TY - JOUR A1 - Hoernes, Thomas Philipp A1 - Faserl, Klaus A1 - Juen, Michael Andreas A1 - Kremser, Johannes A1 - Gasser, Catherina A1 - Fuchs, Elisabeth A1 - Shi, Xinying A1 - Siewert, Aaron A1 - Lindner, Herbert A1 - Kreutz, Christoph A1 - Micura, Ronald A1 - Joseph, Simpson A1 - Höbartner, Claudia A1 - Westhof, Eric A1 - Hüttenhofer, Alexander A1 - Erlacher, Matthias David T1 - Translation of non-standard codon nucleotides reveals minimal requirements for codon-anticodon interactions JF - Nature Communications N2 - The precise interplay between the mRNA codon and the tRNA anticodon is crucial for ensuring efficient and accurate translation by the ribosome. The insertion of RNA nucleobase derivatives in the mRNA allowed us to modulate the stability of the codon-anticodon interaction in the decoding site of bacterial and eukaryotic ribosomes, allowing an in-depth analysis of codon recognition. We found the hydrogen bond between the N1 of purines and the N3 of pyrimidines to be sufficient for decoding of the first two codon nucleotides, whereas adequate stacking between the RNA bases is critical at the wobble position. Inosine, found in eukaryotic mRNAs, is an important example of destabilization of the codon-anticodon interaction. Whereas single inosines are efficiently translated, multiple inosines, e.g., in the serotonin receptor 5-HT2C mRNA, inhibit translation. Thus, our results indicate that despite the robustness of the decoding process, its tolerance toward the weakening of codon-anticodon interactions is limited. KW - chemical modification KW - nucleic acids KW - ribozymes KW - RNA Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-321067 VL - 9 ER - TY - JOUR A1 - Herbst, Stefanie A1 - Soberats, Bartolome A1 - Leowanawat, Pawaret A1 - Stolte, Matthias A1 - Lehmann, Matthias A1 - Würthner, Frank T1 - Self-assembly of multi-stranded perylene dye J-aggregates in columnar liquid-crystalline phases JF - Nature Communications N2 - Many discoid dyes self-assemble into columnar liquid-crystalline (LC) phases with packing arrangements that are undesired for photonic applications due to H-type exciton coupling. Here, we report a series of crystalline and LC perylene bisimides (PBIs) self-assembling into single or multi-stranded (two, three, and four strands) aggregates with predominant J-type exciton coupling. These differences in the supramolecular packing and optical properties are achieved by molecular design variations of tetra-bay phenoxy-dendronized PBIs with two N–H groups at the imide positions. The self-assembly is driven by hydrogen bonding, slipped π–π stacking, nanosegregation, and steric requirements of the peripheral building blocks. We could determine the impact of the packing motifs on the spectroscopic properties and demonstrate different J- and H-type coupling contributions between the chromophores. Our findings on structure–property relationships and strong J-couplings in bulk LC materials open a new avenue in the molecular engineering of PBI J-aggregates with prospective applications in photonics. KW - liquid crystals KW - self-assembly Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-319914 VL - 9 ER - TY - JOUR A1 - Gil-Sepulcre, Marcos A1 - Lindner, Joachim O. A1 - Schindler, Dorothee A1 - Velasco, Lucía A1 - Moonshiram, Dooshaye A1 - Rüdiger, Olaf A1 - DeBeer, Serena A1 - Stepanenko, Vladimir A1 - Solano, Eduardo A1 - Würthner, Frank A1 - Llobet, Antoni T1 - Surface-promoted evolution of Ru-bda coordination oligomers boosts the efficiency of water oxidation molecular anodes JF - Journal of the American Chemical Society N2 - A new Ru oligomer of formula {[Ru-\(^{II}\)(bda-\(\kappa\)-N\(^2\)O\(^2\))(4,4'-bpy)]\(_{10}\)(4,4'-bpy)}, 10 (bda is [2,2'-bipyridine]-6,6'-dicarbox-ylate and 4,4'-bpy is 4,4'-bipyridine), was synthesized and thoroughly characterized with spectroscopic, X-ray, and electrochemical techniques. This oligomer exhibits strong affinity for graphitic materials through CH-\(\pi\) interactions and thus easily anchors on multiwalled carbon nanotubes (CNT), generating the molecular hybrid material 10@CNT. The latter acts as a water oxidation catalyst and converts to a new species, 10'(H\(_2\)O)\(_2\)@CNT, during the electrochemical oxygen evolution process involving solvation and ligand reorganization facilitated by the interactions of molecular Ru catalyst and the surface. This heterogeneous system has been shown to be a powerful and robust molecular hybrid anode for electrocatalytic water oxidation into molecular oxygen, achieving current densities in the range of 200 mA/cm\(^2\) at pH 7 under an applied potential of 1.45 V vs NHE. The remarkable long-term stability of this hybrid material during turnover is rationalized based on the supramolecular interaction of the catalyst with the graphitic surface. KW - electrodes KW - ligands KW - oligomers KW - surface interactions KW - water oxidation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-351514 VL - 143 IS - 30 ER - TY - JOUR A1 - Gryszel, Maciej A1 - Schlossarek, Tim A1 - Würthner, Frank A1 - Natali, Mirco A1 - Głowacki, Eric Daniel T1 - Water‐soluble cationic perylene diimide dyes as stable photocatalysts for H\(_2\)O\(_2\) evolution JF - ChemPhotoChem N2 - Photocatalytic generation of hydrogen peroxide, H\(_2\)O\(_2\), has gained increasing attention in recent years, with applications ranging from solar energy conversion to biophysical research. While semiconducting solid‐state materials are normally regarded as the workhorse for photogeneration of H\(_2\)O\(_2\), an intriguing alternative for on‐demand H\(_2\)O\(_2\) is the use of photocatalytic organic dyes. Herein we report the use of water‐soluble dyes based on perylene diimide molecules which behave as true molecular catalysts for the light‐induced conversion of dissolved oxygen to hydrogen peroxide. In particular, we address how to obtain visible‐light photocatalysts which are stable with respect to aggregation and photochemical degradation. We report on the factors affecting efficiency and stability, including variable electron donors, oxygen partial pressure, pH, and molecular catalyst structure. The result is a perylene diimide derivative with unprecedented peroxide evolution performance using a broad range of organic donor molecules and operating in a wide pH range. KW - hydrogen peroxide KW - oxygen reduction reaction KW - perylene KW - photocatalysis KW - dyes/pigments Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-370250 SN - 2367-0932 VL - 7 IS - 9 ER - TY - JOUR A1 - He, Tao A1 - Wu, Yanfei A1 - D'Avino, Gabriele A1 - Schmidt, Elliot A1 - Stolte, Matthias A1 - Cornil, Jérôme A1 - Beljonne, David A1 - Ruden, P. Paul A1 - Würthner, Frank A1 - Frisbie, C. Daniel T1 - Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors JF - Nature Communications N2 - Understanding relationships between microstructure and electrical transport is an important goal for the materials science of organic semiconductors. Combining high-resolution surface potential mapping by scanning Kelvin probe microscopy (SKPM) with systematic field effect transport measurements, we show that step edges can trap electrons on the surfaces of single crystal organic semiconductors. n-type organic semiconductor crystals exhibiting positive step edge surface potentials display threshold voltages that increase and carrier mobilities that decrease with increasing step density, characteristic of trapping, whereas crystals that do not have positive step edge surface potentials do not have strongly step density dependent transport. A device model and microelectrostatics calculations suggest that trapping can be intrinsic to step edges for crystals of molecules with polar substituents. The results provide a unique example of a specific microstructure–charge trapping relationship and highlight the utility of surface potential imaging in combination with transport measurements as a productive strategy for uncovering microscopic structure–property relationships in organic semiconductors. KW - electronic and spintronic devices KW - electronic devices KW - scanning probe microscopy Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227957 VL - 9 ER - TY - THES A1 - Swain, Asim T1 - Helically Twisted Graphene Nanoribbons: Bottom-up Stereospecific Synthesis and Characterization T1 - Helikal verdrehte Graphen-Nanoribbons: Bottom-up stereospezifische Synthese und Charakterisierung N2 - Over the past decade, substantial progress has been made in synthesizing atomically precise carbon nanostructures, with a focus on graphene nanoribbons (NRs) through advanced synthetic techniques. Despite these advancements, precise control over the stereochemistry of twisted NRs remains challenging. This thesis introduces a strategic approach to achieve absolute control over the single-handed helical conformation in a cove-edged NR, utilizing enantiopure [n]helicenes as a molecular wrench to intricately dictate the overall conformation of the NR. Enantiopure [7]helicenes were stitched to the terminal K-regions of a conjugated pyrene NR using a stereospecific and site-selective palladium(II)-catalyzed annulative π-extension (APEX) reaction, resulting in a helically twisted NR with an end-to-end twist of 171°, the second-largest twist reported so far in the literature for twistacenes. The helical end-to-end twist increases with each addition of benzene ring to the central acene core, suggesting that the extra strain induced by the terminal [7]helicenes maintains such a high level of twist. The quantum chemical calculations were conducted to investigate the impact of twisting on the conformational population. At room temperature, the central backbone of the nanoribbon adopts the twisted helicity opposite to that of the attached [7]helicene, constituting around 99% of the molecular population. For instance, (P)-[7]helicenes produce a left-handed helical nanoribbon, while (M)-[7]helicenes produce a right-handed helical nanoribbon. In the presence of helicenes of opposite chirality, the nanoribbon adopts a waggling conformation. The helically twisted nanoribbons are conformationally robust, as variable temperature chiroptical measurements showed no change in CD and CPL spectra. The proposed strategy, involving the late-stage addition of [n]helicene units through the APEX reaction, appears promising for streamlining the synthesis of diverse cove edge NR variants with desired conformations. In addition to single-handed helically twisted nanoribbons, the symmetry-based functional properties of C2 and C1 symmetric pyrene-fused single and double [n]helicene compounds were studied. Owing to its higher structural rigidity, the C1 symmetric heptagonal ring-containing molecules exhibited exceptional configurational stability along with remarkable chiroptical properties compared to their C2 symmetric as well as pristine helicene congeners. N2 - In den letzten zehn Jahren wurden erhebliche Fortschritte bei der Synthese von atomar präzisen Kohlenstoffnanostrukturen erzielt, bei denen der Schwerpunkt durch verbesserte synthetische Methoden auf Graphen-Nanoribbons (NRs) lag. Trotz dieser Fortschritte bleibt die Kontrolle über die Stereochemie verdrehter NRs eine Herausforderung. Diese Dissertation stellt einen strategischen Ansatz vor, um absolute Kontrolle über die einhändig-helikale Konformation in einem cove-edged NR zu erreichen. Dabei werden enantiomerenreine [n]Helicene als molekulare Werkzeuge verwendet, um die Gesamtkonformation des NR präzise zu steuern. Enantiomerenreine [7]Helicene wurden mittels einer stereospezifischen und ortsselektiven Palladium(II)-katalysierten annulativen π-Erweiterungsreaktion (APEX) an die terminalen K-Regionen eines konjugierten Pyren-NR gebunden. Dies führte zu einem helikal-verdrehten NR mit einer End-zu-End-Windung von 171°, der zweithöchsten bisher in der Literatur für Twistacene berichteten Windung. Die helikale End-zu-End-Windung nimmt mit jeder Erweiterung um einen Benzolring zum zentralen Acenekern zu, was darauf hindeutet, dass die durch die terminalen [7]Helicene induzierte zusätzliche Spannung ein solch hohes Maß an Windung aufrechterhält. Quantenchemischen Berechnungen wurden durchgeführt, um den Einfluss der Verdrehung auf die konformationelle Population zu untersuchen. Bei Raumtemperatur nimmt das zentrale Rückgrat des Nanoribbons die entgegengesetzte Helizität zu der der angefügten [7]Helicene an, was etwa 99 % der molekularen Population ausmacht. Beispielsweise erzeugen (P)-[7]Helicene ein linkshändig-helikales Nanoribbon, während (M)-[7]Helicene ein rechtshändig-helikales Nanoribbon erzeugen. In Gegenwart von Helicenen entgegengesetzter Chiralität nimmt das Nanoribbon eine waggling-Konformation an. Die helikal-verdrehten Nanoribbons sbesitzen eine robuste Konformation, da chiroptische Messungen bei variablen Temperaturen keine Veränderung in den CD- und CPL-Spektren zeigten. Der vorgeschlagene Ansatz, der die Erweiterung durch [n]Helicen-Einheiten mithilfe der APEX-Reaktion umfasst, scheint vielversprechend für die Vereinfachung der Synthese verschiedener cove-edged NR-Varianten mit gewünschten Konformationen. Neben einhändig helikal-verdrehten Nanoribbons wurden die symmetriebasierten funktionellen Eigenschaften von C2- und C1-symmetrischen Pyren-gebundenen Einzel- und Doppel-[n]Helicenverbindungen untersucht. Aufgrund ihrer höheren strukturellen Rigidität zeigten die C1-symmetrischen heptagonalen Ringverbindungen außergewöhnliche hohe Konfigurationsstabilität sowie bemerkenswerte chiroptische Eigenschaften im Vergleich zu ihren C2-symmetrischen sowie reinen Helicen-Kongeneren. KW - Helicene KW - Pyren KW - Nanoribbon KW - Chirality KW - Acenes KW - Pyrene Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-360164 ER - TY - JOUR A1 - Kraus, Michael A1 - Grimm, Clemens A1 - Seibel, Jürgen T1 - Reversibility of a Point Mutation Induced Domain Shift: Expanding the Conformational Space of a Sucrose Phosphorylase JF - Scientific Reports N2 - 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. KW - biocatalysis KW - X-ray crystallography Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224845 VL - 8 ER - TY - THES A1 - Roger, Chantal T1 - Photophysics and Spin Chemistry of Triptycene Bridge Donor-Acceptor-Triads T1 - Photophysik und Spinchemie von Triptycen Brücken Donor-Akzeptor Triaden N2 - The goal of this thesis was to investigate the influence of rotational restriction between individual parts and of the varying electron density in the bridging unit of D B A systems on the exchange interaction 2J, and thus the electronic coupling between a donor state and an acceptor state. A better understanding of how to influence the underlaying spin dynamics in such donor acceptor systems can open up the door to new technologies, such as modern molecular electronics or optoelectronic devices. Therefore, three series of molecules consisting of a TAA electron donor, a TTC or ATC bridging unit and a PDI electron acceptor were studied. To investigate the influence of rotational restriction on 2J and the electronic coupling, a series of four rotationally hindered triads (chapter 6) was synthesised. The dihedral angle between the TAA and the TTC as well as between the TTC and the PDI was restricted by ortho methyl groups at the phenylene linkers of the connecting ends to the TTC bridge, producing a twist around the linking single bond which minimises the π overlap. The triads exhibit varying numbers of ortho methyl groups and therefore different degrees of rotational restriction. In order to shine light on the influence of varying electron density on 2J and the electronic coupling, a series of four substituted triptycene triads (chapter 7) was synthesised. The electron density in the TTC bridging unit was varied by electron donating and electron withdrawing groups in 12,13 position of the TTC bridging unit and thus varying its HOMO/LUMO energy. The last series of two anthracene bridge triads (chapter 8) connected both approaches by restricting the rotation with ortho methyl groups and simultaneously by varying the bridge energies. In order to obtain the electronic properties, steady state absorption and emission spectra of all triads were investigated (chapter 4). Here, all triads show spectral features associated with the separate absorption bands of TAA and the PDI moiety. The reduced QYs, compared to the unsubstituted PDI acceptor, indicate a non radiative quenching mechanism in all triads. The CV data (chapter 5) were used to calculate the energies of possible CSSs and those results were used to assign the CR dynamics into the different Marcus regions. fs TA measurements reveal that all triads form a CSS upon excitation of the PDI moiety. The lifetimes of the involved states and the rate constants were determined by global exponential fits and global target analysis. The CR dynamics upon depopulation of the CSSs were investigated using external magnetic field dependent ns TA spectroscopy. The ns TA maps show that all triads recombine via CRT pathway populating the local 3PDI state in toluene and provided the respective lifetimes. The approximate QYs of triplet formation were determined using actinometry. The magnetic field dependent ns TA data reveal the exchange interaction 2J between singlet and triplet CSS for each triad. Those magnetic field dependent ns TA data in toluene were furthermore treated using a quantum mechanical simulation (done by U.E. Steiner) to extract the rate constants kT and kS for CRT and CRS, respectively. However, the error margins of kS were rather wide. Finally, the electronic couplings between the donor and the acceptor states were obtained by combining the aforementioned experimental results of the rate constants and applying the Bixon Jortner theoretical description of diabatic ET and Andersons perturbative theory of the exchange coupling. Therefore, the experimentally determined values of 2J and the calculated values of kCS and kT were used. The rate constant kS was calculated based on the electronic coupling V1CSS 1S0. The rotationally hindered triads (chapter 6) show a strong influence of the degree of rotational restriction on the lifetimes and rate constants of the CS processes. The rate constants of CS are increasing with increasing rotational freedom. The magnetic field dependent decay data show that the exchange interactions increase with increasing rotational freedom. Based on the CR dynamics, the calculated electronic couplings of the ET processes reflect the same trend along the series. Here, only singlet couplings turned out to be strongly influenced while the triplet couplings are not. Therefore, this series shows that the ET dynamics of donor acceptor systems can strongly be influenced by restricting the rotational freedom. In the substituted triptycene triads (chapter 7), decreasing electron density in the bridging unit causes a decrease of the CS rate constants. The magnetic field dependent decay data show that with decreasing electron density in the bridge the exchange interaction decreases. The CR dynamics-based rate constants and the electronic couplings follow the same trend as the exchange interaction. This series shows that varying the HOMO/LUMO levels of the connecting bridge between donor and acceptor strongly influences the ET processes. In the anthracene bridge triads (chapter 8), the CS process is slow in both triads. The CR was fast in the anthracene triad and is slowed down in the methoxy substituted anthracene bridge triad. The increase of the exchange interaction with increasing electron density in the bridge was more pronounced than in the substituted triptycene triads. Thus, the variation of electron density in the bridge strongly influences the ET processes even though the rotation is restricted. In this thesis, it was shown that the influence of the rotational hindrance as well as the electron density in a connecting bridge have strong influence on all ET processes and the electronic coupling in donor acceptor systems. These approaches can therefore be used to modify magnetic properties of new materials. N2 - Das Ziel dieser Arbeit war es, den Einfluss von Rotationshinderung zwischen einzelnen Bausteinen und Variation der Elektronendichte in der Brückeneinheit eines Donor Brücke Akzeptor Systems auf die Austauschwechselwirkung 2J und somit die elektronische Kopplung zwischen dem Donor- und dem Akzeptor-Zustand zu untersuchen. Ein besseres Verständnis der zugrundeliegenden Spindynamiken in solchen Donor Akzeptor Systemen - und wie diese beeinflusst werden können - kann einen Zugang zu neuen Technologien wie molekularer Elektronik oder optoelektronischen Geräten ermöglichen. Im Zuge dessen wurden drei Molekülreihen, bestehend aus einem TAA Elektronendonor, einer TTC oder ATC Brücke und einem PDI Elektronenakzeptor, untersucht. Der Einfluss von eingeschränkter Rotation zwischen den einzelnen Bausteinen auf die Austauschwechselwirkung und die elektronische Kopplung wurde anhand einer Reihe von rotationsgehinderten Triaden (Kapitel 6) untersucht. Der Winkel zwischen der TAA und der TTC Einheit sowie zwischen der TTC und der PDI Einheit wurde durch ortho ständige Methylgruppen eingeschränkt. Dies führt zu einer Verdrillung um die verbrückende Einfachbindung. Um unterschiedliche Grade der Rotationshinderung zu erzielen, wurden die Triaden mit einer unterschiedlichen Anzahl von ortho Methylgruppen substituiert. Des Weiteren wurde eine Reihe, bestehend aus vier Triptycen substituierten Triaden (Kapitel 7), synthetisiert, um den Einfluss variierender Elektronendichte auf 2J und die elektronische Kopplung zu untersuchen. Die Elektronendichte in der TTC-Brückeneinheit wurde durch elektronenschiebende und elektronenziehende Gruppen in 12,13-Position an der TTC-Brückeneinheit variiert, was eine Änderung der HOMO/LUMO-Energien der Brücke zur Folge hat. Die letzte Reihe besteht aus zwei Anthracen verbrückten Triaden (Kapitel 8) und stellt die Kombination beider Ansätze dar. Um dies zu erzielen wurde die Rotation durch ortho-Methylgruppen vollständig unterdrückt und gleichzeitig die Brückenenergie verändert. Um die elektronischen Eigenschaften der Triaden zu untersuchen, wurden zunächst die stationären Absorptions und Emissionseigenschaften betrachtet (Kapitel 4). Die Absorptionsbanden können in allen Triaden der TAA sowie der PDI Einheit zugeordnet werden. Die Fluoreszenz Quantenausbeuten weisen, verglichen mit dem reinen PDI Akzeptor, deutlich geringere Werte auf. Dies deutet auf einen alternativen, nicht strahlenden Desaktivierungspfad hin. Mit Hilfe der CV Daten (Kapitel 5) wurde die Energie des ladungsgetrennten Zustandes für jede Triade berechnet und die Ladungsrekombinationspfade in die jeweiligen Marcus Regionen eingeordnet. fs transiente Absorptionsmessungen zeigen, dass alle Triaden einen ladungsgetrennten Zustand ausbilden. Die Lebenszeiten der beteiligten Zustände wurden mit Hilfe eines globalen exponentiellen Fits und die Ratenkonstanten mit Hilfe einer globalen Targetanalyse bestimmt. Die Ladungsrekombinationsdynamiken wurden mit Hilfe magnetfeldabhängiger ns transienter Absorptionsmessungen betrachtet. Die ns transienten Karten zeigen, dass alle Triaden in Toluol über den Triplett Rekombinationspfad in den lokalen Triplettzustand des PDI rekombinieren. Des Weiteren lieferten diese Messungen die Lebenszeiten des ladungsgetrennten Zustandes. Die Quantenausbeuten der Bildung des Triplettzustandes wurden mittels Actinometrie abgeschätzt. Mit Hilfe der magnetfeldabhängigen ns transienten Messungen konnte die Austauschwechselwirkung zwischen dem singulett und dem triplett ladungsgetrennten Zustand für jede Triade bestimmt werden. Um die Ratenkonstanten kT and kS der Triplett und Singulett Rekombination zu erhalten, wurden die Daten der magnetfeldabhängigen ns transienten Messungen mittels einer quantendynamischen Simulation untersucht (durchgeführt von U. E. Steiner, Universität Konstanz). Hierbei waren die Fehlergrenzen für kS jedoch sehr groß. Die elektronischen Kopplungen wurden mit Hilfe der Bixon Jortner Theorie des diabatischen elektronen Transfers und Andersons störungstheoritischem Ansatz zur Beschreibung der Austauschwechselwirkung aus den experimentellen Daten sowie den Ratenkonstanten berechnet. Hierfür wurden die die experimentell bestimmten 2J Werte sowie die berechneten Werte von kCS und kT verwendet. Um ein umfassendes Bild zu erhalten wurden die Ratenkonstanten kS aus den elektronischen Kopplungen V1CSS 1S0 berechnet. Die rotationsgehinderten Triaden (Kapitel 6) weisen eine starke Abhängigkeit der Ratenkonstanten des Ladungstrennungsprozesses vom Grad der Rotationseinschränkung auf. Hierbei steigen die Werte der Ratenkonstanten mit zunehmender Rotationsfreiheit. Der selbe Trend kann in der Austauschwechselwirkung bei Betrachtung der magnetfeldabhängigen Abklingkurven beobachtet werden. Des Weiteren zeigen die berechneten elektronischen Kopplungen ebenfalls eine Zunahme bei gesteigerter Rotationsfreiheit. Hierbei war zu beobachten, dass nur die Singulett Kopplungen von der Rotation beeinflusst wurden, Triplett Kopplungen jedoch nahezu unverändert blieben. Mit Hilfe dieser Reihe wurde gezeigt, dass Elektrontransferdynamiken durch Rotationseinschränkung beeinflusst werden können. In der Reihe der substituierten Triptycen Triaden (Kapitel 7) führt eine Abnahme der Elektronendichte in der Brücke zu einer Verringerung der Ratenkonstanten des Ladungstrennungsprozesses. Die Daten der magnetfeldabhängigen Abklingkurven zeigen, dass die Austauschwechselwirkung ebenfalls mit verringerter Elektronendichte in der Brücke abnimmt. Die berechneten elektronischen Kopplungen folgen dem Trend der Austauschwechselwirkung. Anhand dieser Reihe konnte gezeigt werden, dass Elektronentransferprozesse durch Veränderung der Brückenenergien beeinflusst werden können. In den Anthracen Brücken Triaden (Kapitel 8) ist die Ladungstrennung für beide Triaden langsam. Die Ladungsrekombination wird durch den elektronenschiebenden Effekt der Methoxygruppen, verlangsamt. Die Austauschwechselwirkung nimmt mit steigender Elektronendichte in der Brücke zu, wobei dieser Effekt stärker ausgeprägt ist als in den Triptycen substituierten Triaden. Die Variation der Elektronendichte hat somit, trotz vollständig gehinderter Rotation, einen starken Einfluss auf die Elektronentransferdynamiken. In dieser Arbeit konnte gezeigt werden, dass gehinderte Rotation und variierende Elektronendichte in einer Brückeneinheit einen starken Einfluss auf die Elektronentransferdynamiken und die elektronischen Kopplungen in Donor Akzeptor-Systemen haben. Diese Ansätze können somit dazu verwendet werden die magnetischen Eigenschaften von neuen Materialien zu verändern. KW - spin chemistry KW - Spinchemie KW - donor-acceptor triads KW - Donor-Akzeptor Triaden KW - Rotation KW - photophysics KW - electron transfer KW - rotation KW - electron density Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-363031 ER - TY - JOUR A1 - Gole, Bappaditya A1 - Stepanenko, Vladimir A1 - Rager, Sabrina A1 - Grüne, Matthias A1 - Medina, Dana D. A1 - Bein, Thomas A1 - Würthner, Frank A1 - Beuerle, Florian T1 - Microtubular Self-Assembly of Covalent Organic Frameworks JF - Angewandte Chemie International Edition N2 - Despite significant progress in the synthesis of covalent organic frameworks (COFs), reports on the precise construction of template-free nano- and microstructures of such materials have been rare. In the quest for dye-containing porous materials, a novel conjugated framework DPP-TAPP-COF with an enhanced absorption capability up to λ=800 nm has been synthesized by utilizing reversible imine condensations between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) and a diketopyrrolopyrrole (DPP) dialdehyde derivative. Surprisingly, the obtained COF exhibited spontaneous aggregation into hollow microtubular assemblies with outer and inner tube diameters of around 300 and 90 nm, respectively. A detailed mechanistic investigation revealed the time-dependent transformation of initial sheet-like agglomerates into the tubular microstructures. KW - covalent organic frameworks KW - diketopyrrolopyrroles KW - imines KW - microtubes KW - porphyrins Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227373 VL - 57 ER - TY - JOUR A1 - Bäumer, Nils A1 - Kartha, Kalathil K. A1 - Kumar Allampally, Naveen A1 - Yagai, Shiki A1 - Albuquerque, Rodrigo Q. A1 - Fernández, Gustavo T1 - Exploiting Coordination Isomerism for Controlled Self-Assembly JF - Angewandte Chemie International Edition N2 - We exploited the inherent geometrical isomerism of a PtII complex as a new tool to control supramolecular assembly processes. UV irradiation and careful selection of solvent, temperature, and concentration leads to tunable coordination isomerism, which in turn allows fully reversible switching between two distinct aggregate species (1D fibers↔2D lamellae) with different photoresponsive behavior. Our findings not only broaden the scope of coordination isomerism, but also open up exciting possibilities for the development of novel stimuli-responsive nanomaterials. KW - coordination isomerism KW - photoresponsive behavior KW - self-assembly KW - supramolecular polymers KW - p-conjugated systems Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-221362 VL - 58 ER - TY - JOUR A1 - Sol, Jeroen A. H. P. A1 - Dehm, Volker A1 - Hecht, Reinhard A1 - Würthner, Frank A1 - Schenning, Albertus P. H. J. A1 - Debije, Michael G. T1 - Temperature-Responsive Luminescent Solar Concentrators: Tuning Energy Transfer in a Liquid Crystalline Matrix JF - Angewandte Chemie International Edition N2 - Temperature-responsive luminescent solar concentrators (LSCs) have been fabricated in which the Förster resonance energy transfer (FRET) between a donor–acceptor pair in a liquid crystalline solvent can be tuned. At room temperatures, the perylene bisimide (PBI) acceptor is aggregated and FRET is inactive; while after heating to a temperature above the isotropic phase of the liquid crystal solvent, the acceptor PBI completely dissolves and FRET is activated. This unusual temperature control over FRET was used to design a color-tunable LSC. The device has been shown to be highly stable towards consecutive heating and cooling cycles, making it an appealing device for harvesting otherwise unused solar energy. KW - energy transfer KW - fluorescence KW - liquid crystals KW - luminescent solar concentrators KW - perylene dyes Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238778 VL - 57 ER - TY - JOUR A1 - Garain, Swadhin A1 - Shoyama, Kazutaka A1 - Ginder, Lea-Marleen A1 - Sárosi, Menyhárt A1 - Würthner, Frank T1 - The delayed box: biphenyl bisimide cyclophane, a supramolecular nano-environment for the efficient generation of delayed fluorescence JF - Journal of the American Chemical Society N2 - Activating delayed fluorescence emission in a dilute solution via a non-covalent approach is a formidable challenge. In this report, we propose a strategy for efficient delayed fluorescence generation in dilute solution using a non-covalent approach via supramolecularly engineered cyclophane-based nanoenvironments that provide sufficient binding strength to π-conjugated guests and that can stabilize triplet excitons by reducing vibrational dissipation and lowering the singlet–triplet energy gap for efficient delayed fluorescence emission. Toward this goal, a novel biphenyl bisimide-derived cyclophane is introduced as an electron-deficient and efficient triplet-generating host. Upon encapsulation of various carbazole-derived guests inside the nanocavity of this cyclophane, emissive charge transfer (CT) states close to the triplet energy level of the biphenyl bisimide are generated. The experimental results of host–guest studies manifest high association constants up to 10\(^4\) M\(^{–1}\) as the prerequisite for inclusion complex formation, the generation of emissive CT states, and triplet-state stabilization in a diluted solution state. By means of different carbazole guest molecules, we could realize tunable delayed fluorescence emission in this carbazole-encapsulated biphenyl bisimide cyclophane in methylcyclohexane/carbon tetrachloride solutions with a quantum yield (QY) of up to 15.6%. Crystal structure analyses and solid-state photophysical studies validate the conclusions from our solution studies and provide insights into the delayed fluorescence emission mechanism. KW - aromatic compounds KW - complexation KW - encapsulation KW - fluorescence KW - hydrocarbons Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-370385 SN - 0002-7863 VL - 146 IS - 31 ER -