TY - THES A1 - Wehner, Marius T1 - Supramolecular Polymorphism in Homo- and Heterochiral Supramolecular Polymerizations T1 - Supramolekularer Polymorphismus in homo- und heterochiralen supramolekularen Polymerisationen N2 - The aim of the first part of this thesis was to investigate (R,R)-PBI as a model system for polymorphism at its origin by a supramolecular approach. The pathway complexity of (R,R)-PBI was fine-tuned by experimental parameters such as solvent, temperature and concentration to make several supramolecular polymorphs accessible. Mechanistic and quantum chemical studies on the kinetics and thermodynamics of the supramolecular polymerization of (R,R)-PBI were conducted to shed light on the initial stages of polymorphism. The second part of this work deals with mechanistic investigations on the supramolecular polymerization of the racemic mixture of (R,R)- and (S,S)-PBI with regard to homochiral and heterochiral aggregation leading to conglomerates and a racemic supramolecular polymer, respectively. N2 - Das Ziel des ersten Teils der Dissertation war es, anhand des Modellsystems (R,R)-PBI Polymorphismus mit Hilfe eines supramolekularen Ansatzes an dessen Ursprung zu untersuchen. Durch die Wahl geeigneter experimenteller Parameter wie Lösungsmittel, Temperatur und Konzentration wurden die komplexen Polymerisationspfade von (R,R)-PBI gezielt beeinflusst und verschiedene supramolekulare Polymorphe zugänglich gemacht. Mechanistische und quantenchemische Untersuchungen der Kinetik und Thermodynamik der supramolekularen Polymerisation von (R,R)-PBI wurden durchgeführt, um die Anfangsphase des Polymorphismus zu beleuchten. Der zweite Teil der vorliegenden Arbeit befasst sich mit mechanistischen Untersuchungen der supramolekularen Polymerisation der racemischen Mischung aus (R,R)- und (S,S)-PBI im Hinblick auf homo- und heterochirale Aggregation, welche zu Konglomeraten beziehungsweise einem racemischen supramolekularen Polymer führte. KW - Supramolekulare Chemie KW - Polymorphismus KW - Konglomerat KW - Aggregat KW - Organische Chemie KW - Aggregation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-211519 ER - TY - JOUR A1 - Wehner, Marius A1 - Röhr, Merle Insa Silja A1 - Stepanenko, Vladimir A1 - Würthner, Frank T1 - Control of self-assembly pathways toward conglomerate and racemic supramolecular polymers JF - Nature Communications N2 - Homo- and heterochiral aggregation during crystallization of organic molecules has significance both for fundamental questions related to the origin of life as well as for the separation of homochiral compounds from their racemates in industrial processes. Herein, we analyse these phenomena at the lowest level of hierarchy - that is the self-assembly of a racemic mixture of (R,R)- and (S,S)-PBI into 1D supramolecular polymers. By a combination of UV/vis and NMR spectroscopy as well as atomic force microscopy, we demonstrate that homochiral aggregation of the racemic mixture leads to the formation of two types of supramolecular conglomerates under kinetic control, while under thermodynamic control heterochiral aggregation is preferred, affording a racemic supramolecular polymer. FT-IR spectroscopy and quantum-chemical calculations reveal unique packing arrangements and hydrogen-bonding patterns within these supramolecular polymers. Time-, concentration- and temperature-dependent UV/vis experiments provide further insights into the kinetic and thermodynamic control of the conglomerate and racemic supramolecular polymer formation. Homo- and heterochiral aggregation is a process of interest to prebiotic and chiral separation chemistry. Here, the authors analyze the self-assembly of a racemic mixture into 1D supramolecular polymers and find homochiral aggregation into conglomerates under kinetic control, while under thermodynamic control a racemic polymer is formed. KW - perylene bismide dye KW - nucleation-elongation KW - PI stacking KW - polymerization KW - complexity KW - mechanism KW - crystals KW - kinetics KW - growth Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230580 VL - 11 ER - TY - JOUR A1 - Farmer, Adam D. A1 - Strzelczyk, Adam A1 - Finisguerra, Alessandra A1 - Gourine, Alexander V. A1 - Gharabaghi, Alireza A1 - Hasan, Alkomiet A1 - Burger, Andreas M. A1 - Jaramillo, Andrés M. A1 - Mertens, Ann A1 - Majid, Arshad A1 - Verkuil, Bart A1 - Badran, Bashar W. A1 - Ventura-Bort, Carlos A1 - Gaul, Charly A1 - Beste, Christian A1 - Warren, Christopher M. A1 - Quintana, Daniel S. A1 - Hämmerer, Dorothea A1 - Freri, Elena A1 - Frangos, Eleni A1 - Tobaldini, Eleonora A1 - Kaniusas, Eugenijus A1 - Rosenow, Felix A1 - Capone, Fioravante A1 - Panetsos, Fivos A1 - Ackland, Gareth L. A1 - Kaithwas, Gaurav A1 - O'Leary, Georgia H. A1 - Genheimer, Hannah A1 - Jacobs, Heidi I. L. A1 - Van Diest, Ilse A1 - Schoenen, Jean A1 - Redgrave, Jessica A1 - Fang, Jiliang A1 - Deuchars, Jim A1 - Széles, Jozsef C. A1 - Thayer, Julian F. A1 - More, Kaushik A1 - Vonck, Kristl A1 - Steenbergen, Laura A1 - Vianna, Lauro C. A1 - McTeague, Lisa M. A1 - Ludwig, Mareike A1 - Veldhuizen, Maria G. A1 - De Couck, Marijke A1 - Casazza, Marina A1 - Keute, Marius A1 - Bikson, Marom A1 - Andreatta, Marta A1 - D'Agostini, Martina A1 - Weymar, Mathias A1 - Betts, Matthew A1 - Prigge, Matthias A1 - Kaess, Michael A1 - Roden, Michael A1 - Thai, Michelle A1 - Schuster, Nathaniel M. A1 - Montano, Nicola A1 - Hansen, Niels A1 - Kroemer, Nils B. A1 - Rong, Peijing A1 - Fischer, Rico A1 - Howland, Robert H. A1 - Sclocco, Roberta A1 - Sellaro, Roberta A1 - Garcia, Ronald G. A1 - Bauer, Sebastian A1 - Gancheva, Sofiya A1 - Stavrakis, Stavros A1 - Kampusch, Stefan A1 - Deuchars, Susan A. A1 - Wehner, Sven A1 - Laborde, Sylvain A1 - Usichenko, Taras A1 - Polak, Thomas A1 - Zaehle, Tino A1 - Borges, Uirassu A1 - Teckentrup, Vanessa A1 - Jandackova, Vera K. A1 - Napadow, Vitaly A1 - Koenig, Julian T1 - International Consensus Based Review and Recommendations for Minimum Reporting Standards in Research on Transcutaneous Vagus Nerve Stimulation (Version 2020) JF - Frontiers in Human Neuroscience N2 - Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice. KW - transcutaneous vagus nerve stimulation KW - minimum reporting standards KW - guidelines & recommendations KW - transcutaneous auricular vagus nerve stimulation KW - transcutaneous cervical vagus nerve stimulation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234346 SN - 1662-5161 VL - 14 ER -