisation von Merocyaninfarbstoffen zu supramolekularen Polymeren wurde untersucht. Dabei konnte die Anordnung der hoch dipolaren Farbstoffe durch die Verwendung von verschiedenen Kombinationen von Wasserstoffbr{\"u}ckenbindungsmotiven und dipolarer Aggregation der Chromophore gesteuert.}, subject = {Selbstorganisation}, language = {en} } @article{SchmidtStolteSuessetal.2019, author = {Schmidt, David and Stolte, Matthias and S{\"u}ß, Jasmin and Liess, Dr. Andreas and Stepanenko, Vladimir and W{\"u}rthner, Frank}, title = {Protein-like enwrapped perylene bisimide chromophore as bright microcrystalline emitter material}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {38}, doi = {10.1002/ange.201907618}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204809}, pages = {13385-13389}, year = {2019}, abstract = {Strongly emissive solid-state materials are mandatory components for many emerging optoelectronic technologies, but fluorescence is often quenched in the solid state owing to strong intermolecular interactions. The design of new organic pigments, which retain their optical properties despite their high tendency to crystallize, could overcome such limitations. Herein, we show a new material with monomer-like absorption and emission profiles as well as fluorescence quantum yields over 90 \% in its crystalline solid state. The material was synthesized by attaching two bulky tris(4-tert-butylphenyl)phenoxy substituents at the perylene bisimide bay positions. These substituents direct a packing arrangement with full enwrapping of the chromophore and unidirectional chromophore alignment within the crystal lattice to afford optical properties that resemble those of their natural pigment counterparts, in which chromophores are rigidly embedded in protein environments.}, language = {en} } @phdthesis{Schlund2007, author = {Schlund, Sebastian}, title = {Quantifying Non-covalent Interactions - Rational in-silico Design of Guanidinium-based Carboxylate Receptors}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-24388}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2007}, abstract = {Die nat{\"u}rlichen Vorbilder effektiver Anionenrezeptoren sind Enzyme, welche oftmals Arginin als entscheidende Aminos{\"a}ure in der Bindungstasche tragen. Die positiv geladenene Guanidiniumgruppe, wie sie in der Seitenkette von Arginin vorkommt, ist daher das zentrale Strukturmerkmal f{\"u}r viele k{\"u}nstliche Anionenrezeptoren. Im Jahre 1999 gelang es Schmuck und Mitarbeitern eine neue Klasse von Guanidinium-basierten Oxoanionenrezeptoren zu entwickeln, die Carboxylate sogar in w{\"a}ssrigen Medien binden k{\"o}nnen. Die Bindungsmodi der 2-(Guanidiniocarbonyl)-1H-pyrrole basieren auf einer Kombination von einzeln betrachtet schwachen nicht-kovalenten Wechselwirkungen wie Ionenpaarbildung und multiplen Wasserstoffbr{\"u}ckenbindungen zwischen k{\"u}nstlichem Rezeptor und Substrat. Durch Substitution einer Carboxylatgruppe in Position 5 des Pyrrolringes erh{\"a}lt man ein zwitterionisches Derivat welches sich in Wasser mit einer Assoziationskonstante von sch{\"a}tzungsweise 170 M-1 zu einzelnen Dimeren zusammenlagert (Dimer 1). Um das Strukturmotiv hinsichtlich einer noch effektiveren Anionenbindung weiter verbessern zu k{\"o}nnen, ist es daher von großem Interesse, die verschiedenartigen intermolekularen Wechselwirkungen zwischen den beiden monomeren Einheiten von Dimer 1 zu quantifizieren. Vor diesem Hintergrund wurden verschiedene theoretische ab initio Studien durchgef{\"u}hrt, um die Einfl{\"u}sse von intrinsischen Eigenschaften sowie von Solvenseffekten auf die Stabilit{\"a}t sich selbst zusammenlagernden Dimeren aufzukl{\"a}ren. In Kapitel 4.1 wurden die molekularen Wechselwirkungen im Dimer 1 durch Vergleich mit verschiedenen „Knock-out" Analoga untersucht. In diesen Analoga wurden einzelne Wasserstoffbr{\"u}ckenbindungen durch Substitution von Wasserstoffdonoren mit Methylengruppen oder Etherbr{\"u}cken ausgeschaltet. Es konnte gezeigt werden, dass die Anwendung eines vereinfachten Kontinuum-Solvensmodells nicht ausreicht, die absoluten Energien der „Knock-out" Analoga in stark polaren L{\"o}sungsmitteln vorherzusagen, jedoch k{\"o}nnen die berechneten Trends Auskunft {\"u}ber die relativen Stabilit{\"a}ten geben. In Kapitel 4.2 wurde die strukturelle {\"A}hnlichkeit von Arginin mit Struktur 1 ausgenutzt, um die Abh{\"a}ngigkeit der St{\"a}rke der Dimerisierung von der Flexibilit{\"a}t der molekularen Struktur eingehender zu untersuchen. In Kapitel 4.2.1 wurden neue globale Minimumsstrukturen des kanonischen und zwitterionischen Arginins in der Gasphase bestimmt. Dies geschah mit Hilfe von umfangreichen kraftfeldbasierten Konformationssuchen in Verbindung mit ab initio Strukturoptimierungen der energetisch niedrigsten Konformere. Die meisten der neu identifizierten Minimumskonformere sowohl des zwitterionischen als auch des kanonischen Tautomers zeigten geometrische Anordnungen mit bis dahin unbekannten gestapelten Orientierungen der endst{\"a}ndigen Gruppen. Es wurde letztendlich eine neuartige globale Minimumsstruktur (N1) gefunden, welche eine um mehr als 8 kJ mol-1 niedrigere Energie besitzt als die bislang ver{\"o}ffentlichten Konformere. Die gleiche Strategie f{\"u}r das Auffinden von energetischen Minimumskonformeren, wie sie bereits f{\"u}r das Arginin Monomer benutzt wurde, wurde auch im Falle der Dimere von Arginin verwendet. Im Gegensatz zu vorhergehenden theoretischen Untersuchungen ist die neue globale Minimumsstruktur ungef{\"a}hr 60 kJ mol-1 stabiler und weist ebenfalls eine gestapelte Orientierung der Guanidinium- und Carboxylatgruppen auf. Der Einfluss der Rigidit{\"a}t auf die Dimerstabilit{\"a}t wurde durch Berechnungen eines k{\"u}nstlich versteiften Arginin Dimersystems bewiesen. Die hohe Bindungsaffinit{\"a}t des Dimers 1 ergibt sich daher zu etwa 50\% aus der Rigidit{\"a}t der Monomere, welche jegliche intramolekulare Stabilisierung verhindert. Um Vorschl{\"a}ge f{\"u}r ein verbessertes Carboxylatbindungsmotiv machen zu k{\"o}nnen, wurden in Kapitel 4.3 neuartige Strukturmotive mit ver{\"a}nderten Ringsystemen auf DFT Niveau untersucht. Die direkte Abh{\"a}ngigkeit der Dimerisierungsenergie von einem zunehmenden Dipolmoment wurde durch verschiedene anellierte Ringstrukturen bewiesen. Der Einfluss der Delokalisierung in den Monomeren auf die Dimerisierungsenergie wurde durch Ver{\"a}nderung der Elektronenstruktur von elektronisch entkoppelten Biphenylenen untersucht. Es konnte gezeigt werden, dass die Carbonylfunktion haupts{\"a}chlich f{\"u}r eine gute Pr{\"a}organisation verantwortlich ist, wohingegen der Effekt auf die Azidit{\"a}t eine geringere Bedeutung besitzt. Im letzten Kapitel wurden Kooperativit{\"a}tseffekte in supramolekularen Systemen untersucht. Als Modellsysteme dienten hierbei Adenosin-Carbons{\"a}ure-Komplexe, deren berechnete NMR Verschiebungen mit experimentellen Niedrigtemperatur-NMR-Studien verglichen wurden. Wir konnten zeigen, dass nur durch die Verwendung von schwingungsgemittelten NMR Verschiebungen die experimentelle Protonenverschiebung reproduziert werden kann, welche unter Tieftemperaturbedingungen im Austauschregime von Wasserstoffbr{\"u}ckenbindungen erhalten wurde.}, subject = {nicht-kovalente Wechselwirkungen}, language = {en} } @article{SchlosserCibulkaGrossetal.2020, author = {Schlosser, Julika and Cibulka, Radek and Groß, Philipp and Ihmels, Heiko and Mohrschladt, Christian J.}, title = {Visible-Light-Induced Di-\(\pi\)-Methane Rearrangement of Dibenzobarrelene Derivatives}, series = {ChemPhotoChem}, volume = {4}, journal = {ChemPhotoChem}, number = {2}, doi = {10.1002/cptc.201900221}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212633}, pages = {132 -- 137}, year = {2020}, abstract = {It is demonstrated that the di-\(\pi\)-methane (DPM) rearrangement of carbonyl-substituted dibenzobarrelene (9,10-dihydro-9,10-ethenoanthracene) derivatives is induced by visible-light-induced triplet photosensitization with Ir(ppy)\(_{3}\), Ir(dFppy)\(_{3}\) or 1-butyl-7,8-dimethoxy-3-methylalloxazine as catalysts, whereas derivatives that lack carbonyl substituents are photoinert under these conditions. Notably, the products are formed almost quantitatively.}, language = {en} } @article{SchlossarekStepanenkoBeuerleetal.2022, author = {Schlossarek, Tim and Stepanenko, Vladimir and Beuerle, Florian and W{\"u}rthner, Frank}, title = {Self-assembled Ru(bda) Coordination Oligomers as Efficient Catalysts for Visible Light-Driven Water Oxidation in Pure Water}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {52}, doi = {10.1002/anie.202211445}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312184}, year = {2022}, abstract = {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.}, language = {en} } @article{SchlauersbachHanioLenzetal.2021, author = {Schlauersbach, Jonas and Hanio, Simon and Lenz, Bettina and Vemulapalli, Sahithya P. B. and Griesinger, Christian and P{\"o}ppler, Ann-Christin and Harlacher, Cornelius and Galli, Bruno and Meinel, Lorenz}, title = {Leveraging bile solubilization of poorly water-soluble drugs by rational polymer selection}, series = {Journal of Controlled Release}, volume = {330}, journal = {Journal of Controlled Release}, edition = {Accepted Version}, doi = {10.1016/j.jconrel.2020.12.016}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-296957}, pages = {36-48}, year = {2021}, abstract = {Poorly water-soluble drugs frequently solubilize into bile colloids and this natural mechanism is key for efficient bioavailability. We tested the impact of pharmaceutical polymers on this solubilization interplay using proton nuclear magnetic resonance spectroscopy, dynamic light scattering, and by assessing the flux across model membranes. Eudragit E, Soluplus, and a therapeutically used model polymer, Colesevelam, impacted the bile-colloidal geometry and molecular interaction. These polymer-induced changes reduced the flux of poorly water-soluble and bile interacting drugs (Perphenazine, Imatinib) but did not impact the flux of bile non-interacting Metoprolol. Non-bile interacting polymers (Kollidon VA 64, HPMC-AS) neither impacted the flux of colloid-interacting nor colloid-non-interacting drugs. These insights into the drug substance/polymer/bile colloid interplay potentially point towards a practical optimization parameter steering formulations to efficient bile-solubilization by rational polymer selection.}, language = {en} } @article{SchindlerMezaChinchaRothetal.2021, author = {Schindler, Dorothee and Meza-Chincha, Anna-Lucia and Roth, Maximilian and W{\"u}rthner, Frank}, title = {Structure-Activity Relationship for Di- up to Tetranuclear Macrocyclic Ruthenium Catalysts in Homogeneous Water Oxidation}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {68}, doi = {10.1002/chem.202100549}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256792}, pages = {16938-16946}, year = {2021}, abstract = {Two di- and tetranuclear Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylate) macrocyclic complexes were synthesized and their catalytic activities in chemical and photochemical water oxidation investigated in a comparative manner to our previously reported trinuclear congener. Our studies have shown that the catalytic activities of this homologous series of multinuclear Ru(bda) macrocycles in homogeneous water oxidation are dependent on their size, exhibiting highest efficiencies for the largest tetranuclear catalyst. The turnover frequencies (TOFs) have increased from di- to tetranuclear macrocycles not only per catalyst molecule but more importantly also per Ru unit with TOF of 6 \(^{-1}\) to 8.7 \(^{-1}\) and 10.5 s\(^{-1}\) in chemical and 0.6 s\(^{-1}\) to 3.3 \(^{-1}\) and 5.8 \(^{-1}\) in photochemical water oxidation per Ru unit, respectively. Thus, for the first time, a clear structure-activity relationship could be established for this novel class of macrocyclic water oxidation catalysts.}, language = {en} } @article{SchindlerGil‐SepulcreLindneretal.2020, author = {Schindler, Dorothee and Gil-Sepulcre, Marcos and Lindner, Joachim O. and Stepanenko, Vladimir and Moonshiram, Dooshaye and Llobet, Antoni and W{\"u}rthner, Frank}, title = {Efficient Electrochemical Water Oxidation by a Trinuclear Ru(bda) Macrocycle Immobilized on Multi-Walled Carbon Nanotube Electrodes}, series = {Advanced Energy Materials}, volume = {10}, journal = {Advanced Energy Materials}, number = {43}, doi = {10.1002/aenm.202002329}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218381}, year = {2020}, abstract = {Catalytic water splitting is a viable process for the generation of renewable fuels. Here it is reported for the first time that a trinuclear supramolecular Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylate) catalyst, anchored on multi-walled carbon nanotubes and subsequently immobilized on glassy carbon electrodes, shows outstanding performance in heterogeneous water oxidation. Activation of the catalyst on anodes by repetitive cyclic voltammetry (CV) scans results in a catalytic current density of 186 mA cm\(^{-2}\) at a potential of 1.45 V versus NHE. The activated catalyst performs water oxidation at an onset overpotential of 330 mV. The remarkably high stability of the hybrid anode is demonstrated by X-ray absorption spectroscopy and electrochemically, revealing the absence of any degradation after 1.8 million turnovers. Foot of the wave analysis of CV data of activated electrodes with different concentrations of catalyst indicates a monomolecular water nucleophilic attack mechanism with an apparent rate constant of TOFmax (turnover frequency) of 3200 s\(^{-1}\).}, language = {en} } @phdthesis{Schindler2022, author = {Schindler, Dorothee}, title = {Water Oxidation with Multinuclear Ruthenium Catalysts}, doi = {10.25972/OPUS-23309}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-233093}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {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.}, subject = {Rutheniumkomplexe}, language = {en} } @article{SchembriKimLiessetal.2021, author = {Schembri, Tim and Kim, Jin Hong and Liess, Andreas and Stepanenko, Vladimir and Stolte, Matthias and W{\"u}rthner, Frank}, title = {Semitransparent Layers of Social Self-Sorting Merocyanine Dyes for Ultranarrow Bandwidth Organic Photodiodes}, series = {Advanced Optical Materials}, volume = {9}, journal = {Advanced Optical Materials}, number = {15}, doi = {10.1002/adom.202100213}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-244762}, year = {2021}, abstract = {Two dipolar merocyanines consisting of the same π-conjugated chromophore but different alkyl substituents adopt very different packing arrangements in their respective solid state with either H- or J-type exciton coupling, leading to ultranarrow absorption bands at 477 and 750 nm, respectively, due to exchange narrowing. The social self-sorting behavior of these push-pull chromophores in their mixed thin films is evaluated and the impact on morphology as well as opto-electronical properties is determined. The implementation of this well-tuned two-component material with tailored optical features allows to optimize planar heterojunction organic photodiodes with fullerene ​(C\(_{60}\)) with either dual or single wavelength selectivity in the blue and NIR spectral range with ultranarrow bandwidths of only 11 nm (200 cm\(^{-1}\)) and an external quantum efficiency of up to 18\% at 754 nm under 0 V bias. The application of these photodiodes as low-power consuming heart rate monitors is demonstrated by a reflectance-mode photoplethysmography (PPG) sensor.}, language = {en} } @unpublished{ScheitlGhaemMaghamiLenzetal.2020, author = {Scheitl, Carolin P.M. and Ghaem Maghami, Mohammad and Lenz, Ann-Kathrin and H{\"o}bartner, Claudia}, title = {Site-specific RNA methylation by a methyltransferase ribozyme}, series = {Nature}, journal = {Nature}, doi = {10.1038/s41586-020-2854-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218687}, year = {2020}, abstract = {Nearly all classes of coding and non-coding RNA undergo post-transcriptional modification including RNA methylation. Methylated nucleotides belong to the evolutionarily most conserved features of tRNA and rRNA.1,2 Many contemporary methyltransferases use the universal cofactor S-adenosylmethionine (SAM) as methyl group donor. This and other nucleotide-derived cofactors are considered as evolutionary leftovers from an RNA World, in which ribozymes may have catalysed essential metabolic reactions beyond self-replication.3 Chemically diverse ribozymes seem to have been lost in Nature, but may be reconstructed in the laboratory by in vitro selection. Here, we report a methyltransferase ribozyme that catalyses the site-specific installation of 1-methyladenosine (m1A) in a substrate RNA, utilizing O6-methylguanine (m6G) as a small-molecule cofactor. The ribozyme shows a broad RNA sequence scope, as exemplified by site-specific adenosine methylation in tRNAs. This finding provides fundamental insights into RNA's catalytic abilities, serves a synthetic tool to install m1A in RNA, and may pave the way to in vitro evolution of other methyltransferase and demethylase ribozymes.}, language = {en} } @article{ScheitlOkudaAdelmannetal.2023, author = {Scheitl, Carolin P. M. and Okuda, Takumi and Adelmann, Juliane and H{\"o}bartner, Claudia}, title = {Ribozyme-catalyzed late-stage functionalization and fluorogenic labeling of RNA}, series = {Angewandte Chemie International Edition}, volume = {62}, journal = {Angewandte Chemie International Edition}, doi = {10.1002/anie.202305463}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-327543}, year = {2023}, abstract = {Site-specific introduction of biorthogonal handles into RNAs is in high demand for decorating RNAs with fluorophores, affinity labels or other modifications. Aldehydes represent attractive functional groups for post-synthetic bioconjugation reactions. Here, we report a ribozyme-based method for the synthesis of aldehyde-functionalized RNA by directly converting a purine nucleobase. Using the methyltransferase ribozyme MTR1 as an alkyltransferase, the reaction is initiated by site-specific N1 benzylation of purine, followed by nucleophilic ring opening and spontaneous hydrolysis under mild conditions to yield a 5-amino-4-formylimidazole residue in good yields. The modified nucleotide is accessible to aldehyde-reactive probes, as demonstrated by the conjugation of biotin or fluorescent dyes to short synthetic RNAs and tRNA transcripts. Upon fluorogenic condensation with a 2,3,3-trimethylindole, a novel hemicyanine chromophore was generated directly on the RNA. This work expands the MTR1 ribozyme's area of application from a methyltransferase to a tool for site-specific late-stage functionalization of RNA.}, language = {en} } @unpublished{ScheitlMieczkowskiSchindelinetal.2022, author = {Scheitl, Carolin P. M. and Mieczkowski, Mateusz and Schindelin, Hermann and H{\"o}bartner, Claudia}, title = {Structure and mechanism of the methyltransferase ribozyme MTR1}, series = {Nature Chemical Biology}, journal = {Nature Chemical Biology}, edition = {submitted version}, doi = {10.1038/s41589-022-00976-x}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-272170}, year = {2022}, abstract = {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 {\AA}, 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.}, language = {en} } @article{ScheitlLangeHoebartner2020, author = {Scheitl, Carolin P. M. and Lange, Sandra and H{\"o}bartner, Claudia}, title = {New deoxyribozymes for the native ligation of RNA}, series = {Molecules}, volume = {25}, journal = {Molecules}, number = {16}, doi = {https://doi.org/10.3390/molecules25163650}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-210405}, year = {2020}, abstract = {Deoxyribozymes (DNAzymes) are small, synthetic, single-stranded DNAs capable of catalysing chemical reactions, including RNA ligation. Herein, we report a novel class of RNA ligase deoxyribozymes that utilize 5'-adenylated RNA (5'-AppRNA) as the donor substrate, mimicking the activated intermediates of protein-catalyzed RNA ligation. Four new DNAzymes were identified by in vitro selection from an N40 random DNA library and were shown to catalyze the intermolecular linear RNA-RNA ligation via the formation of a native 3'-5'-phosphodiester linkage. The catalytic activity is distinct from previously described RNA-ligating deoxyribozymes. Kinetic analyses revealed the optimal incubation conditions for high ligation yields and demonstrated a broad RNA substrate scope. Together with the smooth synthetic accessibility of 5'-adenylated RNAs, the new DNA enzymes are promising tools for the protein-free synthesis of long RNAs, for example containing precious modified nucleotides or fluorescent labels for biochemical and biophysical investigations.}, language = {en} } @phdthesis{Scheitl2023, author = {Scheitl, Carolin P. M.}, title = {In vitro selected ribozymes for RNA methylation and labeling}, doi = {10.25972/OPUS-33004}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-330049}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {The focus of this work was the development and application of highly efficient RNA catalysts for the site-specific modification of RNA with special focus on methylation. In the course of this thesis, the first methyltransferase ribozyme (MTR1), which uses m6G as the methyl group donor was developed and further characterized. The RNA product was identified as the natural modification m1A. X-Ray crystallography was used to solve the 3D structure of the ribozyme, which directly suggested a plausible reaction meachnism. The MTR1 ribozyme was also successfully repurposed for a nucleobase transformation reaction of a purine nucleoside. This resulted in a formyl-imidazole moiety directly on the intact RNA, which was directly used for further bioconjugation reactions. Finally, additional selections and reselections led to the identification of highly active alkyltransferase ribozymes that can be used for the labeling of various RNA targets}, subject = {Methylierung}, language = {en} } @article{ScheidelOestreicherMarketal.2022, author = {Scheidel, Sebastian and {\"O}streicher, Laurina and Mark, Isabelle and P{\"o}ppler, Ann-Christin}, title = {You cannot fight the pressure: Structural rearrangements of active pharmaceutical ingredients under magic angle spinning}, series = {Magnetic Resonance in Chemistry}, volume = {60}, journal = {Magnetic Resonance in Chemistry}, number = {6}, doi = {10.1002/mrc.5267}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318838}, pages = {572 -- 582}, year = {2022}, abstract = {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.}, language = {en} } @phdthesis{Sapotta2021, author = {Sapotta, Meike}, title = {Perylene Bisimide Cyclophanes: Recognition of Alkaloids, Aggregation Behavior in Aqueous Environment and Guest-Mediated Chirality Transfer}, doi = {10.25972/OPUS-20002}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200028}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Inspired by the fact that sufficient solubility in aqueous media can be achieved by functional substitution of perylene bisimides (PBIs) with polar groups, one of the essential aims of this thesis was the design and successful synthesis of the new water-soluble PBI cyclophanes [2PBI]-1m and [2PBI]-1p, which are appended with branched, hydrophilic oligoethylene glycol (OEG) chains. Subsequently, the focus was set on the elucidation of properties of PBI cyclophane hosts which are also of relevance for recognition processes in biological systems. The performance of the new amphiphilic PBI cyclophane [2PBI]-1p as synthetic receptors for various natural aromatic alkaloids in aqueous media was thoroughly investigated. Alkaloids represent a prominent class of ubiquitous nitrogen containing natural compounds with a great structural variety and diverse biological activity. As of yet, no chromophore host acting as a molecular probe for a range of alkaloids such as harmine or harmaline is known. In addition, the self-association behavior of cyclophane host [2PBI]-1m and its reference monomer in water was studied in order to gain insights into the thermodynamic driving forces affecting the self-assembly process of these two PBI systems in aqueous environment. Moreover, the chirality transfer upon guest binding previously observed for a PBI cyclophane was investigated further. The assignment of the underlying mechanism of guest recognition to either the induced fit or conformational selection model was of particular interest.}, subject = {Supramolekulare Chemie}, language = {en} } @article{SanchezNayaStepanenkoMandeletal.2021, author = {Sanchez-Naya, Roberto and Stepanenko, Vladimir and Mandel, Karl and Beuerle, Florian}, title = {Modulation of Crystallinity and Optical Properties in Composite Materials Combining Iron Oxide Nanoparticles and Dye-Containing Covalent Organic Frameworks}, series = {Organic Materials}, volume = {3}, journal = {Organic Materials}, doi = {10.1055/s-0040-1722655}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231480}, pages = {17-24}, year = {2021}, abstract = {Two series of organic-inorganic composite materials were synthesized through solvothermal imine condensation between diketopyrrolopyrrole dialdehyde DPP-1 and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) in the presence of varying amounts of either amino- or carboxy-functionalized superparamagnetic iron oxide nanoparticles (FeO). Whereas high FeO loading induced cross-linking of the inorganic nanoparticles by amorphous imine polymers, a lower FeO content resulted in the formation of crystalline covalent organic framework domains. All hybrid materials were analyzed by magnetization measurements, powder X-ray diffraction, electron microscopy, IR, and UV/Vis absorption spectroscopy. Crystallinity, chromophore stacking, and visible absorption features are directly correlated to the mass fraction of the components, thus allowing for a fine-tuning of materials properties.}, language = {en} } @phdthesis{SafontSempere2010, author = {Safont Sempere, Marina Montserrat}, title = {Chiral self-sorting of atropo-enantiomeric perylene bisimide dyes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-55359}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {This thesis included the synthesis of conformationally stable chiral perylene bisimide (PBI) dyes, the study of their optical properties in solution and their chiral self-sorting behaviour in nonpolar solvents in which dimerization via pi-pi-stacking takes place. Furthermore, the influence of PBI core chirality on the properties of these dyes in the condensed state has been also studied. We have demonstrated and quantified the prevalence of chiral self-recognition over self-discrimination in pi-stacking dimerization of PBIs. It has been shown that this self-recognition event is compromised by the increasing flexibility of the structures related to the size of the OEG bridging units. Moreover, the inherent chirality of these PBIs has been proven to strongly influence their condensed state properties, for which large differences between the pure enantiomers and the racemates were revealed, as well as between the different bridged macrocyclic PBIs.}, subject = {Farbstoff}, language = {en} } @unpublished{SaalSwainSchmiedeletal.2023, author = {Saal, Fridolin and Swain, Asim and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Ravat, Prince}, title = {Push-Pull [7]Helicene Diimide: Excited-State Charge Transfer and Solvatochromic Circularly Polarised Luminescence}, edition = {submitted version}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-345207}, year = {2023}, abstract = {In this communication we describe a helically chiral push-pull molecule named 9,10-dimethoxy-[7]helicene diimide, displaying fluorescence (FL) and circularly polarised luminescence (CPL) over nearly the entire visible spectrum dependent on solvent polarity. The synthesised molecule exhibits an unusual solvent polarity dependence of FL quantum yield and nonradiative rate constant, as well as remarkable gabs and glum values along with high configurational stability.}, language = {en} } @article{Roehr2021, author = {R{\"o}hr, Merle I. S.}, title = {New theoretical methods for the exploration of functional landscapes}, series = {International Journal of Quantum Chemistry}, volume = {121}, journal = {International Journal of Quantum Chemistry}, number = {24}, doi = {10.1002/qua.26747}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257682}, year = {2021}, abstract = {Molecular functionality can be often directly attributed to given properties of the electronic wavefunction. Analogous to the potential energy surface, these properties can be represented as a function of the nuclear coordinates, giving rise to molecular "functional landscapes." However, so far there has been no possibility for their systematic investigation. This perspective aims to discuss the development of new theoretical methods based on the multistate extension of the metadynamics approach, employing electronic collective variables. This emerging methodology allows to explore functional landscapes and to gain a deeper understanding of the structure-function relation in molecules and complex molecular systems in the ground and excited electronic state.}, language = {en} } @phdthesis{Roeger2007, author = {R{\"o}ger, Cornelia}, title = {Bioinspired Light-Harvesting Zinc Chlorin Rod Aggregates Powered by Peripheral Chromophores}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-26760}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2007}, abstract = {Artificial light-harvesting (LH) systems have been obtained by self-assembly of naphthalene diimide-functionalized zinc chlorin dyads and triad in nonpolar, aprotic solvents. UV-vis, CD, and steady-state emission spectroscopy as well as atomic force microscopy showed that rod-like structures are formed by excitonic interactions of zinc chlorin units, while the appended naphthalene diimide dyes do not aggregate at the periphery of the cylinders. In all cases, photoexcitation of the enveloping naphthalene diimides at 540 and 620 nm, respectively, was followed by highly efficient energy-transfer processes to the inner zinc chlorin backbone, as revealed by time-resolved fluorescence spectroscopy on the picosecond time-scale. As a consequence, the LH efficiencies of zinc chlorin rod aggregates were increased by up to 63\%. The effective utilization of solar energy recommends these biomimetic systems for an application in electronic materials on the nanoscale.}, subject = {Farbstoff}, language = {en} } @article{RushdiAbdelRahmanAttiaetal.2022, author = {Rushdi, Mohammed I. and Abdel-Rahman, Iman A. M. and Attia, Eman Zekry and Saber, Hani and Saber, Abdullah A. and Bringmann, Gerhard and Abdelmohsen, Usama Ramadan}, title = {The biodiversity of the genus Dictyota: phytochemical and pharmacological natural products prospectives}, series = {Molecules}, volume = {27}, journal = {Molecules}, number = {3}, issn = {1420-3049}, doi = {10.3390/molecules27030672}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-302428}, year = {2022}, abstract = {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.}, language = {en} } @phdthesis{Roos2021, author = {Roos, Markus}, title = {Synthesis, Photophysics and Photocatalysis of [FeFe] Complex Containing Dyads and Bimolecular Systems}, doi = {10.25972/OPUS-23453}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234537}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {In the course of this work, a total of three photocatalytically active dyads for proton reduction could be synthesized together with the associated individual components. Two of them, D1 and D2, comprised a [Ru(bpy)3]2+ photosensitizer and D3 an [Ir(ppy)2bpy]+ photosensitizer. A Ppyr3-substituted propyldithiolate [FeFe] complex was used as catalyst in all systems. The absorption spectroscopic and electrochemical investigations showed that an inner-dyadic electronic coupling is effectively prevented in the dyads due to conjugation blockers within the bridging units used. The photocatalytic investigations exhibited that all dyad containing two-component systems (2CS) showed a significantly worse performance than the corresponding bimolecular three-component systems (3CS). Transient absorption spectroscopy showed that the 2CS behave very similarly to the associated multicomponent systems during photocatalysis. The electron that was intended for the intramolecular transfer from the photosensitizer unit to the catalyst unit within the dyads remains at the photosensitizer for a relatively long time, analogous to the 3CS and despite the covalently bound catalyst. It is therefore assumed that this intramolecular electron transfer is likely to be hindered as a result of the weak electronic coupling caused by the bridge units used. Instead, the system bypasses this through an intermolecular transfer to other dyad molecules in the immediate vicinity. In addition, with the help of emission quenching experiments and electrochemical investigations, it could be clearly concluded that all investigated systems proceed via the reductive quenching mechanism during photocatalysis.}, subject = {Fotokatalyse}, language = {en} } @article{RonaldHoebartner2020, author = {Ronald, Micura and H{\"o}bartner, Claudia}, title = {Fundamental studies of functional nucleic acids: aptamers, riboswitches, ribozymes and DNAzymes}, series = {Chemical Society Reviews}, journal = {Chemical Society Reviews}, edition = {Advance Article}, doi = {10.1039/D0CS00617C}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212133}, year = {2020}, abstract = {This review aims at juxtaposing common versus distinct structural and functional strategies that are applied by aptamers, riboswitches, and ribozymes/DNAzymes. Focusing on recently discovered systems, we begin our analysis with small-molecule binding aptamers, with emphasis on in vitro-selected fluorogenic RNA aptamers and their different modes of ligand binding and fluorescence activation. Fundamental insights are much needed to advance RNA imaging probes for detection of exo- and endogenous RNA and for RNA process tracking. Secondly, we discuss the latest gene expression-regulating mRNA riboswitches that respond to the alarmone ppGpp, to PRPP, to NAD+, to adenosine and cytidine diphosphates, and to precursors of thiamine biosynthesis (HMP-PP), and we outline new subclasses of SAM and tetrahydrofolate-binding RNA regulators. Many riboswitches bind protein enzyme cofactors that, in principle, can catalyse a chemical reaction. For RNA, however, only one system (glmS ribozyme) has been identified in Nature thus far that utilizes a small molecule - glucosamine-6-phosphate - to participate directly in reaction catalysis (phosphodiester cleavage). We wonder why that is the case and what is to be done to reveal such likely existing cellular activities that could be more diverse than currently imagined. Thirdly, this brings us to the four latest small nucleolytic ribozymes termed twister, twister-sister, pistol, and hatchet as well as to in vitro selected DNA and RNA enzymes that promote new chemistry, mainly by exploiting their ability for RNA labelling and nucleoside modification recognition. Enormous progress in understanding the strategies of nucleic acids catalysts has been made by providing thorough structural fundaments (e.g. first structure of a DNAzyme, structures of ribozyme transition state mimics) in combination with functional assays and atomic mutagenesis.}, language = {en} } @phdthesis{Roger2024, author = {Roger, Chantal}, title = {Photophysics and Spin Chemistry of Triptycene Bridge Donor-Acceptor-Triads}, doi = {10.25972/OPUS-36303}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-363031}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {The goal of this thesis was to investigate the influence of rotational restriction between individual parts and of the varying electron density in the bridging unit of D B A systems on the exchange interaction 2J, and thus the electronic coupling between a donor state and an acceptor state. A better understanding of how to influence the underlaying spin dynamics in such donor acceptor systems can open up the door to new technologies, such as modern molecular electronics or optoelectronic devices. Therefore, three series of molecules consisting of a TAA electron donor, a TTC or ATC bridging unit and a PDI electron acceptor were studied. To investigate the influence of rotational restriction on 2J and the electronic coupling, a series of four rotationally hindered triads (chapter 6) was synthesised. The dihedral angle between the TAA and the TTC as well as between the TTC and the PDI was restricted by ortho methyl groups at the phenylene linkers of the connecting ends to the TTC bridge, producing a twist around the linking single bond which minimises the π overlap. The triads exhibit varying numbers of ortho methyl groups and therefore different degrees of rotational restriction. In order to shine light on the influence of varying electron density on 2J and the electronic coupling, a series of four substituted triptycene triads (chapter 7) was synthesised. The electron density in the TTC bridging unit was varied by electron donating and electron withdrawing groups in 12,13 position of the TTC bridging unit and thus varying its HOMO/LUMO energy. The last series of two anthracene bridge triads (chapter 8) connected both approaches by restricting the rotation with ortho methyl groups and simultaneously by varying the bridge energies. In order to obtain the electronic properties, steady state absorption and emission spectra of all triads were investigated (chapter 4). Here, all triads show spectral features associated with the separate absorption bands of TAA and the PDI moiety. The reduced QYs, compared to the unsubstituted PDI acceptor, indicate a non radiative quenching mechanism in all triads. The CV data (chapter 5) were used to calculate the energies of possible CSSs and those results were used to assign the CR dynamics into the different Marcus regions. fs TA measurements reveal that all triads form a CSS upon excitation of the PDI moiety. The lifetimes of the involved states and the rate constants were determined by global exponential fits and global target analysis. The CR dynamics upon depopulation of the CSSs were investigated using external magnetic field dependent ns TA spectroscopy. The ns TA maps show that all triads recombine via CRT pathway populating the local 3PDI state in toluene and provided the respective lifetimes. The approximate QYs of triplet formation were determined using actinometry. The magnetic field dependent ns TA data reveal the exchange interaction 2J between singlet and triplet CSS for each triad. Those magnetic field dependent ns TA data in toluene were furthermore treated using a quantum mechanical simulation (done by U.E. Steiner) to extract the rate constants kT and kS for CRT and CRS, respectively. However, the error margins of kS were rather wide. Finally, the electronic couplings between the donor and the acceptor states were obtained by combining the aforementioned experimental results of the rate constants and applying the Bixon Jortner theoretical description of diabatic ET and Andersons perturbative theory of the exchange coupling. Therefore, the experimentally determined values of 2J and the calculated values of kCS and kT were used. The rate constant kS was calculated based on the electronic coupling V1CSS 1S0. The rotationally hindered triads (chapter 6) show a strong influence of the degree of rotational restriction on the lifetimes and rate constants of the CS processes. The rate constants of CS are increasing with increasing rotational freedom. The magnetic field dependent decay data show that the exchange interactions increase with increasing rotational freedom. Based on the CR dynamics, the calculated electronic couplings of the ET processes reflect the same trend along the series. Here, only singlet couplings turned out to be strongly influenced while the triplet couplings are not. Therefore, this series shows that the ET dynamics of donor acceptor systems can strongly be influenced by restricting the rotational freedom. In the substituted triptycene triads (chapter 7), decreasing electron density in the bridging unit causes a decrease of the CS rate constants. The magnetic field dependent decay data show that with decreasing electron density in the bridge the exchange interaction decreases. The CR dynamics-based rate constants and the electronic couplings follow the same trend as the exchange interaction. This series shows that varying the HOMO/LUMO levels of the connecting bridge between donor and acceptor strongly influences the ET processes. In the anthracene bridge triads (chapter 8), the CS process is slow in both triads. The CR was fast in the anthracene triad and is slowed down in the methoxy substituted anthracene bridge triad. The increase of the exchange interaction with increasing electron density in the bridge was more pronounced than in the substituted triptycene triads. Thus, the variation of electron density in the bridge strongly influences the ET processes even though the rotation is restricted. In this thesis, it was shown that the influence of the rotational hindrance as well as the electron density in a connecting bridge have strong influence on all ET processes and the electronic coupling in donor acceptor systems. These approaches can therefore be used to modify magnetic properties of new materials.}, subject = {Rotation}, language = {en} } @article{RiethToberLimbachetal.2020, author = {Rieth, Thorsten and Tober, Natalie and Limbach, Daniel and Haspel, Tobias and Sperner, Marcel and Schupp, Niklas and Wicker, Philipp and Glang, Stefan and Lehmann, Matthias and Detert, Heiner}, title = {Impact of substitution pattern and chain length on the thermotropic properties of alkoxy-substituted triphenyl-tristriazolotriazines}, series = {Molecules}, volume = {25}, journal = {Molecules}, number = {23}, issn = {1420-3049}, doi = {10.3390/molecules25235761}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220019}, year = {2020}, abstract = {Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure-property relationships of the number of alkyl chains, their position, length and structure were studied.}, language = {en} } @phdthesis{Riese2019, author = {Riese, Stefan}, title = {Photophysics and Spin Chemistry of Donor-Acceptor substituted Dipyrrinato-Metal-Complexes}, doi = {10.25972/OPUS-18022}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-180228}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2019}, abstract = {In this thesis, the photophysics and spin chemistry of donor-photosensitizer-acceptor triads were investigated. While all investigated triads comprised a TAA as an electron donor and a NDI as an electron acceptor, the central photosensitizers (PS) were different chromophores based on the dipyrrin-motif. The purity and identity of all target compounds could be confirmed by NMR spectroscopy, mass spectrometry and elemental analysis. The first part of the work dealt with dipyrrinato-complexes of cyclometalated heavy transition metals. The successful synthesis of novel triads based on Ir(III), Pt(II) and Pd(II) was presented. The optical and electrochemical properties indicated charge separation (CS), which was confirmed by transient absorption (TA) spectroscopy. TA-spectroscopy also revealed that the process of CS is significantly slower and less efficient for the triads based on Pt(II) and Pd(II) than for the analogous Ir(III) triads. This is mostly due to a much more convoluted reaction pathway, comprising several intermediate states before the formation of the final charge separated state (CSS2). On the other hand, CSS2 exhibits long lifetimes which are dependent on the central metal ion. While the Ir(III) triads show lifetimes of about 0.5 µs in MeCN, the Pt(II) and Pd(II) analogues show lifetimes of 1.5 µs. The magnetic field effect on the charge recombination (CR) kinetics of CSS2 was investigated by magnetic field dependent ns-TA spectroscopy and could be rationalized based on a classical kinetic scheme comprising only one magnetic field dependent rate constant k±. The behavior of k± shows a clear separation of the coherent and incoherent spin interconversion mechanisms. While the coherent spin evolution is due to the isotropic hyperfine coupling with the magnetic nuclei of the radical centers, the incoherent spin relaxation is due to a rotational modulation of the anisotropic hyperfine coupling tensor and is strongly dependent on the viscosity of the solvent. This dependence could be used to measure the nanoviscosity of the oligomeric solvent pTHF, which was found to be distinctly different from its macroviscosity. The second part of the work dealt with bisdipyrrinato complexes and their bridged porphodimethenato (PDM) analogues. Initially, the suitability of the different chromophores for the use as PS in donor-acceptor substituted triads was tested by a systematic investigation of their steady state and transient properties. While the PDM-complex of Zn(II) and Pd(II) exhibited promising characteristics such as a high exited state lifetime and relatively intense emission, the purely organic parent PDM and the non-bridged bisdipyrrinato-Pd(II) complex were less suitable. The difference between the two Pd(II) complexes could be explained by a structural rearrangement of the non-bridged complex which results in a non-emissive metal centered triplet state with disphenoidal geometry. This rearrangement is prevented by the dimethylmethylene-bridges in the bridged analogue resulting in higher phosphorescence quantum yields and excited state lifetimes. With the exception of the Zn(II)PDM-complex, the synthesis of novel donor acceptor substituted triads could be realized for all desired central chromophores. They were investigated equivalently to the cyclometalated triads described in the first part. The steady state properties indicate a stronger electronic coupling between the subunits due to the lack of unsaturated bridges between the donor and the central chromophore. Photoinduced CS occurs in all investigated triads. Due to the low exited state lifetimes of the central chromophores, CSS is formed less efficiently for the triads based on the unbridged Pd(II)-complex as well as the purely organic PDM. In the triad based on the bridged Pd(II) complex, the CR of CSS2 is faster than its formation resulting in low intermediate concentrations. For its elongated analogue, this is not the case and CSS2 can be observed clearly. Although the spin-chemistry of the triads based on bisdipyrrinato-Pd(II) and porphodimethenato-Pd(II) is less well understood, first interpretations of the magnetic field dependent decay kinetics gave results approximately equivalent to those obtained for the cyclometalated triads. Furthermore, the MFE was shown to be useful for the investigation of the quantum yield of CS and the identity of the observed CSSs. In both parts of this work, the influence of the central photosensitizer on the photophysics and the spin chemistry of the triads could be shown. While the process of CS is directly dependent on the PS, the PS usually is not directly involved in the final CSSs. None the less, it can still indirectly affect the CR and spin chemistry of the CSS since it influences the electronic coupling between donor and acceptor, as well as the geometry of the triads.}, subject = {Charge-transfer-Komplexe}, language = {en} } @article{ReuterEngelsPeyerimhoff1992, author = {Reuter, W. and Engels, Bernd and Peyerimhoff, S.D.}, title = {The Reaction of Singlet and Triplet Methylen with Ethene - A Multi-Reference CI Study}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58923}, year = {1992}, abstract = {Large-scale multireference configuration interaction (MRD-CI) calculations in a flexible atomic orbital (AO) basis are employed to study the reaction of C\(_2\)H\(_4\) with CH\(_2\) in its firSt triplet and singlet state. The minimum energy path (MEP) of both reactions is calculated, and different mechanisms are discussed. To examine the possible participation of the singlet state in the overall reaction starting from the triplet channel and terminating in the singlet-state c-C\(_3\)H\(_6\), various cuts through both hypersurfaces are calculated. lt is found that favorable interconversion from the trip1et to the singlet surface can only occur at !arge separations of the two fragments of CH2 and C\(_2\)H\(_4\). Experimental data considering the vibrational motion of CH\(_2\) in connection with the relative position of both surfaces are used to obtain an estimate for the overall barrier of the reaction. The height of the barrier is about 6 kcal/mol, while the barrier of the pure triplet reaction is calculated to be 7-9 kcal/mol.}, subject = {Organische Chemie}, language = {en} } @article{RestMayoralFernandez2013, author = {Rest, Christina and Mayoral, Mar{\´i}a Jos{\´e} and Fern{\´a}ndez, Gustavo}, title = {Aqueous Self-Sorting in Extended Supramolecular Aggregates}, series = {International Journal of Molecular Sciences}, volume = {14}, journal = {International Journal of Molecular Sciences}, number = {1}, doi = {10.3390/ijms14011541}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129435}, pages = {1541-1565}, year = {2013}, abstract = {Self-organization and self-sorting processes are responsible for the regulation and control of the vast majority of biological processes that eventually sustain life on our planet. Attempts to unveil the complexity of these systems have been devoted to the investigation of the binding processes between artificial molecules, complexes or aggregates within multicomponent mixtures, which has facilitated the emergence of the field of self-sorting in the last decade. Since, artificial systems involving discrete supramolecular structures, extended supramolecular aggregates or gel-phase materials in organic solvents or—to a lesser extent—in water have been investigated. In this review, we have collected diverse strategies employed in recent years to construct extended supramolecular aggregates in water upon self-sorting of small synthetic molecules. We have made particular emphasis on co-assembly processes in binary mixtures leading to supramolecular structures of remarkable complexity and the influence of different external variables such as solvent and concentration to direct recognition or discrimination processes between these species. The comprehension of such recognition phenomena will be crucial for the organization and evolution of complex matter.}, language = {en} } @phdthesis{Rest2015, author = {Rest, Christina}, title = {Self-assembly of amphiphilic oligo(phenylene ethynylene)-based (bi)pyridine ligands and their Pt(II) and Pd(II) complexes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-133248}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {The presented work in the field of supramolecular chemistry describes the synthesis and detailed investigation of (bi)pyridine-based oligo(phenylene ethynylene) (OPE) amphiphiles, decorated with terminal glycol chains. The metal-ligating property of these molecules could be exploited to coordinate to Pd(II) and Pt(II) metal ions, respectively, resulting in the creation of novel metallosupramolecular π-amphiphiles of square-planar geometry. The focus of the presented studies is on the self-assembly behaviour of the OPE ligands and their corresponding metal complexes in polar and aqueous environment. In this way, the underlying aggregation mechanism (isodesmic or cooperative) is revealed and the influence of various factors on the self-assembly process in supramolecular systems is elucidated. In this regard, the effect of the molecular design of the ligand, the coordination to a metal centre as well as the surrounding medium, the pH value and temperature is investigated.}, subject = {Supramolekulare Chemie}, language = {en} } @article{RennerStolteWuerthner2020, author = {Renner, Rebecca and Stolte, Matthias and W{\"u}rthner, Frank}, title = {Self-Assembly of bowl-shaped naphthalimide-annulated corannulene}, series = {ChemistryOpen}, volume = {9}, journal = {ChemistryOpen}, number = {1}, doi = {10.1002/open.201900291}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204396}, pages = {32-39}, year = {2020}, abstract = {The self-assembly of a bowl-shaped naphthalimide-annulated corannulene of high solubility has been studied in a variety of solvents by NMR and UV/Vis spectroscopy. Evaluation by the anti-cooperative K\(_2\)-K model revealed the formation of supramolecular dimers of outstanding thermodynamic stability. Further structural proof for the almost exclusive formation of dimers over extended aggregates is demonstrated by atomic force microscopy (AFM) and diffusion ordered spectroscopy (DOSY) measurements as well as by theoretical calculations. Thus, herein we present the first report of a supramolecular dimer of an annulated corannulene derivative in solution and discuss its extraordinarily high thermodynamic stability with association constants up to > 10\(^6\)M\(^-\) \(^1\) in methylcyclohexane, which is comparable to the association constants given for planar phthalocyanine and perylene bisimide dyes.}, language = {en} } @article{RennerMahlmeisterAnhaltetal.2021, author = {Renner, Rebecca and Mahlmeister, Bernhard and Anhalt, Olga and Stolte, Matthias and W{\"u}rthner, Frank}, title = {Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {46}, doi = {10.1002/chem.202101877}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-249070}, pages = {11997 -- 12006}, year = {2021}, abstract = {A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol\(^{-1}\) for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol\(^{-1}\). The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.}, language = {en} } @phdthesis{Renner2021, author = {Renner, Rebecca}, title = {Aggregation, Chirality and Reduction of Nonplanar Polycyclic Aromatic Hydrocarbons}, doi = {10.25972/OPUS-24700}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-247000}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Within this thesis the interactions between novel corannulene derivatives in solution as well as in the solid state by changing the imide residue of a literature known extended corannulene dicarboximide were investigated, in order to obtain a better understanding of the packing and possible charge transport in potential applications. Accordingly, the goal of the work was to synthesize and investigate an electron-poor corannulene bis(dicarboximide) based on previously published work but with higher solubility and less steric encumbrance in imide position to enable self-assembly in solution. To obtain further insights into the conformational stability, structure and chiroptical properties of heavily twisted PBIs another aim of this thesis was the design, synthesis, and optoelectronic investigation of various fourfold directly arylated PBIs by substitution in bay position with smaller hydrocarbons with different steric demand, i.e., benzene, naphthalene and pyrene, which should be separable by chiral high performance liquid chromatography (HPLC). As of yet, no concise study concerning the optical and electronic properties of differently core-substituted PBIs in the neutral as well as the mono- and dianionic state in solution is available, which also elucidates the origin of the different optical transitions observed in the absorption and emission spectra. Thus, in this thesis, the investigation of five PBI derivatives with different frontier energetic levels to produce a reference work of reduced PBIs was tackled.}, subject = {Corannulene}, language = {en} } @phdthesis{Reitzenstein2010, author = {Reitzenstein, D{\"o}rte}, title = {Donor-Acceptor Conjugated Polymers for Application in Organic Electronic Devices}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-53939}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {In the first part of the work three polycarbazoles poly[N-((4-dimesitylboryl)-3,5-dimethylphenyl)-carbazole]-2,7-diyl P1, poly[N-((4-dimesitylboryl)-3,5-dimethylphenyl)-carbazole]-3,6-diyl P2 and poly[N-(4-(diphenylmethylene)-phenyl)- carbazole]-2,7-diyl P3 were synthesized by Yamamoto coupling reaction and their spectroscopic and electrochemical properties were investigated. Absorption and fluorescence characteristics of P1 and P3 were found to be similar to other 2,7-linked polycarbazoles, whereas P2 shows a CT absorption band arising from a shift of electron density from the nitrogen of the carbazole donor to the triarylborane acceptor. This causes a negative solvatochromic absorption and a positive solvatochromic fluorescence behaviour and is responsible for the significantly enlarged fluorescence quantum efficiency in solution and solid state compared to other 3,6-linked polycarbazoles. Thus the spectroscopic properties are governed by the connection pattern: the 2,7-linked polycarbazoles are not affected by the acceptor substituent due to the rigid poly-para-phenylene-like backbone structure, whereas the 3,6-linked polycarbazole P2 is dominated by the properties of the monomer unit due to its more flexible (less conjugated) structure. The oxidative processes of P1-P3 have been investigated in detail by cyclic voltammetry, which are similar to known 2,7- and 3,6-polycarbazoles. The reversible reduction found for P1 and P2, respectively, is attributed to the reduction of the triarylborane moiety. No reduction process referring to the carbazole moiety was observed. Due to its better solubility compared to P1 and P3 only P2 was used as active layer in an OLED device (ITO/P2/Al). The electroluminescence spectrum revealed CIE coordinates of (0.17, 0.21). In the second part of the work the low band gap polyradical poly{[((2,3,4,5,6-pentachlorophenyl)-bis(2,3,5,6-tetrachlorophenyl)methyl radical)-4,4'-diyl]-alt-4,4'-bis(vinylphenyl)-4-(2-ethylhexyloxy)phenylamin} P4 was synthesized by Horner-Emmons reaction. It shows an IV-CT band in the NIR, which arises from an ET from the triarylamine donor to the PCTM radical acceptor. This transition is confined to one monomer unit as deduced from comparison with the monomer spectra. HOMO and LUMO of P4 determined by cyclic voltammetry are at -5.5 and -4.5 eV, respectively. The smaller electrochemical band gap (1.0 eV) compared to the optical band gap (1.2 eV) is probably caused by ion pairing effects in the electrochemical experiments and indicates a low exciton binding energy. Femtosecond-pump-probe transient absorption spectroscopy revealed the spectral features of the oxidized triarylamine donor and the reduced PCTM acceptor similar to the spectra obtained separately for positive and negative potentials by spectroelectrochemistry. Thus the ET event causing the IV-CT absorption band could unambiguously be identified. The decay of the IV-CT state was found to be biexponential. The fast solvent dependent decay component is ascribed to the direct decay from the IV-CT state to the ground state, whereas the slow solvent independent decay component is tentatively attributed to an equilibrium formation of the IV-CT state and a completely charge separated state formed by charge migration along the polymer backbone. Well balanced ambipolar charge transport with hole and electron mobilities of ca. 3 × 10-5 cm2 V-1 s-1 was found in OFET devices (BG/TC structure) comprising an additional insulating organic PPcB layer. Polymer/polymer BHJ solar cell devices with the structure glass/ITO/PEDOT:PSS/(P3HT/P4)/Ca/Al yielded a power conversion efficiency of 3.1 × 10-3 \%, VOC = 0.38 V, JSC = 2.8 × 10-2 mA cm-2 and FF = 0.29 for the 1:4 (P3HT/P4) blend ratio. The improper solid state morphology of P4 that causes the unsatisfying performance of OFET and solar cell devices renders P4 less suitable for these applications, whereas the hypothesis of charge migration in the excited state is worth to be investigated in more detail.}, subject = {Carbazolderivate}, language = {en} } @phdthesis{Rehm2008, author = {Rehm, Thomas Helge}, title = {A Guide to Supramolecular Assemblies in Polar Solutions - From Nanometre-Sized Cyclic Dimers to Large Vesicular Structures}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28359}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {This PhD thesis introduced several concepts for the construction of new supramolecular assem-blies in polar solvents. Although the building blocks differ in their binding mode and association strength they follow the same principle: one main driving force for the self-assembly in polar solutions in combination with one texturing force. The main self-assembly process is based on the mutual interaction of hydrogen-bond enforced ion pairs which deliver the association energy needed for stable, supramolecular structures even in polar solvents. The texturing force itself is represented by the linkers between the zwitterionic building blocks or parts of them. The different length and functionalization of the linkers have a tremendous influence on the mode of self-assembly leading to cyclic dimers, vesicles, layers or solid spheres. Hence, this principle is suitable for the construction of programmable monomers. Since the derivatisation of the main binding motive is rather simple it offers a great number of new and undoubtedly fascinating structures with potential applications in material and biomimetic science.}, subject = {Supramolekulare Chemie}, language = {en} } @phdthesis{Rehm2015, author = {Rehm, Stefanie}, title = {Spermine-functionalized Perylene Bisimide Dyes: Synthesis and Self-assembly in Water}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-123201}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {The main objective of this thesis was the design and synthesis of perylene bisimide dyes with sufficient water-solubility for the construction of self-assembled architectures in aqueous solutions. Beside these tasks another goal of this project was the control over the self-assembly process in terms of aggregate size and helicity, respectively. Within this thesis an appropriate synthesis for spermine-functionalized perylene bisimide dyes was developed and conducted successfully. The characterization of these building blocks and their course of self-assembly were investigated by NMR, UV/Vis and fluorescence spectroscopy as well as by atomic force and transmission electron microscopy. For the better understanding of the experimental results theoretical calculations were performed.}, subject = {Perylenderivate}, language = {en} } @article{Ravat2021, author = {Ravat, Prince}, title = {Carbo[n]helicenes Restricted to Enantiomerize: An Insight into the Design Process of Configurationally Stable Functional Chiral PAHs}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {12}, doi = {10.1002/chem.202004488}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225871}, pages = {3957 -- 3967}, year = {2021}, abstract = {The most important stereodynamic feature of carbo[n]helicenes is the interconversion of their enantiomers. The Gibbs activation energy (ΔG≠(T)) of this process, which determines the rate of enantiomerization, dictates the configurational stability of [n]helicenes. High values of ΔG≠(T) are required for applications of functional chiral molecules incorporating [n]helicenes or helicene substructures. This minireview provides an overview of the mechanism, recent developments, and factors affecting the enantiomerization of [n]helicenes, which will accelerate the design process of configurationally stable functional chiral molecules based on helicene substructures. Additionally, this minireview addresses the misconception and irregularities in the recent literature on how the terms "racemization" and "enantiomerization" are used as well as how the activation parameters are calculated for [n]helicenes and related compounds.}, language = {en} } @phdthesis{Rausch2021, author = {Rausch, Rodger}, title = {Chemistry of Chromophore Bridged Biradicals - Synthesis and Properties}, doi = {10.25972/OPUS-22650}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226501}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Within this PhD thesis, chromophore-bridged biradicals were synthesised and their properties characterised. Therefore, it was necessary to develop novel synthetic procedures and implement several experimental characterisation methods. In summary, within this thesis the scope of pigment chromophore phenoxyl radical decoration was further explored and expanded to IIn as well as DPP colourants. HOMA analysis highlighted the importance of aromaticity in order to understand the spin crossover from heteroaromatic quinoidal to aromatic open shell DPPs. Finally, PBI, IIn and DPP biradicals were advanced towards stable materials by introduction of nitronyl nitroxide radical centres.}, subject = {Biradikal}, language = {en} } @article{RagerJakowetzGoleetal.2019, author = {Rager, Sabrina and Jakowetz, Andreas C. and Gole, Bappaditya and Beuerle, Florian and Medina, Dana D. and Bein, Thomas}, title = {Scaffold-Induced Diketopyrrolopyrrole Molecular Stacks in a Covalent Organic Framework}, series = {Chemistry of Materials}, volume = {31}, journal = {Chemistry of Materials}, number = {8}, doi = {10.1021/acs.chemmater.8b02882}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224927}, pages = {2707-2712}, year = {2019}, abstract = {In recent years, covalent organic frameworks (COFs) have attracted considerable attention due to their crystalline and porous nature, which positions them as intriguing candidates for diverse applications such as catalysis, sensing, or optoelectronics. The incorporation of dyes or semiconducting moieties into a rigid two-dimensional COF can offer emergent features such as enhanced light harvesting or charge transport. However, this approach can be challenging when dealing with dye molecules that exhibit a large aromatic backbone, since the steric demand of solubilizing side chains also needs to be integrated into the framework. Here, we report the successful synthesis of DPP2-HHTP-COF consisting of diketopyrrolopyrrole (DPP) diboronic acid and hexahydroxytriphenylene (HHTP) building blocks. The well-known boronate ester coupling motif guides the formation of a planar and rigid backbone and long-range molecular DPP stacks, resulting in a highly crystalline and porous material. DPP2-HHTP-COF exhibits excellent optical properties including strong absorption over the visible spectral range, broad emission into the NIR and a singlet lifetime of over 5 ns attributed to the formation of molecular stacks with J-type interactions between the DPP subcomponents in the COF. Electrical measurements of crystalline DPP2-HHTP-COF pellets revealed conductivity values of up to 10(-6) S cm(-1).}, language = {en} } @article{QuastGescheidtSpichty2020, author = {Quast, Helmut and Gescheidt, Georg and Spichty, Martin}, title = {Topological dynamics of a radical ion pair: Experimental and computational assessment at the relevant nanosecond timescale}, series = {Chemistry}, volume = {2}, journal = {Chemistry}, number = {2}, issn = {2624-8549}, doi = {10.3390/chemistry2020014}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-285195}, pages = {219 -- 230}, year = {2020}, abstract = {Chemical processes mostly happen in fluid environments where reaction partners encounter via diffusion. The bimolecular encounters take place at a nanosecond time scale. The chemical environment (e.g., solvent molecules, (counter)ions) has a decisive influence on the reactivity as it determines the contact time between two molecules and affects the energetics. For understanding reactivity at an atomic level and at the appropriate dynamic time scale, it is crucial to combine matching experimental and theoretical data. Here, we have utilized all-atom molecular-dynamics simulations for accessing the key time scale (nanoseconds) using a QM/MM-Hamiltonian. Ion pairs consisting of a radical ion and its counterion are ideal systems to assess the theoretical predictions because they reflect dynamics at an appropriate time scale when studied by temperature-dependent EPR spectroscopy. We have investigated a diketone radical anion with its tetra-ethylammonium counterion. We have established a funnel-like transition path connecting two (equivalent) complexation sites. The agreement between the molecular-dynamics simulation and the experimental data presents a new paradigm for ion-ion interactions. This study exemplarily demonstrates the impact of the molecular environment on the topological states of reaction intermediates and how these states can be consistently elucidated through the combination of theory and experiment. We anticipate that our findings will contribute to the prediction of bimolecular transformations in the condensed phase with relevance to chemical synthesis, polymers, and biological activity.}, language = {en} } @phdthesis{Qamar2012, author = {Qamar, Riaz-ul}, title = {Synthesis of functionalized molecular probes for bioorthogonal metabolic glycoengineering}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-73378}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2012}, abstract = {Biomolecules are difficult to investigate in their native environment. The vast complexity of cellular systems and seldom availability of chemical reactions compatible with the physiological milieu make it a challenging task. Bioorthogonal chemical reactions serve as a key to achieve selective ligation, whose components must react rapidly and selectively with each other under physiological conditions in the presence of the plethora of functionalities necessary to sustain life. In this dissertation, we focused on the synthesis of chemical reporters and probe molecules for bioorthogonal labeling through click reaction. Initially, sialic acid derivatives with a linker containing terminal alkyne functionality were synthesized. After the synthesis of azide derivatives of fluorescent dyes as counter partners, they were conjugated with sialic acids through Cu(I) catalyzed alkyne azide cycloaddition (CuAAC). The successful in vitro conjugation of Sia and fluorescent dyes was followed by metabolic tagging of human larynx carcinoma (HEp-2) and the carcinoma of Chinese hamster ovary (CHO­K1) with alkynated Sia that were subsequently ligated with fluorescein azide. Finally, the stained cells were subjected to fluorescent microscopy to obtain their images. To enable the click reaction compatible to in vivo applications, the reactivity of cyclooctyne was enhanced by two different approaches. In a first approach, following the Bertozzi's strategy, two fluorine atoms were introduced adjacent to the alkyne to lower the LUMO. In a second strategy the ring strain of cyclooctyne was attempted to be enhanced by the introduction of an amide group. In addition, glutarimide derivatives with free amino and carboxylic acid functional groups were synthesized by domino-Michael addition-cyclization-reaction.}, subject = {Click-Chemie}, language = {en} } @article{PoepplerLuebtowSchlauersbachetal.2019, author = {P{\"o}ppler, Ann-Christin and L{\"u}btow, Michael M. and Schlauersbach, Jonas and Wiest, Johannes and Meinel, Lorenz and Luxenhofer, Robert}, title = {Loading dependent Structural Model of Polymeric Micelles Encapsulating Curcumin by Solid-State NMR Spectroscopy}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {51}, doi = {10.1002/anie.201908914}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206705}, pages = {18540-18546}, year = {2019}, abstract = {Detailed insight into the internal structure of drug-loaded polymeric micelles is scarce, but important for developing optimized delivery systems. We observed that an increase in the curcumin loading of triblock copolymers based on poly(2-oxazolines) and poly(2-oxazines) results in poorer dissolution properties. Using solid-state NMR spectroscopy and complementary tools we propose a loading-dependent structural model on the molecular level that provides an explanation for these pronounced differences. Changes in the chemical shifts and cross-peaks in 2D NMR experiments give evidence for the involvement of the hydrophobic polymer block in the curcumin coordination at low loadings, while at higher loadings an increase in the interaction with the hydrophilic polymer blocks is observed. The involvement of the hydrophilic compartment may be critical for ultrahigh-loaded polymer micelles and can help to rationalize specific polymer modifications to improve the performance of similar drug delivery systems.}, language = {en} }