@article{MufusamaFeineisMudogoetal.2019, author = {Mufusama, Jean-Pierre and Feineis, Doris and Mudogo, Virima and Kaiser, Marcel and Brun, Reto and Bringmann, Gerhard}, title = {Antiprotozoal dimeric naphthylisoquinolines, mbandakamines B\(_3\) and B\(_4\), and related 5,8′-coupled monomeric alkaloids, ikelacongolines A-D, from a Congolese Ancistrocladus liana}, series = {RSC Advances}, volume = {9}, journal = {RSC Advances}, number = {21}, doi = {10.1039/C9RA01784D}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201141}, pages = {12034-12046}, year = {2019}, abstract = {From the leaves of a botanically and phytochemically as yet unexplored Ancistrocladus liana discovered in the rainforests of the Central region of the Democratic Republic of the Congo in the vicinity of the town of Ikela, six new naphthylisoquinoline alkaloids were isolated, viz., two constitutionally unsymmetric dimers, the mbandakamines B\(_3\) (3) and B\(_4\) (4), and four related 5,8′-linked monomeric alkaloids, named ikelacongolines A-D (5a, 5b, 6, and 7). The dimers 3 and 4 are structurally unusual quateraryls comprising two 5,8′-coupled monomers linked via a sterically strongly constrained 6′,1′′-connection between their naphthalene units. These compounds contain seven elements of chirality, four stereogenic centers and three consecutive chiral axes. They were identified along with two known related compounds, the mbandakamines A (1) and B\(_2\) (2), which had so far only been detected in two Ancistrocladus species indigenous to the Northwestern Congo Basin. In addition, five known monomeric alkaloids, previously found in related Central African Ancistrocladus species, were isolated from the here investigated Congolese liana, three of them belonging to the subclass of 5,8′-coupled naphthylisoquinoline alkaloids, whereas two compounds exhibited a less frequently occurring 7,8′-biaryl linkage. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR), chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. The mbandakamines B\(_3\) (3) and B\(_4\) (4) displayed pronounced activities in vitro against the malaria parasite Plasmodium falciparum and the pathogen of African sleeping sickness, Trypanosoma brucei rhodesiense.}, language = {en} } @article{MuellerLuettigMalyetal.2019, author = {Mueller, Stefan and L{\"u}ttig, Julian and Mal{\´y}, Pavel and Ji, Lei and Han, Jie and Moos, Michael and Marder, Todd B. and Bunz, Uwe H. F. and Dreuw, Andreas and Lambert, Christoph and Brixner, Tobias}, title = {Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways}, series = {Nature Communications}, volume = {10}, journal = {Nature Communications}, doi = {10.1038/s41467-019-12602-x}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202529}, pages = {4735}, year = {2019}, abstract = {Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions.}, language = {en} } @phdthesis{Mladenovic2008, author = {Mladenovic, Milena}, title = {Theoretical Investigation into the Inhibition of Cystein Proteases}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-25763}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {Although known about and investigated since the late 1970's, the picture of the basic principles governing inhibitor strengths and the structure-activity relationships of the cysteine protease inhibition mechanism is still very incomplete. Computational approaches can be a very useful tool for investigating such questions, as they allow the inspection of single, specific effects in isolation from all others, in a manner very difficult to achieve experimentally. The ab initio treatments of such large systems like proteins are still not feasible. However, there is a vast number of computational approaches capable of dealing with protein structures with reasonable accuracy. This work presents a summary of theoretical investigations into cysteine protease cathepsin B using a range of methods. We have concentrated on the investigation of cysteine protease inhibition by epoxide- and aziridine-based inhibitors in order to obtain better insight into these important topics. Various model systems are simulated by means of pure quantum mechanical methods and by hybrid (QM/MM) methods. Both approaches provide a static picture. Dynamical effects are then accounted for by additional molecular dynamics (MD) simulations, using both classical and QM/MM MD approaches. The quantum mechanical approach was used to study very small model systems consisting only of the electrophilic warhead of the inhibitor (both substitituted and not) and molecular moieties simulating a very simplified protein active site (methylthiolate instead of Cys29 and methylimidazolium instead of His199 residue) and solvent surroundings (two waters or two ammonium ions, in combination with a continuum solvent model). Although simple, such a system provides a good description of the most important interactions involved in the inhibition reaction. It also allows investigation of the influence of the properties of the electrophilic warhead on the reaction rate. Beside the properties of the electrophilic warhead, the protein and solvent environment is also an important factor in the irreversible deactivation of the enzyme active site by the inhibitor. The non-covalent interactions of the inhibitor with the oxyanion hole and other subsites of the enzyme, as well as its interaction with the solvent molecules, need to be explicitly taken into account in the calculations, because of their possible impact on the reaction profile. As molecular modeling methods allow the treatment of such large systems, but lack the possibility of describing covalent interactions, our method of choice was the combined quantum mechanics/molecular modeling approach. By splitting the system into a smaller part that undergoes the bond cleavage/formation process and must be treated quantum mechanically, and a larger part, comprised of the rest of the protein, which could be treated using force fields, we managed to simulate the system at the desired precision. Our investigations concentrated on the role of His199 in the inhibition mechanism as well as on the structure-reactivity relationships between cysteine protease and various inhibitors, yielding new insight into the kinetics, regio- and stereospecificity of the inhibition. In particular, our calculations provide the following insights: i.) an explanation for the regioselectivity of the reaction, and original insight into which interactions affect the stereoselectivity; ii.) a clear model which explains the known structure-activity relationships and connects these effects with the pH-dependency of the inhibition; iii.) our computations question the generally accepted two-step model by showing that substituent effects accelerate the irreversible step to such an extent that the achievement of an equilibrium in the first step is doubtful; iv.) by way of theoretical characterizations of aziridine models, the reasons for similarities and differences in the mode of action of epoxide- and aziridine-based inhibitors are elucidated; and finally, v.) combining our results with experimental knowledge will allow rational design of new inhibitors. To account for dynamical effects as well, molecular dynamics (MD) computations were also performed. In these calculations the potential energy was computed at the force field level. The results not only supported and clarified the QM/MM results, but comparison with previous X-ray structures helped correct existing errors in the available geometrical models and resolved inconsistencies in the weighting of various factors governing the inhibition. In the work the first QM/MM MD calculations on the active site of the cysteine proteases are presented. In contrast to the MD simulations, these calculations used potential energies computed at the QM/MM-level. With the help of these computations we sought to address strongly disputed questions about the reasons for the existence of the active site ion pair and its role in the high activity of the enzyme.}, subject = {Quantenchemie}, language = {en} } @article{MieczkowskiSteinmetzgerBessietal.2021, author = {Mieczkowski, Mateusz and Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Pena, Vladimir and H{\"o}bartner, Claudia}, title = {Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine}, series = {Nature Communications}, volume = {12}, journal = {Nature Communications}, doi = {10.1038/s41467-021-23932-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-270274}, year = {2021}, abstract = {Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.}, language = {en} } @article{MieczkowskiSteinmetzgerBessietal.2021, author = {Mieczkowski, Mateusz and Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Pena, Vladimir and H{\"o}bartner, Claudia}, title = {Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine}, series = {Nature Communications}, volume = {12}, journal = {Nature Communications}, doi = {10.1038/s41467-021-23932-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254527}, pages = {3549}, year = {2021}, abstract = {Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.}, language = {en} } @phdthesis{Michail2021, author = {Michail, Evripidis}, title = {Design and Development of a Two-Photon Absorption Induced Fluorescence Spectrometer and the Investigation of Nonlinear Optical Properties of Organic Chromophores}, doi = {10.25972/OPUS-24218}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242185}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Main objectives of the present dissertation can be divided in two parts. The first part deals with setting up a spectroscopic technique for reliable and accurate measurements of the two-photon absorption (2PA) cross section spectra. In the second part, this firmly established experimental technique together with conventional spectroscopic characterization, quantum-chemical computations and theoretical modelling calculations was combined and therefore used as a tool to gain information for the so-called structure-property relationship through several molecular compounds.}, subject = {Nonlinear Optical Properties of Organic Materials}, language = {en} } @article{MezaChinchaLindnerSchindleretal.2020, author = {Meza-Chincha, Ana-Lucia and Lindner, Joachim O. and Schindler, Dorothee and Schmidt, David and Krause, Ana-Maria and R{\"o}hr, Merle I. S. and Mitrić, Roland and W{\"u}rthner, Frank}, title = {Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation}, issn = {2041-6539}, doi = {10.1039/d0sc01097a}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204653}, year = {2020}, abstract = {Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites.}, language = {en} } @phdthesis{MezaChincha2021, author = {Meza Chincha, Ana Lucia}, title = {Catalytic Water Oxidation with Functionalized Ruthenium Macrocycles}, doi = {10.25972/OPUS-20962}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-209620}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {In light of the rapidly increasing global demand of energy and the negative effects of climate change, innovative solutions that allow an efficient transition to a carbon-neutral economy are urgently needed. In this context, artificial photosynthesis is emerging as a promising technology to enable the storage of the fluctuating energy of sunlight in chemical bonds of transportable "solar fuels". Thus, in recent years much efforts have been devoted to the development of robust water oxidation catalysts (WOCs) leading to the discovery of the highly reactive Ru(bda) (bda: 2,2'-bipyridine-6,6'-dicarboxylic acid) catalyst family. The aim of this thesis was the study of chemical and photocatalytic water oxidation with functionalized Ruthenium macrocycles to explore the impact of substituents on molecular properties and catalytic activities of trinuclear macrocyclic Ru(bda) catalysts. A further objective of this thesis comprises the elucidation of factors that influence the light-driven water oxidation process with this novel class of supramolecular WOCs.}, subject = {Rutheniumkomplexe}, language = {en} } @article{MetropoulosEngelsPeyerimhoff1993, author = {Metropoulos, B. and Engels, Bernd and Peyerimhoff, S.D.}, title = {On the chemi-ionization reaction O + CH ----> HCO\(^+\)+ e\(^-\). Coollinear O-CH Approach}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58963}, year = {1993}, abstract = {We have investigated theoretically the importance of the O(\(^3\)P)+CH(a\(^4\sum^-\)) and the O(\(^3\)P)+CH(X\(^2\Pi\)) channels in the collinear chemi-ionization reaction O+CH->HCO\(^+\) +e\(^-\). We have found that both channels may lead to chemi-ionization via favorable Franck-Condon overlaps with the states ofthe ionic species.}, subject = {Organische Chemie}, language = {en} } @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} } @article{LiaqatStillerMicheletal.2020, author = {Liaqat, Anam and Stiller, Carina and Michel, Manuela and Sednev, Maksim V. and H{\"o}bartner, Claudia}, title = {N\(^6\)-Isopentenyladenosine in RNA Determines the Cleavage Site of Endonuclease Deoxyribozymes}, series = {Angewandte Chemie International Edition}, journal = {Angewandte Chemie International Edition}, edition = {Early View}, doi = {10.1002/ange.202006218}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212121}, year = {2020}, abstract = {RNA-cleaving deoxyribozymes can serve as selective sensors and catalysts to examine the modification state of RNA. However, site-specific endonuclease deoxyribozymes that selectively cleave posttranscriptionally modified RNA are extremely rare and their specificity over unmodified RNA is low. In this study, we report that the native tRNA modification N\(^6\)-isopentenyladenosine (i\(^6\)A) strongly enhances the specificity and has the power to reconfigure the active site of an RNA-cleaving deoxyribozyme. Using in vitro selection, we identified a DNA enzyme that cleaves i\(^6\)A-modified RNA at least 2500-fold faster than unmodified RNA. Another deoxyribozyme shows unique and unprecedented behaviour by shifting its cleavage site in the presence of the i\(^6\)A RNA modification. Together with deoxyribozymes that are strongly inhibited by i\(^6\)A, these results highlight intricate ways of modulating the catalytic activity of DNA by posttranscriptional RNA modifications.}, language = {en} } @article{LiaqatSednevStilleretal.2021, author = {Liaqat, Anam and Sednev, Maksim V. and Stiller, Carina and H{\"o}bartner, Claudia}, title = {RNA-cleaving deoxyribozymes differentiate methylated cytidine isomers in RNA}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, doi = {10.1002/anie.202106517}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256519}, pages = {19058-19062}, year = {2021}, abstract = {Deoxyribozymes are emerging as modification-specific endonucleases for the analysis of epigenetic RNA modifications. Here, we report RNA-cleaving deoxyribozymes that differentially respond to the presence of natural methylated cytidines, 3-methylcytidine (m\(^3\)C), N\(^4\)-methylcytidine (m\(^4\)C), and 5-methylcytidine (m\(^5\)C), respectively. Using in vitro selection, we found several DNA catalysts, which are selectively activated by only one of the three cytidine isomers, and display 10- to 30-fold accelerated cleavage of their target m\(^3\)C-, m\(^4\)C- or m\(^5\)C-modified RNA. An additional deoxyribozyme is strongly inhibited by any of the three methylcytidines, but effectively cleaves unmodified RNA. The mXC-detecting deoxyribozymes are programmable for the interrogation of natural RNAs of interest, as demonstrated for human mitochondrial tRNAs containing known m\(^3\)C and m\(^5\)C sites. The results underline the potential of synthetic functional DNA to shape highly selective active sites.}, language = {en} } @article{LiaqatSednevStilleretal.2021, author = {Liaqat, Anam and Sednev, Maksim V. and Stiller, Carina and H{\"o}bartner, Claudia}, title = {RNA-Cleaving Deoxyribozymes Differentiate Methylated Cytidine Isomers in RNA}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {35}, doi = {10.1002/anie.202106517}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254544}, pages = {19058-19062}, year = {2021}, abstract = {Deoxyribozymes are emerging as modification-specific endonucleases for the analysis of epigenetic RNA modifications. Here, we report RNA-cleaving deoxyribozymes that differentially respond to the presence of natural methylated cytidines, 3-methylcytidine (m\(^3\)C), N\(^4\)-methylcytidine (m\(^4\)C), and 5-methylcytidine (m\(^5\)C), respectively. Using in vitro selection, we found several DNA catalysts, which are selectively activated by only one of the three cytidine isomers, and display 10- to 30-fold accelerated cleavage of their target m\(^3\)C-, m\(^4\)C- or m\(^5\)C-modified RNA. An additional deoxyribozyme is strongly inhibited by any of the three methylcytidines, but effectively cleaves unmodified RNA. The m\(^X\)C-detecting deoxyribozymes are programmable for the interrogation of natural RNAs of interest, as demonstrated for human mitochondrial tRNAs containing known m\(^3\)C and m\(^5\)C sites. The results underline the potential of synthetic functional DNA to shape highly selective active sites.}, language = {en} } @incollection{LiaqatSednevHoebartner2022, author = {Liaqat, Anam and Sednev, Maksim V. and H{\"o}bartner, Claudia}, title = {In Vitro Selection of Deoxyribozymes for the Detection of RNA Modifications}, series = {Ribosome Biogenesis: Methods and Protocols}, booktitle = {Ribosome Biogenesis: Methods and Protocols}, publisher = {Humana Press}, isbn = {978-1-0716-2501-9}, doi = {10.1007/978-1-0716-2501-9_10}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-279208}, publisher = {Universit{\"a}t W{\"u}rzburg}, pages = {167-179}, year = {2022}, abstract = {Deoxyribozymes are artificially evolved DNA molecules with catalytic abilities. RNA-cleaving deoxyribozymes have been recognized as an efficient tool for detection of modifications in target RNAs and provide an alternative to traditional and modern methods for detection of ribose or nucleobase methylation. However, there are only few examples of DNA enzymes that specifically reveal the presence of a certain type of modification, including N6-methyladenosine, and the knowledge about how DNA enzymes recognize modified RNAs is still extremely limited. Therefore, DNA enzymes cannot be easily engineered for the analysis of desired RNA modifications, but are instead identified by in vitro selection from random DNA libraries using synthetic modified RNA substrates. This protocol describes a general in vitro selection stagtegy to evolve new RNA-cleaving DNA enzymes that can efficiently differentiate modified RNA substrates from their unmodified counterpart.}, language = {en} } @phdthesis{Liaqat2022, author = {Liaqat, Anam}, title = {Artificial Evolution of Nucleic Acid Catalysts and their Use for Studying RNA}, doi = {10.25972/OPUS-28311}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-283111}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {RNA molecules play diverse roles in biological systems. Post-transcriptional RNA modifications and dynamic structures enhance the functional diversity of RNA. A prerequisite for studying their biological significance is the availability of reliable methods for the detection of RNA modifications and structures. Several promising approaches have been developed in the last few decades; however, efficient, and versatile tools are still required to study the dynamic features of RNA. This thesis focuses on the development of nucleic acid catalysts as a tool to address the current needs in studying RNA. The major part of this thesis aimed at the development of deoxyribozymes as a tool for the detection of RNA modifications. Using in vitro selection from a random DNA library, we found deoxyribozymes that are sensitive to N 6 -isopentenyladenosine (i6A), a native tRNA modification and structural analogue of m6A. The in vitro evolution identified three classes of DNA enzymes: AA, AB08, and AC17 DNAzymes that showed distinct response to i6A modification and showed strong discrimination between structural analogues, i.e., m6A and i6A. In the continuation of the project, we attempted to develop RNA-cleaving deoxyribozymes that differentially respond to monomethylated cytidine isomers, 3-methylcytidine (m3C), N4 - methylcytidine (m4C), and 5-methylcytidine (m5C). Several deoxyribozymes were identified from in vitro selection, which are selective for a specific methylated cytidine isomer. The characterization of AL112, AM101, AN05, and AK104 catalysts confirmed the successful evolution of modification-specific and general deoxyribozymes that showed a broad substrate scope. In order to accelerate the DNAzymes discovery, a high throughput sequencing method (DZ-seq) was established that directly quantifies the RNA cleavage activity and cleavage site from deep sequencing data. The libraries contained information about cleavage status, cleavage site and sequence of deoxyribozymes and RNA substrate. The fraction cleaved (FC) data obtained from Dz-seq was validated for a subset of deoxyribozmes using conventional gel based kinetic assay and showed a good linear correlation (R2 = 0.91). Dz-seq possesses a great potential for the discovery of novel deoxyribozymes for the analysis of various RNA modifications in the future. The second objective of the current study was the development of structure-specific RNA labeling ribozymes. Here, we attempted to develop ribozymes that targets RNA of interest by structure-specific interaction rather than base-pairing and focused on a specific RNA G-quadruplex as the target. Two subsequent selection experiments led to the identification of the adenylyltransferase ribozymes AO10.2 and AR9. The partial characterization of these catalysts showed that A010.2 was unable to recognize intact BCL2 structure, but it turned out as the first reported trans-active ribozyme that efficiently labeled uridine in a defined substrate RNA hybridized to the ribozyme. The other ribozyme AR9 was shown to serve as a trans-active, self-labeling ribozyme that catalyzed adenylyl transferase reaction in the presence of the intact BCL2 sequence. Based on these preliminary findings, we envision that AR9 could potentially serve as a reporter RNA by self-labeling in the presence of an RNA G-quadruplex. However, both AO10.2 and AR9 still require more detailed characterization for their potential applications.}, language = {en} } @phdthesis{Li2009, author = {Li, Xueqing}, title = {Hydrogen Bond-directed Self-assembly of Perylene Bisimide Organogelators}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-43727}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2009}, abstract = {Perylene bisimide (PBI) dyes are a widely used class of industrial pigments, and currently have gained significant importance for organic-based electronic and optical devices. Structural modification at the PBI core results in changes of the optical and electronic properties, which enable tailored functions. Moreover, the aggregation behavior of PBIs is alterable and controllable to achieve new materials, among which organogels are of particular interest because of their potential for applications as supramolecular soft materials. In this work, new PBI-based organic gelators were designed, synthesized, and characterized, and the aggregation behaviors under different conditions were intensively studied by various spectroscopic and microscopic methods. In chapter 2, a brief overview is given on the structural and functional features of organogel systems. The definition, formation and reversibility of organogels are introduced. Some examples on dye based organogel are selected, among which PBI-based organogelators reported so far are especially emphasized. Some basic knowledges of supramolecular chirality are also overviewed such as characterization, amplification, and symmetry breaking of the chiral aggregates. According to our former experiences, PBIs tend to form aggregates because the planer aromatic cores interact with one another by pi-pi interaction. In chapter 3, a new PBI molecule is introduced which possesses amide groups between the conjugated core and periphery alkyl chains. It is found that well oriented aggregates are formed by hydrogen bonding and the pi-pi interaction of the cores. These interactions enable the aggregates to grow in one-dimension forming very long fibers, and these fibers further intercross to 3D network structures, e.g., organogels. In comparison to the very few PBI-based gelators reported before, one advantage of this gelator is that, it is more versatile and can gelate a wide range of organic solvents. Moreover, the well-organized fibers that are composed of extended \&\#960;-stacks provide efficient pathways for n-type charge carriers. Interestingly, AFM studies reveal that the PBI molecules form well-defined helical fibers in toluene. Both left-handed (M) and right-handed (P) helicities can be observed without any preference for one handedness because the building block is intrinsically achiral. In chapter 4, we tried to influence the M/P enantiomeric ratio by applying external forces. For example, we utilized chiral solvents to generate chiral aggregates with a preferential handedness. AFM analysis of the helices showed that a enantiomeric ratio of about 60: 40 can be achieved by aggregation in chiral solvents R- or S-limonene. Moreover, the long aggregated fibres can align at macroscopic level in vortex flows upon rotary stirring In chapter 5, bulky tetra-phenoxy groups are introduced in the bay area of the PBI gelator. The conjugated core of the new molecule is now distorted because of the steric hindrance. UV/Vis studies reveal a J-type aggregation in apolar solvents like MCH due to intermolecular pi-pi-stacking and hydrogen-bonding interactions. Microscopic studies reveal formation of columnar aggregates in apolar solvent MCH, thus this molecule lacks the ability to form gels in this solvent, but form highly fluorescent lyotropic mesophases at higher concentration. On the other hand, in polar solvents like acetone and dioxane, participation of the solvent molecules in hydrogen bonding significantly reduced the aggregation propensity but enforced the gel formation. The outstanding fluorescence properties of the dye in both J-aggregated viscous lyotropic mesophases and bulk gel phases suggest very promising applications in photonics, photovoltaics, security printing, or as fluorescent sensors. In chapter 6, we did some studies on combining PBI molecules with inorganic gold nanorods. Gold nanorods were synthesized photochemically. By virtue of the thioacetate functionalized PBIs, the rods were connected end to end to form gold nanochains, which were characterized by absorption spectra and TEM measurement. Such chromophore-nanorod hybrids might be applied to guide electromagnetic radiation based on optical antenna technology.}, subject = {Perylenderivate}, language = {en} } @article{LeiningerLanzendoerferChristl1983, author = {Leininger, H. and Lanzend{\"o}rfer, F. and Christl, Manfred}, title = {{\"U}ber die Reduktion des Benzvalenozonids zum cis-1,3-Cyclobutandimethanol mit LiAlH\(_4\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58130}, year = {1983}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} } @article{LehmannDechantWehetal.2020, author = {Lehmann, Matthias and Dechant, Moritz and Weh, Dominik and Freytag, Emely}, title = {Metal Phthalocyanine-Fullerene Dyads: Promising Lamellar Columnar Donor-Acceptor Liquid Crystal Phases}, series = {ChemPlusChem}, volume = {85}, journal = {ChemPlusChem}, number = {8}, doi = {10.1002/cplu.202000540}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218531}, pages = {1934 -- 1938}, year = {2020}, abstract = {Liquid crystal (LC) shape-amphiphiles with a disc tethered to a fullerene have been intensely studied for the application in photovoltaics, and helical nanosegregation of C\(_{60}\) has been claimed around the π-stacking disks based on X-ray results. The most promising materials reported to date have been resynthesized and studied comprehensively by XRS, density measurements, modelling, and electron density reconstruction. In contrast to previous reports, the results indicate that metal phthalocyanine-fullerene mesogens pack in lamellar columnar phases with p2gm symmetry. Fullerenes assemble in layers and are flanked by phthalocyanine columns, thus explaining the balanced charge carrier mobility of electrons and holes. Such variable donor-acceptor structures are promising for organic electronic applications.}, language = {en} } @article{LehmannBaumannLambovetal.2021, author = {Lehmann, Matthias and Baumann, Maximilian and Lambov, Martin and Eremin, Alexey}, title = {Parallel polar dimers in the columnar self-assembly of umbrella-shaped subphthalocyanine mesogens}, series = {Advanced Functional Materials}, volume = {31}, journal = {Advanced Functional Materials}, number = {38}, doi = {10.1002/adfm.202104217}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256343}, year = {2021}, abstract = {The self-assembly of umbrella-shaped mesogens is explored with subphthalocyanine cores and oligo(thienyl) arms with different lengths in the light of their application as light-harvesting and photoconducting materials. While the shortest arm derivatives self-assemble in a conventional columnar phase with a single mesogen as a repeating unit, the more extended derivatives generate dimers that pile up into liquid crystalline columns. In contrast to the antiparallel arrangement known from single crystals, the present mesogens align as parallel dimers in polar columnar phases as confirmed by X-ray scattering, experimental densities, dielectric spectroscopy, second harmonic generation, alignment, and conductivity studies. UV-vis and fluorescence spectroscopies reveal a broad absorption in the visible range and only weak emission of the Q-band. Thus, these light-collecting molecules forming strongly polar columnar mesophases are attractive for application in the area of photoconductive materials.}, language = {en} } @article{LanzendoerferChristl1983, author = {Lanzend{\"o}rfer, Franz and Christl, Manfred}, title = {3,4-Bismethylentricyclo[3.1.0.02,6]hexan - Synthese und Diels-Alder-Addition an Tetracyanethylen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30263}, year = {1983}, abstract = {No abstract available}, language = {en} } @article{LambovHensiekPoeppleretal.2020, author = {Lambov, Martin and Hensiek, Nicola and P{\"o}ppler, Ann-Christin and Lehmann, Matthias}, title = {Columnar Liquid Crystals from Star-Shaped Conjugated Mesogens as Nano-Reservoirs for Small Acceptors}, series = {ChemPlusChem}, volume = {85}, journal = {ChemPlusChem}, number = {10}, doi = {10.1002/cplu.202000341}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218014}, pages = {2219 -- 2229}, year = {2020}, abstract = {Shape-persistent conjugated mesogens with oligothiophene arms of different lengths have been synthesized. Such mesogens possess free intrinsic space between their conjugated arms. They form columnar liquid-crystalline phases, in which the void is filled by dense helical packing in the neat phase similar to an oligo(phenylene vinylene) derivative of equal size. The void can also be compensated by the inclusion of the small acceptor molecule 2,4,7-trinitrofluorenone. In solution, the acceptor interacts with the core as the largest π-surface, while in the solid material, it is incorporated between the arms and sandwiched by the star-shaped neighbours along the columnar assemblies. The TNF acceptors are not nanosegregated from the star-shaped donors, thus the liquid crystal structure converts to a nano-reservoir for TNF (endo-receptor). These host-guest arrangements are confirmed by comprehensive X-ray scattering experiments and solid-state NMR spectroscopy. This results in ordered columnar hexagonal phases at high temperatures, which change to helical columnar mesophases or to columnar soft crystals at room temperature.}, language = {en} } @unpublished{LambertVoelkerKochetal.2015, author = {Lambert, Christoph and V{\"o}lker, Sebastian F. and Koch, Federico and Schmiedel, Alexander and Holzapfel, Marco and Humeniuk, Alexander and R{\"o}hr, Merle I. S. and Mitric, Roland and Brixner, Tobias}, title = {Energy Transfer Between Squaraine Polymer Sections: From helix to zig-zag and All the Way Back}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.5b03644}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159607}, year = {2015}, abstract = {Joint experimental and theoretical study of the absorption spectra of squaraine polymers in solution provide evidence that two different conformations are present in solution: a helix and a zig-zag structure. This unique situation allows investigating ultrafast energy transfer processes between different structural segments within a single polymer chain in solution. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. We combine here femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy showing that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zig-zag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the density of states between donor and acceptor polymer segments because of very small reorganization energy in these cyanine-like chromophores.}, language = {en} } @phdthesis{Kunz2018, author = {Kunz, Valentin}, title = {Supramolecular Approaches for Water Oxidation Catalysis with Ruthenium Complexes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-154820}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2018}, abstract = {The catalytic splitting of water into its elements is an important reaction to establish hydrogen as a solar fuel. The bottle-neck of this process is considered to be the oxidative half reaction generating oxygen, and good catalysts are required to handle the complicated redox chemistry involved. As can be learned from nature, the incorporation of the catalytically active species into an appropriate matrix can help to improve the overall performance. Thus, the aim of the present thesis was to establish novel supramolecular approaches to improve water oxidation catalysis using the catalytically active {Ru(bda)} fragment as key motive (bda = 2,2'-bipyridine-6,6'-dicarboxylate). First, the synthesis of ruthenium catalysts gathering three {Ru(bda)} water oxidation subunits in a macrocyclic fashion is described. By using bridging bipyridine ligands of different lengths, metallosupramolecular macrocycles with distinct sizes have been obtained. Interestingly, an intermediate ring size has been proven to be optimal for the catalytic water oxidation. Detailed kinetic, spectroscopic, and theoretical studies helped to identify the reaction mechanism and to rationalize the different catalytic activities. Furthermore, solubilizing side chains have been introduced for the most active derivative to achieve full water solubility. Secondly, the {Ru(bda)} fragment was embedded into supramolecular aggregates to generate more stable catalytic systems compared to a homogeneous reference complex. Therefore, the catalyst fragment was equipped with axial perylene bisimide (PBI) ligands, which facilitate self-assembly. Moreover, the influence of the different accessible aggregate morphologies on the catalytic performance has been investigated.}, subject = {Ruthenium Komplexe}, language = {en} } @article{KunzLabesWieseetal.2014, author = {Kunz, Anna Lena and Labes, Antje and Wiese, Jutta and Bruhn, Torsten and Bringmann, Gerhard and Imhoff, Johannes F.}, title = {Nature's Lab for Derivatization: New and Revised Structures of a Variety of Streptophenazines Produced by a Sponge-Derived Streptomyces Strain}, series = {Marine Drugs}, volume = {12}, journal = {Marine Drugs}, number = {4}, issn = {1660-3397}, doi = {10.3390/md12041699}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-116816}, pages = {1699-1714}, year = {2014}, abstract = {Eight streptophenazines (A-H) have been identified so far as products of Streptomyces strain HB202, which was isolated from the sponge Halichondria panicea from the Baltic Sea. The variation of bioactivities based on small structural changes initiated further studies on new derivatives. Three new streptophenazines (I-K) were identified after fermentation in the present study. In addition, revised molecular structures of streptophenazines C, D, F and H are proposed. Streptophenazines G and K exhibited moderate antibacterial activity against the facultative pathogenic bacterium Staphylococcus epidermidis and against Bacillus subtilis. All tested compounds (streptophenazines G, I-K) also showed moderate activities against PDE 4B.}, language = {en} } @phdthesis{Kriegisch2005, author = {Kriegisch, Volker}, title = {Electron transfer processes between organic redox centres and electrodes via active bridges in self-assembled monolayers}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-15892}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2005}, abstract = {Cyclovoltammetrische Messungen der Ferrocenalkylthiole 1 - 3 belegen, dass homogene, gemischte Monolagen aus redoxaktiven Verbindungen und redoxinaktiven Alkylthiolen gebildet werden. Die von Creager et al. bestimmten ET Raten der Ferrocenalkylthiole 1 - 3 konnten hierbei verifiziert werden. Wie erwartet erfolgt eine Abnahme der ET Geschwindigkeit bei einer Kettenverl{\"a}ngerung des Alkylspacers von 2 nach 3. Eine unterschiedliche Konnektivit{\"a}t zwischen Redoxzentrum und Alkylspacer, z. B. die Einf{\"u}hrung einer Carbonyl-Funktion im Falle von 1, unter Beibehaltung der Kettenl{\"a}nge zeigt keinen bemerkbaren Einfluß auf den ET. Trotzt vergleichbaren Abstands der aromatischen Ferrocenthiole 4 und 5 zu der C8-Alkyl-Verbindung 2 zwischen Redoxzentrum und Elektrode, weisen diese aufgrund ihrer starken Konjugation sehr hohe ET Geschwindigkeiten auf. Die elektronischen Kopplungsfaktoren selbst deuten auf einen nichtadiabtischen ET zwischen Redoxzentrum und Elektrode hin. Wie erwartet kommt es zu einem Anwachsen der Kopplungsfaktoren bei sich verk{\"u}rzender Kettenl{\"a}nge oder bei Einf{\"u}hrung konjugierter Spacersysteme. Zusammenfassend kann gesagt werden, dass Erfahrungen hinsichtlich der Pr{\"a}paration der Monolagen gesammelt, die gemessenen ET Raten f{\"u}r der literaturbekannten Verbindungen 1 - 3 best{\"a}tigt und diese Informationen auf die konjugierten Verbindungen 4 und 5 angewandt werden konnten. Im zweiten Teil wurden die Triarylamin- (29, 32) und Phenothiazinalkylthiole (35) bez{\"u}glich ihres ET Verhaltens in gemischten Monolagen untersucht. Mittels Cyclovoltammetrie konnte gezeigt werden, daß einheitlich geformte, verd{\"u}nnte Monolagen vorliegen. Die ET Raten der Triarylamin- (29, 32) und Phenithiazinalkylthiole (35) sind jedoch um den Faktor 10 bis 100 h{\"o}her als vergleichbare Ferrocenalkylthiole gleicher Kettenl{\"a}nge [1, 2], wohingegen f{\"u}r Monolagen, welche [Ru(bpy)2(pp)]+-Alkythiole enthalten, {\"a}quivalente Werte gefunden wurden [3]. Die ET Geschwindigkeit wird von zwei Parametern beeinflusst: dem elektronischen Kopplungsmatrixelement und der Regorganisationsenergie \&\#61548;\&\#61472; [4]. Die ET Geschwindigkeit in Donor-substituierten Alkylthiolen wird haupts{\"a}chlich durch \&\#61548; beeinflusst und sogar kleine {\"A}nderungen dieser zeigen eine große Auswirkung auf die zu untersuchenden Prozesse. Aus diesem Grund wird eine Zunahme der ET Geschwindigkeit von Ferrocen (hohe Reorganisationsenergie) {\"u}ber die Phenothiazinverbindung 35 und [Ru(bpy)2(pp)]+ zu den Triarylaminchromophoren 29 und 32 (niedrige Reorganisationsenergie) beobachtet. Weiterhin spielt, im Gegensatz zu Beobachtung von Creager et al. an {\"a}quivalenten Ferrocenverbingungen, die Anbindung des Redoxzentrums an den Alkylspacer eine bedeutende Rolle. Im Falle der elektronenreichen Ether-verbr{\"u}ckten Verbindung 29 wird der ET nicht alleine durch \&\#61548;, sondern ebenso durch mesomere Effekte bestimmt. Bei 29 kommt es durch Lokalisation der positiven Ladung nahe der Ether Funktion formal zu einer Kettenverk{\"u}rzung um eine „Methyleneinheit", welche schließlich in h{\"o}heren ET Geschwindigkeiten resultiert. Im dritten Teil dieser Dissertation wurde ein Serie „molekularer Dr{\"a}hte" bestehend aus Methoxy- oder Chlorid-substituierten Triarylamin- und Phenothiazinverbindungen mit unterschiedlichen Br{\"u}ckeneinheiten und Br{\"u}ckenl{\"a}ngen zwischen Redoxzentrum und Ankerfunktion dargestellt und im Hinblick auf ihr ET Verhalten untersucht. Durch cyclovoltammetrische und UV/Vis-spektroskopische Untersuchungen konnte gezeigt werden, dass sowohl die Oxidationspotentiale als auch die energetischen Zust{\"a}nde der Chromophore recht gut durch Einf{\"u}hrung unterschiedlicher Redoxzentren und Br{\"u}ckeneinheiten beeinflusst werden k{\"o}nnen. Trotz erfolgreicher Kontrolle der Dichte der Chromophoreinheiten in den gemischten Monolagen konnte nur f{\"u}r die Verbindungen 49, 52 und 87 mit Nitril-substituierten Br{\"u}ckeneinheiten verl{\"a}ssliche ET Geschwindigkeiten erhalten werden. Bei diesen Chromphoren ist ein Absinken der ET Geschwindigkeit bei zunehmender Dichte der redoxaktiven Molek{\"u}le in den gemischten Monolagen zu beobachten, welche auf eine {\"A}nderung der Adsorptionsgeometrie hindeutet. Bei zunehmender Packungsdichte der Chromophore f{\"u}hrt dies zu einer aufrechteren Stellung der redoxaktiven Spezies. F{\"u}r alle anderen Verbindungen konnten keine Werte aufgrund der zu schnellen ET Geschwindigkeiten ermittelt werden. Konformelle, wie auch die sehr geringe Abstandsabh{\"a}ngigkeit des ET, resultieren in hohen ET Geschwindigkeiten oder auch ung{\"u}nstige HOMO-LUMO Energien bez{\"u}glich des Donors, der Br{\"u}cke und der Elektrode sind Gr{\"u}nde f{\"u}r dieses Verhalten. Die Tatsache, dass Verbindung 49 und 52 beinahe die gleichen Geschwindigkeitskonstanten des ETs unabh{\"a}ngig von der Anzahl der Br{\"u}ckeneinheiten (n = 2, n = 3) besitzen, deutet darauf hin, dass ein Hopping-Prozess stattfindet, bei welchem eine geringere L{\"a}ngenabh{\"a}ngigkeit des ETs als bei eine Superexchange-Mechanismus zu erwarten ist.}, subject = {Monoschicht}, language = {en} } @article{KrausGrimmSeibel2018, author = {Kraus, Michael and Grimm, Clemens and Seibel, J{\"u}rgen}, title = {Reversibility of a Point Mutation Induced Domain Shift: Expanding the Conformational Space of a Sucrose Phosphorylase}, series = {Scientific Reports}, volume = {8}, journal = {Scientific Reports}, doi = {10.1038/s41598-018-28802-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224845}, year = {2018}, abstract = {Despite their popularity as enzyme engineering targets structural information about Sucrose Phosphorylases remains scarce. We recently clarified that the Q345F variant of Bifidobacterium adolescentis Sucrose Phosphorylase is able to accept large polyphenolic substrates like resveratrol via a domain shift. Here we present a crystal structure of this variant in a conformation suitable for the accommodation of the donor substrate sucrose in excellent agreement with the wild type structure. Remarkably, this conformation does not feature the previously observed domain shift which is therefore reversible and part of a dynamic process rather than a static phenomenon. This crystallographic snapshot completes our understanding of the catalytic cycle of this useful variant and will allow for a more rational design of further generations of Sucrose Phosphorylase variants.}, language = {en} } @phdthesis{Kraus2020, author = {Kraus, Michael}, title = {The Conversion of Bifidobacterium adolescentis Sucrose Phosphorylase into a Polyphenol Transglucosidase via Structure-based Enzyme Engineering}, doi = {10.25972/OPUS-19247}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192477}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2020}, abstract = {The initial goal was the conversion of Bifidobacterium adolescentis Sucrose Phosphorylase (BaSP) into a polyphenol glucosidase by structure based enzyme engineering. BaSP was chosen because of its ability to utilize sucrose, an economically viable and sustainable donor substrate, and transfer the glucosyl moiety to various acceptor substrates. The introduction of aromatic residues into the active site was considered a viable way to render it more suitable for aromatic acceptor compounds by reducing its polarity and potentially introducing π-π-interactions with the polyphenols. An investigation of the active site revealed Gln345 as a suitable mutagenesis target. As a proof of concept BaSP Q345F was employed in the glycosylation of (+)-catechin, (-)-epicatechin and resveratrol. The variant was selective for the aromatic acceptor substrates and the glucose disaccharide side reaction was only observed after almost quantitative conversion of the aromatic substrates. A crystal structure of BaSP Q345F in complex with glucose was obtained and it displayed an unexpected shift of an entire domain by 3.3 {\AA}. A crystal structure of BaSP D192N-Q345F, an inactive variant in complex with resveratrol-3-α-D-glucosid, the glucosylation product of resveratrol, synthesized by BaSP Q345F was solved. It proved that the domain shift is in fact responsible for the ability of the variant to glycosylate aromatic compounds. Simultaneously a ligand free crystal structure of BaSP Q345F disproved an induced fit effect as the cause of the domain shift. The missing link, a crystal structure of BaSP Q345F in the F-conformation is obtained. This does not feature the domain shift, but is in outstanding agreement with the wildtype structure. The domain shift is therefore not static but rather a step in a dynamic process. It is further conceivable that the domain shifted conformation of BaSP Q345F resembles the open conformation of the wild type and that an adjustment of a conformational equilibrium as a result of the Q345F point mutation is observed. An investigation into the background reaction, the formation of glucose-glucose disaccharides of BaSP Q345F and three further variants that addressed the same region (L341C, D316C-L341C and D316C-N340C) revealed the formation of nigerose by BaSP Q345F.}, subject = {Phosphorylase}, language = {en} } @article{KraftStanglKrauseetal.2017, author = {Kraft, Andreas and Stangl, Johannes and Krause, Ana-Maria and M{\"u}ller-Buschbaum, Klaus and Beuerle, Florian}, title = {Supramolecular frameworks based on [60]fullerene hexakisadducts}, series = {Beilstein Journal of Organic Chemistry}, volume = {13}, journal = {Beilstein Journal of Organic Chemistry}, doi = {10.3762/bjoc.13.1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171996}, pages = {1-9}, year = {2017}, abstract = {[60]Fullerene hexakisadducts possessing 12 carboxylic acid side chains form crystalline hydrogen-bonding frameworks in the solid state. Depending on the length of the linker between the reactive sites and the malonate units, the distance of the [60]fullerene nodes and thereby the spacing of the frameworks can be controlled and for the most elongated derivative, continuous channels are obtained within the structure. Stability, structural integrity and porosity of the material were investigated by powder X-ray diffraction, thermogravimetry and sorption measurements.}, language = {en} } @article{KorthMuellerSustmannetal.1987, author = {Korth, H.-G. and M{\"u}ller, W. and Sustmann, R. and Christl, Manfred}, title = {Rearrangement of Free Radicals, XII. ESR Spectroscopic Study of the Ring Opening of the Homobenzvalenyl Radical}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58376}, year = {1987}, abstract = {Abstraction of an allylic hydrogen atom in homobenzvalene (4) either in solurion by photolyticaßy generated tert-butoxyl radicals or in an adamantane matrix by X-rays produces the homobcnzvalenyl radical (5). which tbennally rearranps · to tbe tropylium ndical (1). In solution tbe activation cnergy for the rate determined step of the reaction sequence was detennined· to be 13.4 ± O.S kcal/mol.}, subject = {Organische Chemie}, language = {en} } @article{KoleKošćakAmaretal.2022, author = {Kole, Goutam Kumar and Košćak, Marta and Amar, Anissa and Majhen, Dragomira and Božinović, Ksenija and Brkljaca, Zlatko and Ferger, Matthias and Michail, Evripidis and Lorenzen, Sabine and Friedrich, Alexandra and Krummenacher, Ivo and Moos, Michael and Braunschweig, Holger and Boucekkine, Abdou and Lambert, Christoph and Halet, Jean-Fran{\c{c}}ois and Piantanida, Ivo and M{\"u}ller-Buschbaum, Klaus and Marder, Todd B.}, title = {Methyl Viologens of Bis-(4'-Pyridylethynyl)Arenes - Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology}, series = {Chemistry - A European Journal}, volume = {28}, journal = {Chemistry - A European Journal}, number = {40}, doi = {10.1002/chem.202200753}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287126}, year = {2022}, abstract = {A series of bis-(4'-pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis-N-methylpyridinium compounds were investigated as a class of π-extended methyl viologens. Their structures were determined by single crystal X-ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis-N-methylpyridinium compound showed a larger two-photon absorption cross-section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds-DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene-analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi-faceted features, in combination with its two-photon absorption properties, suggest it to be a promising lead compound for development of novel light-activated theranostic agents.}, language = {en} } @article{KokicHillenTegunovetal.2021, author = {Kokic, Goran and Hillen, Hauke S. and Tegunov, Dimitry and Dienermann, Christian and Seitz, Florian and Schmitzova, Jana and Farnung, Lucas and Siewert, Aaron and H{\"o}bartner, Claudia and Cramer, Patrick}, title = {Mechanism of SARS-CoV-2 polymerase stalling by remdesivir}, series = {Nature Communications}, volume = {12}, journal = {Nature Communications}, doi = {10.1038/s41467-020-20542-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220979}, year = {2021}, abstract = {Remdesivir is the only FDA-approved drug for the treatment of COVID-19 patients. The active form of remdesivir acts as a nucleoside analog and inhibits the RNA-dependent RNA polymerase (RdRp) of coronaviruses including SARS-CoV-2. Remdesivir is incorporated by the RdRp into the growing RNA product and allows for addition of three more nucleotides before RNA synthesis stalls. Here we use synthetic RNA chemistry, biochemistry and cryoelectron microscopy to establish the molecular mechanism of remdesivir-induced RdRp stalling. We show that addition of the fourth nucleotide following remdesivir incorporation into the RNA product is impaired by a barrier to further RNA translocation. This translocation barrier causes retention of the RNA 3ʹ-nucleotide in the substrate-binding site of the RdRp and interferes with entry of the next nucleoside triphosphate, thereby stalling RdRp. In the structure of the remdesivir-stalled state, the 3ʹ-nucleotide of the RNA product is matched and located with the template base in the active center, and this may impair proofreading by the viral 3ʹ-exonuclease. These mechanistic insights should facilitate the quest for improved antivirals that target coronavirus replication.}, language = {en} } @phdthesis{Klein2015, author = {Klein, Johannes Hubert}, title = {Electron Transfer and Spin Chemistry in Iridium-Dipyrrin Dyads and Triads}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-118726}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {The successful synthesis of a family of donor-iridium complex-acceptor triads (T1-T6, pMV1 and mMV1) and their electrochemical and photophysical properties were presented in this work. Triarylamines (TAA) were used as donors and naphthalene diimide (NDI) as acceptor. A bis-cyclometalated phenylpyrazole iridium dipyrrin complex acts as a photosensitiser. In addition, a molecular structure of T1 was obtained by single crystal X-ray diffraction. Transient absorption spectroscopy experiments of these triads resembled that upon excitation a photoinduced electron transfer efficiently generates long-lived, charge-separated (CS) states. Thereby, the electron-transfer mechanism depends on the excitation energy. The presence of singlet and triplet CS states was clarified by magnetic-field dependent transient-absorption spectroscopy in the nanosecond time regime. It was demonstrated that the magnetic field effect of charge-recombination kinetics showed for the first time a transition from the coherent to the incoherent spin-flip regime. The lifetime of the CS states could be drastically prolonged by varying the spacer between the iridium complex and the NDI unit by using a biphenyl instead of a phenylene unit in T4. A mixed-valence (MV) state of two TAA donors linked to an iridium metal centre were generated upon photoexcitation of triad pMV1 and mMV1. The mixed-valence character in these triads was proven by the analysis of an intervalence charge-transfer (IV-CT) band in the (near-infrared) NIR spectral region by femtosecond pump-probe experiments. These findings were supported by TD-DFT calculations. The synthesis of dyads (D1-D4) was performed. Thereby the dipyrrin ligand was substituted with electron withdrawing groups. The electrochemical and photophysical characterisation revealed that in one case (D4) it was possible to generate a CS state upon photoexcitation.}, subject = {Elektronentransfer}, language = {en} } @article{KleiberLemusDiazStilleretal.2022, author = {Kleiber, Nicole and Lemus-Diaz, Nicolas and Stiller, Carina and Heinrichs, Marleen and Mong-Quyen Mai, Mandy and Hackert, Philipp and Richter-Dennerlein, Ricarda and H{\"o}bartner, Claudia and Bohnsack, Katherine E. and Bohnsack, Markus T.}, title = {The RNA methyltransferase METTL8 installs m\(^3\)C\(_{32}\) in mitochondrial tRNAs\(^{Thr/Ser(UCN)}\) to optimise tRNA structure and mitochondrial translation}, series = {Nature Communication}, volume = {13}, journal = {Nature Communication}, doi = {10.1038/s41467-021-27905-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254592}, year = {2022}, abstract = {Modified nucleotides in tRNAs are important determinants of folding, structure and function. Here we identify METTL8 as a mitochondrial matrix protein and active RNA methyltransferase responsible for installing m\(^3\)C\(_{32}\) in the human mitochondrial (mt-)tRNA\(^{Thr}\) and mt-tRNA\(^{Ser(UCN)}\). METTL8 crosslinks to the anticodon stem loop (ASL) of many mt-tRNAs in cells, raising the question of how methylation target specificity is achieved. Dissection of mttRNA recognition elements revealed U\(_{34}\)G\(_{35}\) and t\(^6\)A\(_{37}\)/(ms\(^2\))i\(^6\)A\(_{37}\), present concomitantly only in the ASLs of the two substrate mt-tRNAs, as key determinants for METTL8-mediated methylation of C\(_{32}\). Several lines of evidence demonstrate the influence of U\(_{34}\), G\(_{35}\), and the m\(^3\)C\(_{32}\) and t\(^6\)A\(_{37}\)/(ms\(^2\))i\(^6\)A\(_{37}\) modifications in mt-tRNA\(^{Thr/Ser(UCN)}\) on the structure of these mt-tRNAs. Although mt-tRNA\(^{Thr/Ser(UCN)}\) lacking METTL8-mediated m\(^3\)C\(_{32}\) are efficiently aminoacylated and associate with mitochondrial ribosomes, mitochondrial translation is mildly impaired by lack of METTL8. Together these results define the cellular targets of METTL8 and shed new light on the role of m\(^3\)C\(_{32}\) within mt-tRNAs.}, language = {en} } @article{KirchnerSchrammIvanovaetal.2024, author = {Kirchner, Philipp H. and Schramm, Louis and Ivanova, Svetlana and Shoyama, Kazutaka and W{\"u}rthner, Frank and Beuerle, Florian}, title = {A water-stable boronate ester cage}, series = {Journal of the American Chemical Society}, volume = {146}, journal = {Journal of the American Chemical Society}, number = {8}, issn = {0002-7863}, doi = {10.1021/jacs.3c12002}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-361245}, pages = {5305-5315}, year = {2024}, abstract = {The reversible condensation of catechols and boronic acids to boronate esters is a paradigm reaction in dynamic covalent chemistry. However, facile backward hydrolysis is detrimental for stability and has so far prevented applications for boronate-based materials. Here, we introduce cubic boronate ester cages 6 derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding, dynamic exchange at the Lewis acidic boron sites is feasible only under acid or base catalysis but fully prevented at neutral conditions. For the first time, boronate ester cages 6 tolerate substantial amounts of water or alcohols both in solution and solid state. The unprecedented applicability of these materials under ambient and aqueous conditions is showcased by efficient encapsulation and on-demand release of β-carotene dyes and heterogeneous water oxidation catalysis after the encapsulation of ruthenium catalysts.}, language = {en} } @phdthesis{Kirchner2019, author = {Kirchner, Eva}, title = {Discrete Supramolecular Stacks by Self-Assembly and Folding of Bis(merocyanine) Dyes}, doi = {10.25972/OPUS-15941}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159419}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2019}, abstract = {The present thesis describes the development of a strategy to create discrete finite-sized supramolecular stacks of merocyanine dyes. Thus, bichromophoric stacks of two identical or different chromophores could be realized by folding of bis(merocyanine) dyes and their optical properties were discussed in terms of exciton theory. Quantum chemical calculations revealed strong exciton coupling between the chromophores within the homo- and hetero-π-stacks and the increase of the J-band of the hetero-dimers with increasing energy difference between the excited states of the chromophores could be attributed not only to the different magnitudes of transition dipole moments of the chromophores but also to the increased localization of the excitation in the respective exciton state. Furthermore, careful selection of the length of the spacer unit that defines the interplanar distance between the tethered chromophores directed the self-assembly of the respective bis(merocyanines) into dimers, trimers and tetramers comprising large, structurally precise π-stacks of four, six or eight merocyanine chromophores. It could be demonstrated that the structure of such large supramolecular architectures can be adequately elucidated by commonly accessible analysis tools, in particular NMR techniques in combination with UV/vis measurements and mass spectrometry. Supported by TDDFT calculations, the absorption spectra of the herein investigated aggregates could be explained and a relationship between the absorption properties and the number of stacking chromophores could be established based on exciton theory.}, subject = {Merocyanine}, language = {en} } @phdthesis{KimbadiLombe2021, author = {Kimbadi Lombe, Blaise}, title = {Novel-Type Dimeric Naphthylisoquinoline Alkaloids from Congolese Ancistrocladus Lianas: Isolation, Structural Elucidation, and Antiprotozoal and Anti-Tumoral Activities}, doi = {10.25972/OPUS-19178}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191789}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Herein described is the discovery of three novel types of dimeric naphthylisoquinoline alkaloids, named mbandakamines, cyclombandakamines, and spirombandakamines. They were found in the leaves of a botanically as yet unidentified, potentially new Ancistrocladus species, collected in the rainforest of the Democratic Republic of the Congo (DRC). Mbandakamines showed an exceptional 6′,1′′-coupling, in the peri-position neighboring one of the outer axes, leading to an extremely high steric hindrance at the central axis, and to U-turn-like molecular shape, which - different from all other dimeric NIQs, whose basic structures are all quite linear - brings three of the four bicyclic ring systems in close proximity to each other. This created an unprecedented follow-up chemistry, involving ring closure reactions, leading to two further, structurally even more intriguing subclasses, the cyclo- and the spirombandakamines, displaying eight stereogenic elements (the highest total number ever found in naphthylisoquinoline alkaloids). The metabolites exhibited pronounced antiplasmodial and antitrypanosomal activities. Likewise reported in this doctoral thesis are the isolation and structural elucidation of naphthylisoquinoline alkaloids from two further potentially new Ancistrocladus species from DRC. Some of these metabolites have shown pronounced antiausterity activities against human pancreatic cancer PANC-1 cells.}, subject = {Naphthylisochinolinalkaloide}, language = {en} } @article{KimSchembriBialasetal.2022, author = {Kim, Jin Hong and Schembri, Tim and Bialas, David and Stolte, Matthias and W{\"u}rthner, Frank}, title = {Slip-Stacked J-Aggregate Materials for Organic Solar Cells and Photodetectors}, series = {Advanced Materials}, volume = {34}, journal = {Advanced Materials}, number = {22}, doi = {10.1002/adma.202104678}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-276537}, year = {2022}, abstract = {Dye-dye interactions affect the optical and electronic properties in organic semiconductor films of light harvesting and detecting optoelectronic applications. This review elaborates how to tailor these properties of organic semiconductors for organic solar cells (OSCs) and organic photodiodes (OPDs). While these devices rely on similar materials, the demands for their optical properties are rather different, the former requiring a broad absorption spectrum spanning from the UV over visible up to the near-infrared region and the latter an ultra-narrow absorption spectrum at a specific, targeted wavelength. In order to design organic semiconductors satisfying these demands, fundamental insights on the relationship of optical properties are provided depending on molecular packing arrangement and the resultant electronic coupling thereof. Based on recent advancements in the theoretical understanding of intermolecular interactions between slip-stacked dyes, distinguishing classical J-aggregates with predominant long-range Coulomb coupling from charge transfer (CT)-mediated or -coupled J-aggregates, whose red-shifts are primarily governed by short-range orbital interactions, is suggested. Within this framework, the relationship between aggregate structure and functional properties of representative classes of dye aggregates is analyzed for the most advanced OSCs and wavelength-selective OPDs, providing important insights into the rational design of thin-film optoelectronic materials.}, language = {en} } @article{KimLiessStolteetal.2021, author = {Kim, Jin Hong and Liess, Andreas and Stolte, Matthias and Krause, Ana-Maria and Stepanenko, Vladimir and Zhong, Chuwei and Bialas, David and Spano, Frank and W{\"u}rthner, Frank}, title = {An Efficient Narrowband Near-Infrared at 1040 nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye}, series = {Advanced Materials}, volume = {33}, journal = {Advanced Materials}, number = {26}, doi = {10.1002/adma.202100582}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256374}, year = {2021}, abstract = {A highly sensitive short-wave infrared (SWIR, λ > 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC\(_{61}\)BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3\% and a full-width at half-maximum of only 85 nm (815 cm\(^{-1}\)) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.}, language = {en} } @article{KimChristlKochl1990, author = {Kim, E. and Christl, Manfred and Kochl, J. K.}, title = {Charge-Transfer Cycloaddition of Homobenzvalene with Tetracyanoethylene}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58537}, year = {1990}, abstract = {The transient yellow color observed in the cycloaddition of homobenzvalene (HB) with tetracyanoethylene (TCNE) is associated with the charge-transfer complex [HB, TCNE). The deliberate photoexcitation of [HB,TCNE) affords a mixture of charge-transfer cycloadducts (1, 2, and 3) that differs from that obtained in thermal cycloaddition. The relationship of {HB t TCNE•) radical-ion pair (as the critical reactive intermediate in charge-transfer cycloaddition) to the activation process for thermal cycloaddition is discussed.}, subject = {Organische Chemie}, language = {en} } @phdthesis{Kiendl2020, author = {Kiendl, Benjamin}, title = {Application of diamond nanomaterials in catalysis}, doi = {10.25972/OPUS-17941}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-179415}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2020}, abstract = {In this work the catalytic activity of nanodiamond particles with different dopants and surface terminations and of diamond nanomaterials funtionalized with ruthenium-based photocatalysts was investigated, illustrating materials application in photoredox chemistry and the photo(electro)catalytic reduction of CO2. Regarding the application of diamond nanomaterials in photocatalysis, methods to fabricate and characterize several (un)doped nanoparticles with different surface termination were successfully developed. Various photocatalysts, attached to nanodiamond particles via linker systems, were tested in photoredox catalysis and the photo(electro)catalytic reduction of CO2.}, subject = {Fotokatalyse}, language = {en} } @article{KauppSchleyer1992, author = {Kaupp, Martin and Schleyer, Paul von Rague}, title = {Do Low-Coordinated Group 1-3 cations M\(^n\) \(^+\)L\(_m\) (Mn\(^+\) = K\(^+\), Rb\(^+\), Cs\(^+\), Ca\(^{2+}\), Sr\(^{2+}\), Ba\(^{2+}\), Sc\(^{3+}\), Y\(^{3+}\), La\(^{3+}\); L = NH\(_3\), H\(_2\)0, HF; m = 1-3) with a Formal Noble-Gas Electron Configuration Favor Regular or "Abnormal" Shapes?}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60111}, year = {1992}, abstract = {No abstract available}, subject = {Anorganische Chemie}, language = {en} } @phdthesis{Kaufmann2019, author = {Kaufmann, Christina}, title = {Discrete Supramolecular Architectures of Bay-linked Perylene Bisimide Dimers by Self-Assembly and Folding}, doi = {10.25972/OPUS-17300}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173005}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2019}, abstract = {Supramolecular self-assembly of perylene bisimide (PBI) dyes via non-covalent forces gives rise to a high number of different PBI architectures with unique optical and functional properties. As these properties can be drastically influenced by only slightly structural changes of the formed supramolecular ensembles (Chapter 2.1) the controlled self-assembly of PBI dyes became a central point of current research to design innovative materials with a high potential for different applications as for example in the fields of organic electronics or photovoltaics. As PBI dyes show a strong tendency to form infinite aggregated structures (Chapter 2.2) the aim of this thesis was to precisely control their self-assembly to create small, structurally well-defined PBI assemblies in solution. Chapter 2.3 provides an overview on literature known strategies that were established to realize this aim. It could be demonstrated that especially backbone-directed intra- and intermolecular self-assembly of covalently linked Bis-PBI dyes evolved as one of the most used strategies to define the number of stacked PBI chromophores by using careful designed spacer units with regard to their length and flexibility. By using conventional spectroscopic methods like UV/Vis and fluorescence experiments in combination with NMR measurements an in-depth comparison of the molecular and optical properties in solution both in the non-stacked and aggregated state of the target compounds could be elucidated to reveal structure-property relationships of different PBI architectures. Thus, it could be demonstrated, that spacer units that pre-organize two PBI chromophores with an inter-planar distance of r < 7 {\AA} lead to an intramolecular folding, whereas linker moieties with a length between 7 to 11 {\AA} result in an intermolecular self-assembly of the respective Bis-PBIs dyes via dimerization to form well-defined quadruple PBI pi-stacks. Hence, if the used spacer units ensure an inter-planar distance r > 14 {\AA} larger oligomeric PBI pi-stacks are generated. In Chapter 4 a detailed analysis of the exciton coupling in a highly defined H-aggregate quadruple PBI pi-stack is presented. Therefore, bay-tethered PBI dye Bis-PBI 1 was investigated by concentration-dependent UV/Vis spectroscopy in THF and toluene as well as by 2D-DOSY-NMR spectroscopy, ESI mass spectrometry and AFM measurements confirming that Bis-PBI 1 self-assembles exclusively into dimers with four closely pi-stacked PBI chromophores. Furthermore, with the aid of broadband fluorescence upconversion spectroscopy (FLUPS) ensuring broadband detection range and ultrafast time resolution at once, ultrafast Frenkel exciton relaxation and excimer formation dynamics in the PBI quadruple pi-stack within 1 ps was successfully investigated in cooperation with the group of Dongho Kim. Thus, it was possible to gain for the first time insights into the exciton dynamics within a highly defined synthetic dye aggregate beyond dimers. By analysing the vibronic line shape in the early-time transient fluorescence spectra in detail, it could be demonstrated that the Frenkel exciton is entirely delocalized along the quadruple stack after photoexcitation and immediately loses its coherence followed by the formation of the excimer state. In Chapter 5 four well-defined Bis-PBI folda-dimers Bis-PBIs 2-4 were introduced, where linker units of different length (r < 7 {\AA}) and steric demand were used to gain distinct PBI dye assemblies in the folded state. Structural elucidation based on in-depth UV/Vis, CD and fluorescence experiments in combination with 1D and 2D NMR studies reveals a stacking of the two PBI chromophores upon folding, where geometry-optimized structures obtained from DFT calculations suggest only slightly different arrangements of the PBI units enforced by the distinct spacer moieties. With the resulting optical signatures of Bis-PBIs 2-4 ranging from conventional Hj-type to monomer like absorption features, the first experimental proof of a PBI-based "null-aggregate" could be presented, in which long- and short-range exciton coupling fully compensate each other. Hence, the insights of this chapter pinpoint the importance of charge-transfer mediated short-range exciton coupling that can significantly influence the properties of pi-stacked PBI chromophores In the last part of this thesis (Chapter 6), spacer-controlled self-assembly of four bay-linked Bis-PBI dyes Bis-PBIs 5-8 into well-defined supramolecular architectures was investigated, where the final aggregate structures are substantially defined by the nature of the used spacer units. By systematically extending the backbone length from 7 to 15 {\AA} defining the inter-planar distance between the tethered chromophores, different assemblies from defined quadruple PBI pi-stacks to larger oligomeric pi-stacks could be gained upon aggregation. In conclusion, the synthesis of nine covalently linked PBI dyes in combination with a detailed investigation of their spacer-mediated self-assembly behaviour in solution concerning structure-properties-relationships was presented within this thesis. The results confirm a strong exciton coupling in different types of Bis-PBI architectures e.g. folda-dimers or highly defined quadruple pi-stacks, which significantly influences their optical properties upon self-assembly.}, subject = {Supramolekulare Chemie}, language = {en} } @article{KarnaGreinEngelsetal.1990, author = {Karna, S.P. and Grein, F. and Engels, Bernd and Peyerimhoff, S.D.}, title = {Ab initio configuration-interaction studies of the ground state potential energy and hyperfine coupling constants of \(^{35}\)Cl\(_2^-\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58869}, year = {1990}, abstract = {Potential energy and spectroscopic constants for the X\(^2 \sum^+ _\mu\) ground state of a;, were calculated by configuration-interaction (Cl) methods, using large basis sets with polarization and diffuse functions. From these CI wavefunctions, the isotropic (a\(_{iso}\)) and dipolar (A\(_{dip}\)) components of the hyperfine coupling constant were obtained. The effects of various s, p basis sets, polarization and diffuse functions, as well as the influence of reference configurations and configuration selection thresholds were investigated. The best values obtained are 35·31 G for a\(_{iso}\) and 29·440 for A\(_{dip}\)• tobe compared with experimental values of 37 ± 1 G and 32 ± 1 G, respectively. It is shown that the contributions to a1so of the K and L shells are opposite in sign, differing by about 4 G. Upon vibrational averaging, both a\(_{iso}\) and A\(_{dip}\) move towards smaller values as v increases. An adiabatic electron affinity of 2·46eV was obtained for CL\(_2\) , and a vertical electron detachment energy of 3·71 eV for Cl;.}, subject = {Organische Chemie}, language = {en} } @article{KarnaGreinEngelsetal.1989, author = {Karna, S. and Grein, F. and Engels, Bernd and Peyerimhoff, S.D.}, title = {The hyperfine coupling constants of \(^{19}\)F\(_2\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58817}, year = {1989}, abstract = {The isotropic (a\(_{iso}\)) and dipolar (A\(_{dip}\)) hyperfine coupling constants of 19F2 were obtained from MRD-CI wave functions using a variety of basis sets. In series I, increasing numbers of d functions were added to a 5s4p contracted Huzinaga!Dunning basis. In series II, the 5s3p basis set was uncontracted in several steps until 9s5p was reached, to which were added from one to three d-polarization functions. Cl parameters (selectioo threshoids and the number of reference coofiguratioos) were also varied. A study of the R dependence of aiso and Adip was perfonned. The best values obtained at R\(_e\) are 260 G for a\(_{iso}\) and 308 G for A\(_{dip}\)• compared with experimental values of about 280 G for a;10 and 320 G for A\(_{dip}\)·}, subject = {Organische Chemie}, language = {en} } @article{KarakStepanenkoAddicoatetal.2022, author = {Karak, Suvendu and Stepanenko, Vladimir and Addicoat, Matthew A. and Keßler, Philipp and Moser, Simon and Beuerle, Florian and W{\"u}rthner, Frank}, title = {A Covalent Organic Framework for Cooperative Water Oxidation}, series = {Journal of the American Chemical Society}, volume = {144}, journal = {Journal of the American Chemical Society}, number = {38}, issn = {0002-7863}, doi = {10.1021/jacs.2c07282}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287591}, pages = {17661-17670}, year = {2022}, abstract = {The future of water-derived hydrogen as the "sustainable energy source" straightaway bets on the success of the sluggish oxygen-generating half-reaction. The endeavor to emulate the natural photosystem II for efficient water oxidation has been extended across the spectrum of organic and inorganic combinations. However, the achievement has so far been restricted to homogeneous catalysts rather than their pristine heterogeneous forms. The poor structural understanding and control over the mechanistic pathway often impede the overall development. Herein, we have synthesized a highly crystalline covalent organic framework (COF) for chemical and photochemical water oxidation. The interpenetrated structure assures the catalyst stability, as the catalyst's performance remains unaltered after several cycles. This COF exhibits the highest ever accomplished catalytic activity for such an organometallic crystalline solid-state material where the rate of oxygen evolution is as high as ∼26,000 μmol L\(^{-1}\) s\(^{-1}\) (second-order rate constant k ≈ 1650 μmol L s\(^{-1}\) g\(^{-2}\)). The catalyst also proves its exceptional activity (k ≈ 1600 μmol L s\(^{-1}\) g\(^{-2}\)) during light-driven water oxidation under very dilute conditions. The cooperative interaction between metal centers in the crystalline network offers 20-30-fold superior activity during chemical as well as photocatalytic water oxidation as compared to its amorphous polymeric counterpart.}, language = {en} } @article{KarGehrigAllampallyetal.2016, author = {Kar, Haridas and Gehrig, Dominik W. and Allampally, Naveen Kumar and Fern{\´a}ndez, Gustavo and Laquai, Fr{\´e}d{\´e}ric and Ghosh, Suhrit}, title = {Cooperative supramolecular polymerization of an amine-substituted naphthalene-diimide and its impact on excited state photophysical properties}, series = {Chemical Science}, volume = {7}, journal = {Chemical Science}, number = {2}, doi = {10.1039/c5sc03462k}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191459}, pages = {1115-1120}, year = {2016}, abstract = {A donor-acceptor-donor (D-A-D) type naphthalene-diimide (NDI-H) chromophore exhibits highly cooperative J-aggregation leading to nanotubular self-assembly and gelation in n-decane, as demonstrated by UV/Vis, FT-IR, photoluminescence and microscopy studies. Analysis of temperature-dependent UV/Vis spectra using the nucleation-elongation model and FT-IR data reveals the molecular origin of the cooperative nature of the self-assembly. The supramolecular polymerization is initiated by H-bonding up to a degree of polymerization similar to 20-25, which in a subsequent elongation step promotes J-aggregation in orthogonal direction leading to possibly a sheet-like structure that eventually produces nanotubes. Time-resolved fluorescence and absorption measurements demonstrate that such a tubular assembly enables very effective delocalization of excited states resulting in a remarkably prolonged excited state lifetime.}, language = {en} } @phdthesis{Kaiser2009, author = {Kaiser, Theo E.}, title = {J-Aggregates of Tetraphenoxy-Substituted Perylene Bisimide Dyes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-43544}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2009}, abstract = {In dieser Doktorarbeit wurde gezeigt, dass die sehr begehrte J-Aggregation funktionaler Perylenbisimid-Chromophore durch geeignetes Design der monomeren Bausteine erreicht werden kann. Hierzu war einerseits die Selbstanordnung durch ein Zusammenwirken von Wasserstoffbr{\"u}cken und Pi-Pi-Wechselwirkungen zu beg{\"u}nstigen, und andererseits eine Anordnung in kolumnaren Stapeln zu verhindern, was durch Kern-Verdrillung mittels sterisch anspruchsvollen Substituenten gelang. Desweiteren gaben Selbstanordnungsstudien neue Einblicke in den dynamischen Aggregationsprozess niedrigdimensionaler langgestreckter Aggregate mit stark exzitonisch gekoppelten Chromophoren. Die Beziehung zwischen bekannten Cyaninfarbstoffen, wie der von THIATS mit dem vorliegenden PBI 1a wurde durch Absorptions- und Fluoreszenzspektroskopie bei Tieftemperaturen von 5 K bis Raumtemperatur untersucht. Die vormals beispiellosen funktionalen Eigenschaften der PBI-Aggregate, welche aus der J-artigen exzitonischen Kopplung herr{\"u}hren, sind vielversprechend f{\"u}r die Anwendung in optoelektronischen Bauteilen und f{\"u}r die Photovoltaik.}, subject = {Perylenbisdicarboximide