@article{MessiNdjokoIosetHertleinAmslingeretal.2012, author = {Messi, Bernadette Biloa and Ndjoko-Ioset, Karine and Hertlein-Amslinger, Barbara and Lannang, Alain Meli and Nkengfack, Augustin E. and Wolfender, Jean-Luc and Hostettmann, Kurt and Bringmann, Gerhard}, title = {Preussianone, a New Flavanone-Chromone Biflavonoid from Garcinia preussii Engl.}, series = {Molecules}, volume = {17}, journal = {Molecules}, number = {5}, doi = {10.3390/molecules17056114}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-130881}, pages = {6114 - 6125}, year = {2012}, abstract = {A new flavanone-chromone biflavonoid, preussianone (1), has been isolated from the leaves of Garcinia preussii, along with four known biflavonoids. The absolute stereostructures were elucidated by chemical, spectroscopic, and chiroptical methods. The biological properties of the new biflavonoid against several bacterial strains were evaluated.}, language = {en} } @article{MerzMerzKirchneretal.2021, author = {Merz, Viktor and Merz, Julia and Kirchner, Maximilian and Lenhart, Julian and Marder, Todd B. and Krueger, Anke}, title = {Pyrene-Based "Turn-Off" Probe with Broad Detection Range for Cu\(^{2+}\), Pb\(^{2+}\) and Hg\(^{2+}\) Ions}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {31}, doi = {10.1002/chem.202100594}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256803}, pages = {8118-8126}, year = {2021}, abstract = {Detection of metals in different environments with high selectivity and specificity is one of the prerequisites of the fight against environmental pollution with these elements. Pyrenes are well suited for the fluorescence sensing in different media. The applied sensing principle typically relies on the formation of intra- and intermolecular excimers, which is however limiting the sensitivity range due to masking of e. g. quenching effects by the excimer emission. Herein we report a highly selective, structurally rigid chemical sensor based on the monomer fluorescence of pyrene moieties bearing triazole groups. This sensor can quantitatively detect Cu\(^{2+}\), Pb\(^{2+}\) and Hg\(^{2+}\) in organic solvents over a broad concentrations range, even in the presence of ubiquitous ions such as Na\(^{+}\), K\(^{+}\), Ca\(^{2+}\) and Mg\(^{2+}\). The strongly emissive sensor's fluorescence with a long lifetime of 165 ns is quenched by a 1 : 1 complex formation upon addition of metal ions in acetonitrile. Upon addition of a tenfold excess of the metal ion to the sensor, agglomerates with a diameter of about 3 nm are formed. Due to complex interactions in the system, conventional linear correlations are not observed for all concentrations. Therefore, a critical comparison between the conventional Job plot interpretation, the method of Benesi-Hildebrand, and a non-linear fit is presented. The reported system enables the specific and robust sensing of medically and environmentally relevant ions in the health-relevant nM range and could be used e. g. for the monitoring of the respective ions in waste streams.}, language = {en} } @phdthesis{Merz2022, author = {Merz, Viktor}, title = {Funktionalisierung und Untersuchung von Nanodiamanten f{\"u}r biomedizinische und sensorische Anwendungen}, doi = {10.25972/OPUS-24588}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-245888}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {Nanodiamant (ND) ist ein vielseitiges und vielversprechendes Material f{\"u}r Bio-Anwendungen. Trotz vieler Bem{\"u}hungen bleibt die Agglomeration von Nanodiamant und die unspezifische Adsorption von Proteinen an der ND-Oberfl{\"a}che bei Kontakt mit Biofl{\"u}ssigkeiten ein großes Hindernis f{\"u}r biomedizinische Anwendungen. Eine Auswahl verzweigter und linearer Molek{\"u}le mit {\"u}berlegener F{\"a}higkeit zur kolloidalen Stabilisierung von Nanopartikeln in Salz- und Zellmedienumgebung, f{\"u}r bis zu 30 Tage, wurde an die ND-Oberfl{\"a}che angebracht. Das Baukastensystem mit Azid als Außengruppen bietet eine große Vielfalt an Bindungen mit vielen Molek{\"u}len, wie z. B. Medikamenten, Farbstoffen oder Targeting-Molek{\"u}len. Das Anh{\"a}ngen von z. B. Zwitterionen an die Kette sch{\"u}tzt die ND-Oberfl{\"a}che vor der Bildung einer Proteinkorona, wenn die Partikel mit proteinhaltigen Biofl{\"u}ssigkeiten in Kontakt kommen. Die Ergebnisse der thermogravimetrischen Analyse der Beladung der ND-Oberfl{\"a}che zeigen eine signifikante Verhinderung der Proteinadsorption von bis zu 98 \% im Vergleich zu NDs ohne zwitterionische Kopfgruppen und eine lange kolloidale Stabilit{\"a}t, wenn Tetraethylenglykol (TEG) an die Oberfl{\"a}che gebunden wird. Die Vielseitigkeit des modularen Systems, um nicht nur zwitterionische Ketten, sondern auch klickbare funktionelle Molek{\"u}le an fluoreszierende Nanodiamanten (fNDs) zu binden, zeigt das Potenzial des Systems am Nanodiamanten. Unter Verwendung von Defektstrukturen, wie Stickstoff-Vakanz-Zentren (NV), k{\"o}nnen Diamantpartikel aufgrund ihres weitgehend ungiftigen Verhaltens als fluoreszierende Nanodiamanten (fNDs) f{\"u}r photostabile Markierung, Bioimaging und nanoskalige Sensorik in lebenden Zellen und Organismen verwendet werden. Um die fND-Oberfl{\"a}che zu funktionalisieren, wurde eine neuartige Mahltechnik mit Diazoniumsalzen etabliert, um ein Pfropfen auf wenig reaktive HPHT-fNDs durchzuf{\"u}hren, was zu einer hohen Oberfl{\"a}chenbeladung und einem hohen negativen Zetapotenzial f{\"u}hrt. Die Kombination der Vorteile von TEG und zwitterionhaltigen Gruppen mit der F{\"a}higkeit zum Targeting von Antik{\"o}rpern auf fND best{\"a}tigt zum ersten Mal die verbesserte kolloidale Stabilit{\"a}t in Experimenten mit lebenden Zellen. Dar{\"u}ber hinaus deuten die Ergebnisse auf eine verbesserte Corona-Abstoßung im Vergleich zu fND ohne zwitterionhaltige Kopfgruppen hin. Infolgedessen wurden die Zirkulationszeiten von 4 (fND ohne Zwitterionenkette, aber mit Antik{\"o}rper) auf 17 (mit Antik{\"o}rper und Zwitterionenketten) Stunden vergr{\"o}ßert. In nicht-biomedizinischen Anwendungen kann das modulare System als Sonde f{\"u}r Schwermetalle durch die Anbindung von Farbstoffen verwendet werden. Die Detektion von Metallen in verschiedenen Umgebungen mit hoher Selektivit{\"a}t und Spezifit{\"a}t ist eine der Voraussetzungen f{\"u}r den Kampf gegen die Umweltverschmutzung mit diesen Elementen. Pyrene sind gut geeignet und weit bekannt f{\"u}r die Fluoreszenzsensorik in verschiedenen Medien. Das angewandte Sensorprinzip beruht typischerweise auf der Bildung von intra- und intermolekularen Excimeren, was jedoch den Empfindlichkeitsbereich aufgrund der Maskierung von z.B. Quenching-Effekten durch die Excimer-Emission einschr{\"a}nkt. Diese Studie zeigt einen hochselektiven, strukturstabilen chemischen Sensor, der auf der monomeren Fluoreszenz von Pyrenanteilen mit Triazolgruppen basiert. Dieser Sensor kann Cu2+, Pb2+ und Hg2+ in organischen L{\"o}sungsmitteln {\"u}ber einen weiten Konzentrationsbereich quantitativ nachweisen, auch in Gegenwart von ubiquit{\"a}ren Ionen wie Na+, K+, Ca2+ und Mg2+. Die stark emittierende Fluoreszenz des Sensors mit einer langen Lebensdauer von 165 ns wird durch eine 1:1-Komplexbildung bei Zugabe von Metallionen in Acetonitril gel{\"o}scht. Bei Zugabe eines zehnfachen {\"U}berschusses des Metallions zum Sensor bilden sich Agglomerate mit einem Durchmesser von etwa 3 nm. Aufgrund der komplexen Wechselwirkungen im System werden konventionelle lineare Korrelationen nicht f{\"u}r alle Konzentrationen beobachtet. Daher wird ein kritischer Vergleich zwischen der konventionellen Job-Plot-Interpretation, der Methode von Benesi-Hildebrand und einem nicht-linearen Fit vorgestellt. Das vorgestellte System erm{\"o}glicht die spezifische und robuste Erfassung von medizinisch und {\"o}kologisch relevanten Ionen im gesundheitsrelevanten nM-Bereich und k{\"o}nnte z. B. zur {\"U}berwachung der entsprechenden Ionen in Abfallstr{\"o}men eingesetzt werden. Doch h{\"a}ufig landen diese Abfallstr{\"o}me in empfindlichen Aquakulturen, wo eine solche Sensortechnik nur funktioniert, wenn die Sonde wasserl{\"o}slich ist, um die Ausbreitung und Bildung von Umweltsch{\"a}den durch Schwermetalle zu {\"u}berwachen. Viele Chemosensoren arbeiten nur in bestimmten L{\"o}sungsmitteln und unter hochreinen Bedingungen quantitativ. In dieser Arbeit wird eine Methode zur Stabilisierung von wasserunl{\"o}slichen Chemosensoren auf Nanodiamanten in salzhaltigem Wasser unter Beibehaltung der Sensoreffektivit{\"a}t und -spezifit{\"a}t sowie der kolloidalen Stabilit{\"a}t vorgestellt. Zus{\"a}tzlich wird die Sensorf{\"a}higkeit in organischen L{\"o}sungsmitteln beibehalten. Diese Studie gibt Einblick in die Absorptionsf{\"a}higkeit von Pyren-Derivaten an der Nanodiamant-Oberfl{\"a}che und einen Weg, diese reversibel zu desorbieren. Außerdem beweist das System, dass in Anwesenheit von 95 \% Sauerstoffatmosph{\"a}re bei der Fluoreszenzmessung die Ergebnisse nicht von denen in Argonatmosph{\"a}re abweichen. Dar{\"u}ber hinaus st{\"o}rt das Vorhandensein g{\"a}ngiger Ionen im Wasser die kolloidale Stabilit{\"a}t der NDs nicht und hat auch keinen Einfluss auf die Sensorfunktionalit{\"a}t und ist somit ein vielversprechender Kandidat f{\"u}r Messungen ohne aufw{\"a}ndige Pr{\"a}parationsschritte.}, language = {en} } @article{MerzDietzVonhausenetal.2020, author = {Merz, Julia and Dietz, Maximilian and Vonhausen, Yvonne and W{\"o}ber, Frederik and Friedrich, Alexandra and Sieh, Daniel and Krummenacher, Ivo and Braunschweig, Holger and Moos, Michael and Holzapfel, Marco and Lambert, Christoph and Marder, Todd B.}, title = {Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {2}, doi = {10.1002/chem.201904219}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-207486}, pages = {438-453}, year = {2020}, abstract = {We synthesized new pyrene derivatives with strong bis(para -methoxyphenyl)amine donors at the 2,7-positions and n -azaacene acceptors at the K-region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700 nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100 ns for the new compounds, which is typical for 2,7-substituted pyrenes but not for K-region substituted pyrenes. The incorporation of strong donors and acceptors leads to very low reduction and oxidation potentials, and spectroelectrochemical studies show that the compounds are on the borderline between localized Robin-Day class-II and delocalized Robin-Day class-III species.}, language = {en} } @article{MerzDietrichNitschetal.2020, author = {Merz, Julia and Dietrich, Lena and Nitsch, J{\"o}rn and Krummenacher, Ivo and Braunschweig, Holger and Moos, Michael and Mims, David and Lambert, Christoph and Marder, Todd B.}, title = {Synthesis, Photophysical and Electronic Properties of Mono-, Di-, and Tri-Amino-Substituted Ortho-Perylenes, and Comparison to the Tetra-Substituted Derivative}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {52}, doi = {10.1002/chem.202001475}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217835}, pages = {12050 -- 12059}, year = {2020}, abstract = {We synthesized a series of new mono-, di-, tri- and tetra-substituted perylene derivatives with strong bis(para-methoxyphenyl)amine (DPA) donors at the uncommon 2,5,8,11-positions. The properties of our new donor-substituted perylenes were studied in detail to establish a structure-property relationship. Interesting trends and unusual properties are observed for this series of new perylene derivatives, such as a decreasing charge transfer (CT) character with increasing number of DPA moieties and individual reversible oxidations for each DPA moiety. Thus, (DPA)-Per possesses one reversible oxidation while (DPA)\(_{4}\)-Per has four. The mono- and di-substituted derivatives display unusually large Stokes shifts not previously reported for perylenes. Furthermore, transient absorption measurements of the new derivatives reveal an excited state with lifetimes of several hundred microseconds, which sensitizes singlet oxygen with quantum yields of up to 0.83.}, language = {en} } @phdthesis{Menekşe2023, author = {Menek{\c{s}}e, Kaan}, title = {Fabrication of Organic Solar Cells, Screening of Non-Fullerene Acceptors and the Investigation of their Intermolecular Interactions}, doi = {10.25972/OPUS-29112}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-291124}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {In this thesis, intermolecular acceptor-acceptor interactions in organic solar cells based on new non-fullerene acceptors are addressed. For this purpose, first the reproducibility of organic electronic devices was tested on a new facility for their fabrication. This was followed by the screening for new acceptor materials. Based on this, three molecular systems were investigated with regard to their acceptor-acceptor interactions and their influence on solar cell efficiency.}, subject = {Organische Solarzelle}, language = {en} } @article{MenekseRennerMahlmeisteretal.2020, author = {Menekse, Kaan and Renner, Rebecca and Mahlmeister, Bernhard and Stolte, Matthias and W{\"u}rthner, Frank}, title = {Bowl-shaped naphthalimide-annulated corannulene as nonfullerene acceptor in organic solar cells}, series = {Organic Materials}, volume = {2}, journal = {Organic Materials}, number = {3}, issn = {2625-1825}, doi = {10.1055/s-0040-1714283}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-299095}, pages = {229-234}, year = {2020}, abstract = {An electron-poor bowl-shaped naphthalimide-annulated corannulene with branched alkyl residues in the imide position was synthesized by a palladium-catalyzed cross-coupling annulation sequence. This dipolar compound exhibits strong absorption in the visible range along with a low-lying LUMO level at -3.85 eV, enabling n-type charge transport in organic thin-film transistors. Furthermore, we processed inverted bulk-heterojunction solar cells in combination with the two donor polymers PCE-10 and PM6 to achieve open-circuit voltages up to 1.04 V. By using a blend of the self-assembled naphthalimide-annulated corannulene and PCE-10, we were able to obtain a power conversion efficiency of up to 2.1\%, which is to the best of our knowledge the highest reported value for a corannulene-based organic solar cell to date.}, language = {en} } @article{MenekseMahlAlbertetal.2023, author = {Menekse, Kaan and Mahl, Magnus and Albert, Julius and Niyas, M. A. and Shoyama, Kazutaka and Stolte, Matthias and W{\"u}rthner, Frank}, title = {Supramolecularly Engineered Bulk-Heterojunction Solar Cells with Self-Assembled Non-Fullerene Nanographene Tetraimide Acceptors}, series = {Solar RRL}, volume = {7}, journal = {Solar RRL}, number = {2}, doi = {10.1002/solr.202200895}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312099}, year = {2023}, abstract = {A series of novel imide-functionalized C\(_{64}\) nanographenes is investigated as acceptor components in organic solar cells (OSCs) in combination with donor polymer PM6. These electron-poor molecules either prevail as a monomer or self-assemble into dimers in the OSC active layer depending on the chosen imide substituents. This allows for the controlled stacking of electron-poor and electron-rich π-scaffolds to establish a novel class of non-fullerene acceptor materials to tailor the bulk-heterojunction morphology of the OSCs. The best performance is observed for derivatives that are able to self-assemble into dimers, reaching power conversion efficiencies of up to 7.1\%.}, language = {en} } @article{MarkgrafCortDavisetal.1991, author = {Markgraf, J. H. and Cort, J. R. and Davis, H. A. and Lindeman, N. I. and Myers, C. R. and Kraft, A. and Christl, Manfred}, title = {Strained Heterocyclic Systems. 20. Basicities of Bicyclic Quinoxalines}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58584}, year = {1991}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} } @phdthesis{Maksimenka2010, author = {Maksimenka, Katsiaryna}, title = {Absolute Configuration by Circular Dichroism: Quantum Chemical CD Calculations}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-56552}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {Quantum chemical calculations of circular dichroism (CD) spectra in combination with experimental CD studies are one of the most efficient analytical tools for the elucidation of the three-dimensional structure of a chiral molecule. In the present work 18 chiral compounds of most different molecular structures and origins were investigated using various theoretical methods (the semiempirical CIS methods, the time-dependent DFT and DFT/MRCI approaches). The advantages and limitations of the applied methods were discussed in the context of the studied compounds. Furthermore, the last part of this work deals with the CD investigations of a chiral compound in the crystalline state. A well-known natural product with a specific conformation/CD spectrum behavior was used as a model compound to examine a novel solid-state CD method and to investigate the possibility of its improvement to provide a higher reliability for the assignment of the absolute configuration.}, subject = {Circular-Dichroismus}, language = {en} } @phdthesis{Mahlmeister2023, author = {Mahlmeister, Bernhard}, title = {Twisted Rylene Bisimides for Organic Solar Cells and Strong Chiroptical Response in the Near Infrared}, doi = {10.25972/OPUS-34610}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-346106}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {The chirality of the interlocked bay-arylated perylene motif is investigated upon its material prospect and the enhancement of its chiroptical response to the NIR spectral region. A considerable molecular library of inherently chiral perylene bisimides (PBIs) was utilized as acceptors in organic solar cells to provide decent device performances and insights into the structure-property relationship of PBI materials within a polymer blend. For the first time in the family of core-twisted PBIs, the effects of enantiopurity on the device performance was thoroughly investigated. The extraordinary structural sensitivity of CD spectroscopy served as crucial analytical tool to bridge the highly challenging gap between molecular properties and device analytics by proving the excitonic chirality of a helical PBI dimer. The chirality of this perylene motif could be further enhanced on a molecular level by both the expansion and the enhanced twisting of the π-scaffold to achieve a desirable strong chiroptical NIR response introducing a new family of twisted QBI-based nanoribbons. These achievements could be substantially further developed by expanding this molecular concept to a supramolecular level. The geometrically demanding supramolecular arrangement necessary for the efficient excitonic coupling was carefully encoded into the molecular design. Accordingly, the QBIs could form the first J-type aggregate constituting a fourfold-stranded superhelix of a rylene bisimide with strong excitonic chirality. Therefore, this thesis has highlighted the mutual corroboration of experimental and theoretical data from the molecular to the supramolecular level. It has demonstrated that for rylene bisimide dyes, the excitonic contribution to the overall chiroptical response can be designed and rationalized. This can help to pave the way for new organic functional materials to be used for chiral sensing or chiral organic light-emitting devices.}, subject = {Molek{\"u}l}, language = {en} } @article{MahlShoyamaKrauseetal.2020, author = {Mahl, Magnus and Shoyama, Kazutaka and Krause, Ana-Maria and Schmidt, David and W{\"u}rthner, Frank}, title = {Base-Assisted Imidization: A Synthetic Method for the Introduction of Bulky Imide Substituents to Control Packing and Optical Properties of Naphthalene and Perylene Imides}, series = {Angewandte Chemie International Edition}, volume = {59}, journal = {Angewandte Chemie International Edition}, number = {32}, doi = {10.1002/anie.202004965}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218246}, pages = {13401 -- 13405}, year = {2020}, abstract = {We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho,ortho-diaryl- and ortho,ortho-dialkynylaniline derivatives. This imidization method uses n-butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single-crystal X-ray diffraction analyses reveal dimeric packing motifs for monoimides, while two-side shielded bisimides crystallize in isolated molecules without close π-π-interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state.}, language = {en} } @phdthesis{Mahl2023, author = {Mahl, Magnus}, title = {Polycyclic Aromatic Dicarboximides as NIR Chromophores, Solid-State Emitters and Supramolecular Host Platforms}, doi = {10.25972/OPUS-23462}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234623}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {The present thesis introduce different synthetic strategies towards a variety of polycyclic aromatic dicarboximides (PADIs) with highly interesting and diverse properties. This included tetrachlorinated, tetraaryloxy- and tetraaryl-substituted dicarboximides, fused acceptor‒donor(‒acceptor) structures as well as sterically shielded rylene and nanographene dicarboximides. The properties and thus the disclosure of structure‒property relationships of the resulting dyes were investigated in detail among others with UV‒vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry and single crystal X-ray analysis. For instance, some of the fused and substituted PADIs offer strong absorption of visible and near infrared (NIR) light, NIR emission and low-lying LUMO levels. On the contrary, intriguing optical features in the solid-state characterize the rylene dicarboximides with their bulky N-substituents, while the devised sterically enwrapped nanographene host offered remarkable complexation capabilities in solution.}, subject = {Organische Chemie}, language = {en} } @unpublished{MaghamiScheitlHoebartner2019, author = {Maghami, Mohammad Ghaem and Scheitl, Carolin P. M. and H{\"o}bartner, Claudia}, title = {Direct in vitro selection of trans-acting ribozymes for posttranscriptional, site-specific, and covalent fluorescent labeling of RNA}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.9b10531}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192333}, year = {2019}, abstract = {General and efficient tools for site-specific fluorescent or bioorthogonal labeling of RNA are in high demand. Here, we report direct in vitro selection, characterization, and application of versatile trans-acting 2'-5' adenylyl transferase ribozymes for covalent and site-specific RNA labeling. The design of our partially structured RNA pool allowed for in vitro evolution of ribozymes that modify a predetermined nucleotide in cis (i.e. intramolecular reaction), and were then easily engineered for applications in trans (i.e. in an intermolecular setup). The resulting ribozymes are readily designed for specific target sites in small and large RNAs and accept a wide variety of N6-modified ATP analogues as small molecule substrates. The most efficient new ribozyme (FH14) shows excellent specificity towards its target sequence also in the context of total cellular RNA.}, language = {en} } @article{MaghamiDeyLenzetal.2020, author = {Maghami, Mohammad Ghaem and Dey, Surjendu and Lenz, Ann-Kathrin and H{\"o}bartner, Claudia}, title = {Repurpsing Antiviral Drugs for Orthogonal RNA-Catalyzed Labeling}, series = {Angewandte Chemie, International Edition}, volume = {59}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.202001300}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-205552}, pages = {9335-9339}, year = {2020}, abstract = {In vitro selected ribozymes are promising tools for site-specific labeling of RNA. Previously known nucleic acid catalysts attached fluorescently labeled adenosine or guanosine derivatives through 2',5'-branched phosphodiester bonds to the RNA of interest. Herein, we report new ribozymes that use orthogonal substrates, derived from the antiviral drug tenofovir, and attach bioorthogonal functional groups, as well as affinity handles and fluorescent reporter units through a hydrolytically more stable phosphonate ester linkage. The tenofovir transferase ribozymes were identified by in vitro selection and are orthogonal to nucleotide transferase ribozymes. As genetically encodable functional RNAs, these ribozymes may be developed for potential cellular applications. The orthogonal ribozymes addressed desired target sites in large RNAs in vitro, as shown by fluorescent labeling of E. coli 16S and 23S RNAs in total cellular RNA.}, language = {en} } @article{LuebtowMarciniakSchmiedeletal.2019, author = {L{\"u}btow, Michael M. and Marciniak, Henning and Schmiedel, Alexander and Roos, Markus and Lambert, Christoph and Luxenhofer, Robert}, title = {Ultra-high to ultra-low drug loaded micelles: Probing host-guest interactions by fluorescence spectroscopy}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {54}, doi = {10.1002/chem.201902619}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206128}, pages = {12601-12610}, year = {2019}, abstract = {Polymer micelles are an attractive means to solubilize water insoluble compounds such as drugs. Drug loading, formulations stability and control over drug release are crucial factors for drug-loaded polymer micelles. The interactions between the polymeric host and the guest molecules are considered critical to control these factors but typically barely understood. Here, we compare two isomeric polymer micelles, one of which enables ultra-high curcumin loading exceeding 50 wt.\%, while the other allows a drug loading of only 25 wt.\%. In the low capacity micelles, steady-state fluorescence revealed a very unusual feature of curcumin fluorescence, a high energy emission at 510 nm. Time-resolved fluorescence upconversion showed that the fluorescence life time of the corresponding species is too short in the high-capacity micelles, preventing an observable emission in steady-state. Therefore, contrary to common perception, stronger interactions between host and guest can be detrimental to the drug loading in polymer micelles.}, subject = {Polymer-drug interaction}, language = {en} } @phdthesis{Lohr2008, author = {Lohr, Andreas}, title = {Self-Assembly of Merocyanines : Thermodynamic and Kinetic Insights into the Formation of Well-Defined Dye Aggregates}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28964}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {The present thesis demonstrates the potential of dipolar aggregation of merocyanine dyes as novel directional and specific supramolecular binding motif for the creation of more elaborate supramolecular architectures beyond simple dimers. Furthermore, the self-assembly studies into bis(merocyanine) nanorods gave new insights into the kinetics of morphogenesis in supramolecular aggregates.}, subject = {Supramolekulare Chemie}, language = {en} } @article{LiuVonhausenSchulzetal.2022, author = {Liu, Bin and Vonhausen, Yvonne and Schulz, Alexander and H{\"o}bartner, Claudia and W{\"u}rthner, Frank}, title = {Peptide Backbone Directed Self-Assembly of Merocyanine Oligomers into Duplex Structures}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {21}, doi = {10.1002/anie.202200120}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318797}, year = {2022}, abstract = {The pseudopeptide backbone provided by N-(2-aminoethyl)-glycine oligomers with attached nucleobases has been widely utilized in peptide nucleic acids (PNAs) as DNA mimics. Here we demonstrate the suitability of this backbone for the formation of structurally defined dye stacks. Toward this goal a series of peptide merocyanine (PMC) dye oligomers connected to a N-(2-aminoethyl)-glycine backbone were prepared through peptide synthesis. Our concentration-, temperature- and solvent-dependent UV/Vis absorption studies show that under the control of dipole-dipole interactions, smaller-sized oligomers consisting of one, two or three dyes self-assemble into defined duplex structures containing two up to six chromophores. In contrast, upon further extension of the oligomer, the chosen peptide backbone cannot direct the formation of a defined duplex architecture anymore due to intramolecular aggregation between the dyes. For all aggregate species a moderate aggregation-induced emission enhancement is observed.}, language = {en} } @phdthesis{Liess2017, author = {Liess, Andreas}, title = {Structure-Property Relationships of Merocyanine Dyes in the Solid State: Charge Transport and Exciton Coupling}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-152900}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2017}, abstract = {The present thesis demonstrates the importance of the solid state packing of dipolar merocyanine dyes with regard to charge transport and exciton coupling. Due to the charge transport theory for disordered materials, it is expected that high ground state dipole moments in amorphous thin films lead to low mobility values due to a broadening of the density of states. However, due to their inherent dipolarity, merocyanine dyes usually align in antiparallel dimers in an ordered fashion. The examination of twenty different molecules with ground state dipole moments up to 15.0 D shows that by a high dipolarity and well-defined sterics, the molecules pack in a highly regular two-dimensional brickwork-type structure, which is beneficial for hole transport. Utilization of these molecules for organic thin-film transistors (OTFTs) leads to hole mobility values up to 0.21 cm²/Vs. By fabrication of single crystal field-effect transistors (SCFETs) for the derivative showing the highest mobility values in OTFTs, even hole mobilities up to 2.34 cm²/Vs are achieved. Hence, merocyanine based transistors show hole mobility values comparable to those of conventional p-type organic semiconductors and therefore high ground state dipole moments are not necessarily disadvantageous regarding high mobility applications. By examination of a different series of ten merocyanine dyes with the same chromophore backbone but different donor substituents, it is demonstrated that the size of the donor has a significant influence on the optical properties of thin films. For small and rigid donor substituents, a hypsochromic shift of the absorption compared to the monomer absorption in solution is observed due to the card stack like packing of the molecules in the solid state. By utilization of sterical demanding or flexible donor substituents, a zig-zag type packing is observed, leading to a bathochromical shift of the absorption. These packing motifs and spectral shifts with an offset of 0.93 eV of the H- and J-bands comply with the archetype examples of H- and J-aggregates from Kasha's exciton theory.}, subject = {Exziton}, language = {en} } @phdthesis{LiebschergebBloehbaum2020, author = {Liebscher [geb. Bl{\"o}hbaum], Julia}, title = {Side chain functional poly(2-oxazoline)s for biomedical applications}, doi = {10.25972/OPUS-20396}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203960}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2020}, abstract = {The aim of the thesis was to develop water soluble poly(2-oxazoline) (POx) copolymers with new side group functionalities, which can be used for the formation of hydrogels in biomedical applications and for the development of peptide-polymer conjugates. First, random copolymers of the monomer MeOx or EtOx with ButEnOx and EtOx with DecEnOx were synthesized and characterized. The vinyl functionality brought into the copolymer by the monomers ButEnOx and DecEnOx would later serve for post-polymerization functionalization. The synthesized copolymers were further functionalized with thiols via post-polymerization functionalization using a newly developed synthesis protocol or with a protected catechol molecule for hydrogel formation. For the formation of peptide-polymer conjugates, a cyclic thioester, namely thiolactone acrylamide and an azlactone precursor, whose synthesis was newly developed, were attached to the side chain of P(EtOx-co-ButEnOx) copolymers. The application of the functionalized thiol copolymers as hydrogels using thiol-ene chemistry for cross-linking was demonstrated. The swelling behavior and mechanical properties were characterized. The hydrophilicity of the network as well as the cross-linking density strongly influenced the swelling behavior and the mechanical strength of the hydrogels. All hydrogels showed good cell viability results. The hydrogel networks based on MeOx and EtOx were loaded with two dyes, fluorescein and methylene blue. It was observed that the uptake of the more hydrophilic dye fluorescein depended more on the ability of the hydrogel to swell. In contrast, the uptake of the more hydrophobic dye methylene blue was less dependent on the swelling degree, but much more on the hydrophilicity of the network. For the potential application as cartilage glue, (biohybrid) hydrogels were synthesized based on the catechol-functionalized copolymers, with and without additional fibrinogen, using sodium periodate as the oxidizing agent. The system allowed for degradation due to the incorporated ester linkages at the cross-linking points. The swelling behavior as well as the mechanical properties were characterized. As expected, hydrogels with higher degrees of cross-linking showed less swelling and higher elastic modulus. The addition of fibrinogen however increased the elasticity of the network, which can be favorable for the intended application as a cartilage glue. Biological evaluation clearly demonstrated the advantage of degradable ester links in the hydrogel network, where chondrocytes were able to bridge the artificial gap in contrast to hydrogels without any ester motifs. Lastly, different ways to form peptide-polymer conjugates were presented. Peptides were attached with the thiol of the terminal cysteine group to the vinyl side chain of P(EtOx-co-ButEnOx) copolymers by radical thiol-ene chemistry. Another approach was to use a cyclic thioester, thiolactone, or an azlactone functionality to bind a model peptide via native chemical ligation. The two latter named strategies to bind peptides to POx side chains are especially interesting as one and in the case of thiolactone two free thiols are still present at the binding site after the reaction, which can, for example, be used for further thiol-ene cross-linking to form POx hydrogels. In summary, side functional poly(oxazoline) copolymers show great potential for numerous biomedical applications. The various side chain functionalities can be introduced by an appropriate monomer or by post-polymerization functionalization, as demonstrated. By their multi-functionality, hydrogel characteristics, such as cross-linking degree and mechanical strength, can be fine-tuned and adjusted depending on the application in the human body. In addition, the presented chemoselective and orthogonal reaction strategies can be used in the future to synthesize polymer conjugates, which can, for example, be used in drug delivery or in tissue regeneration.}, subject = {Polymere}, language = {en} }