@article{GrandeSoberatsHerbstetal.2018,
  author    = {Grande, Vincenzo and Soberats, Bartolome and Herbst, Stefanie and Stepanenko, Vladimir and W{\"u}rthner, Frank},
  title     = {Hydrogen-bonded perylene bisimide J-aggregate aqua material},
  volume    = {9},
  issn      = {2041-6539},
  doi       = {10.1039/C8SC02409J},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204715},
  pages     = {6904-6911},
  year      = {2018},
  abstract  = {A new twelvefold methoxy-triethyleneglycol-jacketed tetraphenoxy-perylene bisimide (MEG-PBI) amphiphile was synthesized that self-assembles into two types of supramolecular aggregates in water: red-coloured aggregates of low order and with weak exciton coupling among the PBIs and blue-coloured strongly coupled J-aggregates consisting of a highly ordered hydrogen-bonded triple helix of PBIs. At room temperature this PBI is miscible with water at any proportions which enables the development of robust dye aggregates in solution, in hydrogel states and in lyotropic liquid crystalline states. In the presence of 60-95 wt\% water, self-standing coloured hydrogels exhibit colour changes from red to blue accompanied by a fluorescence light-up in the far-red region upon heating in the range of 30-50 °C. This phenomenon is triggered by an entropically driven temperature-induced hydrogen-bond-directed slipped stacking arrangement of the MEG-PBI chromophores within structurally well-defined J-aggregates. This versatile aqua material is the first example of a stable PBI J-aggregate in water. We anticipate that this study will open a new avenue for the development of biocompatible functional materials based on self-assembled dyes and inspire the construction of other hydrogen-bonded supramolecular materials in the highly competitive solvent water.},
  language  = {en}
}
@article{RennerStolteWuerthner2020,
  author    = {Renner, Rebecca and Stolte, Matthias and W{\"u}rthner, Frank},
  title     = {Self-Assembly of bowl-shaped naphthalimide-annulated corannulene},
  series = {ChemistryOpen},
  volume    = {9},
  journal   = {ChemistryOpen},
  number    = {1},
  doi       = {10.1002/open.201900291},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204396},
  pages     = {32-39},
  year      = {2020},
  abstract  = {The self-assembly of a bowl-shaped naphthalimide-annulated corannulene of high solubility has been studied in a variety of solvents by NMR and UV/Vis spectroscopy. Evaluation by the anti-cooperative K\(_2\)-K model revealed the formation of supramolecular dimers of outstanding thermodynamic stability. Further structural proof for the almost exclusive formation of dimers over extended aggregates is demonstrated by atomic force microscopy (AFM) and diffusion ordered spectroscopy (DOSY) measurements as well as by theoretical calculations. Thus, herein we present the first report of a supramolecular dimer of an annulated corannulene derivative in solution and discuss its extraordinarily high thermodynamic stability with association constants up to > 10\(^6\)M\(^-\) \(^1\) in methylcyclohexane, which is comparable to the association constants given for planar phthalocyanine and perylene bisimide dyes.},
  language  = {en}
}
@article{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{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{FayezFeineisAkeAssietal.2019,
  author    = {Fayez, Shaimaa and Feineis, Doris and Ak{\´e} Assi, Laurent and Seo, Ean-Jeong and Efferth, Thomas and Bringmann, Gerhard},
  title     = {Ancistrobreveines A-D and related dehydrogenated naphthylisoquinoline alkaloids with antiproliferative activities against leukemia cells, from the West African liana Ancistrocladus abbreviatus},
  series = {RSC Advances},
  volume    = {9},
  journal   = {RSC Advances},
  number    = {28},
  doi       = {10.1039/C9RA03105G},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201686},
  pages     = {15738-15748},
  year      = {2019},
  abstract  = {A unique series of six biaryl natural products displaying four different coupling types (5,10 , 7,10 , 7,80 , and 5,80) were isolated from the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Although at first sight structurally diverse, these secondary metabolites all have in common that they belong to the rare group of naphthylisoquinoline alkaloids with a fully dehydrogenated isoquinoline portion. Among the African Ancistrocladus species, A. abbreviatus is so far only the second one that was found to produce compounds with such a molecular entity. Here, we report on four new representatives, named ancistrobreveines A-D (12-14, and 6). They were identified along with the two known alkaloids 6-O-methylhamateine (4) and entdioncophylleine A (10). The two latter naphthylisoquinolines had so far only been detected in Ancistrocladus species from Southeast Asia. All of these fully dehydrogenated alkaloids have in common being optically active despite the absence of stereogenic centers, due to the presence of the rotationally hindered biaryl axis as the only element of chirality. Except for ent-dioncophylleine A (10), which lacks an oxygen function at C-6, the ancistrobreveines A-D (12-14, and 6) and 6-O-methylhamateine (4) are 6-oxygenated alkaloids, and are, thus, typical 'Ancistrocladaceae-type' compounds. Ancistrobreveine C (14), is the first - and so far only - example of a 7,80-linked fully dehydrogenated naphthylisoquinoline discovered in nature that is configurationally stable at the biaryl axis. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR) and chiroptical (electronic circular dichroism) methods. Ancistrobreveine C (14) and 6-O-methylhamateine (4) exhibited strong antiproliferative activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrugresistant subline, CEM/ADR5000.},
  language  = {en}
}
@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{TshitengeTshitengeBruhnFeineisetal.2019,
  author    = {Tshitenge Tshitenge, Dieudonn{\´e} and Bruhn, Torsten and Feineis, Doris and Mudogo, Virima and Kaiser, Marcel and Brun, Reto and Bringmann, Gerhard},
  title     = {An unusually broad series of seven cyclombandakamines, bridged dimeric naphthylisoquinoline alkaloids from the Congolese liana Ancistrocladus ealaensis},
  series = {Scientific Reports},
  volume    = {9},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-019-46336-z.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200759},
  pages     = {9812},
  year      = {2019},
  abstract  = {A series of seven unusual dimeric naphthylisoquinoline alkaloids was isolated from the leaves of the tropical liana Ancistrocladus ealaensis J. L{\´e}onard, named cyclombandakamine A (1), 1-epi-cyclombandakamine A (2), and cyclombandakamines A3-7 (3-7). These alkaloids have a chemically thrilling structural array consisting of a twisted dihydrofuran-cyclohexenone-isochromene system. The 1′″-epimer of 4, cyclombandakamine A1 (8), had previously been discovered in an unidentified Ancistrocladus species related to A. ealaensis. Both lianas produce the potential parent precursor, mbandakamine A (9), but only A. ealaensis synthesizes the corresponding cyclized form, along with a broad series of slightly modified analogs. The challenging isolation required, besides multi-dimensional chromatography, the use of a pentafluorophenyl stationary phase. Featuring up to six stereocenters and two types of chiral axes, their structures were elucidated by means of 1D and 2D NMR, HRESIMS, in combination with oxidative chemical degradation experiments as well as chiroptical (electronic circular dichroism spectroscopy) and quantum chemical calculations. Compared to the 'open-chain' parent compound 9, these dimers displayed rather moderate antiplasmodial activities.},
  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{SteinmetzgerBaeuerleinHoebartner2020,
  author    = {Steinmetzger, Christian and B{\"a}uerlein, Carmen and H{\"o}bartner, Claudia},
  title     = {Supramolecular fluorescence resonance energy transfer in nucleobase-modified fluorogenic RNA aptamers},
  series = {Angewandte Chemie, International Edition},
  volume    = {59},
  journal   = {Angewandte Chemie, International Edition},
  doi       = {10.1002/anie.201916707},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203084},
  pages     = {6760-6764},
  year      = {2020},
  abstract  = {RNA aptamers form compact tertiary structures and bind their ligands in specific binding sites. Fluorescence-based strategies reveal information on structure and dynamics of RNA aptamers. Here we report the incorporation of the universal emissive nucleobase analog 4-cyanoindole into the fluorogenic RNA aptamer Chili, and its application as a donor for supramolecular FRET to bound ligands DMHBI+ or DMHBO+. The photophysical properties of the new nucleobase-ligand-FRET pair revealed structural restraints for the overall RNA aptamer organization and identified nucleotide positions suitable for FRET-based readout of ligand binding. This strategy is generally suitable for binding site mapping and may also be applied for responsive aptamer devices.},
  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{HollmannWieseDennstaedtetal.2019,
  author    = {Hollmann, Claudia and Wiese, Teresa and Dennst{\"a}dt, Fabio and Fink, Julian and Schneider-Schaulies, J{\"u}rgen and Beyersdorf, Niklas},
  title     = {Translational approaches targeting ceramide generation from sphingomyelin in T cells to modulate immunity in humans},
  series = {Frontiers in Immunology},
  volume    = {10},
  journal   = {Frontiers in Immunology},
  number    = {2363},
  issn      = {1664-3224},
  doi       = {10.3389/fimmu.2019.02363},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-198806},
  year      = {2019},
  abstract  = {In T cells, as in all other cells of the body, sphingolipids form important structural components of membranes. Due to metabolic modifications, sphingolipids additionally play an active part in the signaling of cell surface receptors of T cells like the T cell receptor or the co-stimulatory molecule CD28. Moreover, the sphingolipid composition of their membranes crucially affects the integrity and function of subcellular compartments such as the lysosome. Previously, studying sphingolipid metabolism has been severely hampered by the limited number of analytical methods/model systems available. Besides well-established high resolution mass spectrometry new tools are now available like novel minimally modified sphingolipid subspecies for click chemistry as well as recently generated mouse mutants with deficiencies/overexpression of sphingolipid-modifying enzymes. Making use of these tools we and others discovered that the sphingolipid sphingomyelin is metabolized to ceramide to different degrees in distinct T cell subpopulations of mice and humans. This knowledge has already been translated into novel immunomodulatory approaches in mice and will in the future hopefully also be applicable to humans. In this paper we are, thus, summarizing the most recent findings on the impact of sphingolipid metabolism on T cell activation, differentiation, and effector functions. Moreover, we are discussing the therapeutic concepts arising from these insights and drugs or drug candidates which are already in clinical use or could be developed for clinical use in patients with diseases as distant as major depression and chronic viral infection.},
  language  = {en}
}
@phdthesis{Buschmann2019,
  author    = {Buschmann, Rachel Abigail},
  title     = {Synthesis of annulated pi-systems based on a tribenzotriquinacene core},
  doi       = {10.25972/OPUS-19349},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-193491},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {The aim of this work was the selective functionalisation of tribenzotriquinacene (TBTQ) in order to extend the aromatic system and tune the electronic properties. The synthesised molecules could be starting materials for a model system of a defective graphene fragment. The "triple cyclisation pathway" by Hopf et al. was adapted and fluorinated tribenzotriquinacenes were synthesised for the first time. Phenanthrene groups were also introduced in other model systems and the crystal structures of phenanthrene functionalised TBTQs were compared with the parent molecules. In addition, the arrangement of TBTQ and centro methyl functionalised TBTQ was investigated on a Ag(111) surface for the first time using scanning transmission microscopy (STM). Different arrangements were observed, depending on the coverage of the surface. The insights gained about the interaction between TBTQs as well as their synthesis provide a foundation for further work and potential applications as components in organic electronic devices.},
  subject      = {Triquinacenderivate},
  language  = {en}
}
@phdthesis{Wagner2019,
  author    = {Wagner, Wolfgang},
  title     = {Supramolecular Block Copolymers by Seeded Living Supramolecular Polymerization of Perylene Bisimides},
  doi       = {10.25972/OPUS-19300},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-193004},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {The research on supramolecular polymerization has undergone a rapid development in the last two decades, particularly since supramolecular polymers exhibit a broad variety of functionalities and applications in organic electronics, biological science or as functional materials (Chapter 2.1). Although former studies have focused on investigation of the thermodynamics of supramolecular polymerization (Chapter 2.2), the academic interest in the recent years shifted towards gaining insight into kinetically controlled self-assembly and pathway complexity to generate novel out-of-equilibrium architectures with interesting nanostructures and features (Chapter 2.3). Along this path, the concepts of seeded and living supramolecular polymerization were recently developed to enable the formation of supramolecular polymers with controlled length and low polydispersity under precise kinetic control (Chapter 2.4). Besides that, novel strategies were developed to achieve supramolecular copolymerization resulting in complex multicomponent nanostructures with different structural motives. The classification of these supramolecular copolymers on the basis of literature examples and an overview of previously reported principles to create such supramolecular architectures are provided in Chapter 2.5. The aim of the thesis was the non-covalent synthesis of highly desirable supramolecular block copolymers by the approach of living seeded supramolecular polymerization and to study the impact of the molecular shape of the monomeric building blocks on the supramolecular copolymerization. Based on the structure of the previously investigated PBI organogelator H-PBI a series of novel PBIs, bearing identical hydrogen-bonding amide side-groups in imide-position and various kind or number of substituents in bay-position, was synthesized and analyzed within this thesis. The new PBIs were successfully obtained in three steps starting from the respective bromo-substituted perylene-3,4:9,10-tetracarboxylic acid tetrabutylesters or from the N,N'-dicyclohexyl-1,7-dibromoperylene-3,4:9,10-tetracarboxylic acid bisimide. All target compounds were obtained in the final step by imidization reactions of the respective perylene tetracarboxylic acid bisanhydride precursors with N-(2-aminoethyl)-3,4,5-tris(dodecyloxy)-benzamide and were fully characterized by 1H and 13C NMR spectroscopy as well as high resolution mass spectrometry. The variation of bay-substituents strongly changes the optical properties of the monomeric PBIs which were investigated by UV/vis and fluorescence spectroscopy. The increase of the number of the methoxy-substituents provokes, for example, a red-shift of the absorption maxima concomitant with a decrease of extinction coefficients and leads to a drastic increase of the fluorescence quantum yields. Furthermore, the molecular geometry of the PBIs is also affected by variations of the bay-substituents. Thus, increasing the steric demand of the bay-substituents leads to an enlargement of the twist angles of the PBI cores as revealed by DFT calculations. Especially the 1,7-dimethoxy bay-substituted MeO-PBI proved to be very well-suited for the studies envisioned within this thesis. The self-assembly of this PBI derivative was analyzed in detail by UV/vis, fluorescence and FT-IR spectroscopy as well as atomic force microscopy (Chapter 3). These studies revealed that MeO-PBI forms in a solvent mixture of methylcyclohexane and toluene (2:1, v/v) kinetically trapped off-pathway H-aggregated nanoparticles upon fast cooling of a monomeric solution from 90 to 20 °C. However, upon slow cooling of the monomer solution fluorescent J-type nanofibers are formed by π π interactions and intermolecular hydrogen-bonding. The kinetically metastable off-pathway H-aggregates can be transformed into the thermodynamically more favored J-type aggregates by addition of seeds, which are produced by ultrasonication of the polymeric nanofibers. Interestingly, the living character of this seed-induced supramolecular polymerization process was proven by a newly designed multicycle polymerization experimental protocol. This living polymerization experiment clearly proves, that the polymerization can only occur at the "active" ends of the polymeric seed and that almost no recombination or chain termination processes are present. Hence, the approach of living supramolecular polymerization enables the formation of supramolecular polymers with controlled length and narrow polydispersity. In Chapter 4 the copolymerization of MeO-PBI with the structurally similar 1,7-dichloro (Cl-PBI) and 1,7-dimethylthio (MeS-PBI) bay-substituted PBIs is studied in detail. Both PBIs form analogous to MeO-PBI kinetically trapped off-pathway aggregates, which can be converted into the thermodynamically stable supramolecular polymers by seed-induced living supramolecular polymerization under precise kinetic control. However, the stability of the kinetically trapped aggregates of Cl-PBI and MeS-PBI is distinctly reduced compared to that of MeO-PBI, because the π-π-interactions of the kinetically metastable aggregates are hampered through the increased twisting of the PBI-cores of the former PBIs. UV/vis studies revealed that the two-component seeded copolymerization of the kinetically trapped state of MeO-PBI with seeds of Cl-PBI leads to the formation of unprecedented supramolecular block copolymers with A-B-A pattern by a living supramolecular polymerization process at the termini of the seeds. Remarkably, the resulting A-B-A block pattern of the obtained copolymers was clearly confirmed by atomic force microscopy studies as the respective blocks formed by the individual monomeric units could be distinguished by the pitches of the helical nanofibers. Moreover, detailed UV/vis and AFM studies have shown that by inverted two-component seed-induced polymerization, e.g., upon addition of seeds of MeO-PBI to the kinetically trapped aggregates of Cl-PBI, triblock supramolecular copolymers with B-A-B pattern can be generated. The switching of the block pattern could only be achieved because of the perfectly matching conditions for the copolymerization process and the tailored molecular geometry of the individual building blocks of both PBIs. These studies have demonstrated for the first time, that the block pattern of a supramolecular copolymer can be modulated by the experimental protocol through the approach of living supramolecular polymerization. Furthermore, by UV/vis analysis of the living copolymerization of MeO-PBI and MeS-PBI similar results were obtained showing also the formation of both A-B-A and B-A-B type supramolecular block copolymers. Although for these two PBIs the individual blocks could not be identified by AFM because the helical nanofibers of both PBIs exhibit identical helical pitches, these studies revealed for the first time that the approach of seeded living polymerization is not limited to a special pair of monomeric building blocks. In the last part of the thesis (Chapter 5) a systematic study on the two-component living copolymerization of PBIs with various sterical demanding bay-substituents is provided. Thus, a series of PBIs containing identical hydrogen-bonding amide groups in imide position but variable number (1-MeO-PBI, MeO-PBI, 1,6,7-MeO-PBI, 1,6,7,12-MeO-PBI) or size (EtO-PBI, iPrO-PBI) of alkoxy bay-substituents was investigated. The molecular geometry of the monomeric building blocks has a strong impact on the thermodynamically and even more pronounced on the kinetically controlled aggregation in solvent mixtures of MCH and Tol. While the mono- and dialkoxy-substituted PBIs form kinetically metastable species, the self-assembly of the tri- and tetramethoxy-substituted PBIs (1,6,7-MeO-PBI and 1,6,7,12-MeO-PBI) is completely thermodynamically controlled. The two 1,7-alkoxy substituted PBIs (EtO-PBI, iPrO-PBI) form very similar to MeO-PBI kinetically off-pathway H-aggregates and thermodynamically more favored J-type aggregates. However, the stability of the kinetically metastable state is drastically lower and the conversion into the thermodynamically favored state much faster than for MeO-PBI. In contrast, the monomethoxy-substituted PBI derivative (1-MeO-PBI) forms a kinetically trapped species by intramolecular hydrogen-bonding of the monomers, which can be transformed into the thermodynamically favored nanofibers by seeded polymerization. Importantly, the two-component seeded copolymerization of the kinetically trapped MeO PBI with seeds of other PBIs of the present series was studied by UV/vis and AFM revealing that the formation of supramolecular block copolymers is only possible for appropriate combinations of PBI building blocks. Thus, the seeded polymerization of the trapped state of the moderately core-twisted MeO-PBI with the, according to DFT-calculations, structurally similar PBIs (EtO-PBI and iPrO-PBI) leads to the formation of A-B-A block copolymers, like in the seeded copolymerization of MeO-PBItrapped with seeds of Cl-PBI and MeS-PBI already described in Chapter 4. However, by addition of seeds of the almost planar PBIs (H-PBI and 1-MeO-PBI) or seeds of the strongly core-twisted PBIs (1,6,7-MeO-PBI and 1,6,7,12-MeO-PBI) to the kinetically trapped state of MeO-PBI no block copolymers can be obtained. The mismatching geometry of these molecular building blocks strongly hampers both the intermolecular hydrogen-bonding and the π-π-interactions between the two different PBIs and consequently prevents the copolymerization process. Furthermore, the studies of the two-component seeded copolymerization of the kinetically trapped species of 1-MeO-PBI with seeds of the other PBIs also corroborated that a precise shape complementarity is crucial to generate supramolecular block copolymers. Thus, by addition of seeds of H-PBI to the kinetically trapped monomers of 1-MeO-PBI supramolecular block copolymers were generated. Both PBIs exhibit an almost planar PBI core according to DFT-calculations leading to strong non-covalent interactions between these PBIs. This perfectly matching geometry of both PBIs also enables the inverted seeded copolymerization of the kinetically trapped monomers of H-PBI with 1-MeO-PBIseed concomitant with a switching of the block pattern of the supramolecular copolymer from A-B-A to B-A-B type. In contrast, the seeding with the moderately twisted (MeO-PBI, EtO-PBI and iPrO-PBI) and the strongly twisted PBIs (1,6,7-MeO-PBI and 1,6,7,12 MeO-PBI) has no effect on the kinetically trapped state of 1-MeO-PBI, because the copolymerization of these PBIs is prevented by the mismatching geometry of the molecular building blocks. In conclusion, the supramolecular polymerization and two-component seeded copolymerization of a series of PBI monomers was investigated within this thesis. The studies revealed that the thermodynamically and kinetically controlled self-assembly can be strongly modified by subtle changes of the monomeric building blocks. Moreover, the results have shown that living supramolecular polymerization is an exceedingly powerful method to generate unprecedented supramolecular polymeric nanostructures with controlled block pattern and length distribution. The formation of supramolecular block copolymers can only be achieved under precise kinetic control of the polymerization process and is strongly governed by the shape complementarity already imparted in the individual components. Thus, these insightful studies might enable a more rational design of monomeric building blocks for the non-covalent synthesis of highly complex supramolecular architectures with interesting properties for possible future applications, e.g., as novel functional materials.},
  subject      = {Supramolekulare Chemie},
  language  = {en}
}
@article{SteinmetzgerBessiLenzetal.2019,
  author    = {Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and H{\"o}bartner, Claudia},
  title     = {Structure-fluorescence activation relationships of a large Stokes shift fluorogenic RNA aptamer},
  series = {Nucleic Acids Research},
  journal   = {Nucleic Acids Research},
  doi       = {10.1093/nar/gkz1084/5628921},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192340},
  pages     = {gkz1084},
  year      = {2019},
  abstract  = {The Chili RNA aptamer is a 52 nt long fluorogen-activating RNA aptamer (FLAP) that confers fluorescence to structurally diverse derivatives of fluorescent protein chromophores. A key feature of Chili is the formation of highly stable complexes with different ligands, which exhibit bright, highly Stokes-shifted fluorescence emission. In this work, we have analyzed the interactions between the Chili RNA and a family of conditionally fluorescent ligands using a variety of spectroscopic, calorimetric and biochemical techniques to reveal key structure - fluorescence activation relationships (SFARs). The ligands under investigation form two categories with emission maxima of ~540 nm or ~590 nm, respectively, and bind with affinities in the nanomolar to low-micromolar range. Isothermal titration calorimetry was used to elucidate the enthalpic and entropic contributions to binding affinity for a cationic ligand that is unique to the Chili aptamer. In addition to fluorescence activation, ligand binding was also observed by NMR spectroscopy, revealing characteristic signals for the formation of a G-quadruplex only upon ligand binding. These data shed light on the molecular features required and responsible for the large Stokes shift and the strong fluorescence enhancement of red and green emitting RNA-chromophore complexes.},
  language  = {en}
}
@phdthesis{MufusamaKoySita2019,
  author    = {Mufusama Koy Sita, Jean-Pierre},
  title     = {Quality Assessment of Antimalarial Medicines Sold in the Democratic Republic of the Congo and Phytochemical Investigations on a Congolese Ancistrocladus Liana},
  doi       = {10.25972/OPUS-19238},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192382},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Nowadays, the management of infectious diseases is especially threatened by the rapid emergence of drug resistance. It has been suggested that the medicine quality assurance combined with good medication adherence may help to reduce this impendence. Moreover, the search for new antimicrobial agents from medicinal plants is strongly encouraged for the exploration of alternatives to existing therapies. In this context, the present work focused on both the quality evaluation of commercialized antimalarial medicines from the Democratic Republic of the Congo and on the phytochemical investigations of a Congolese Ancistrocladus species.},
  subject      = {Antimalariamittel},
  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}
}
@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}
}
@phdthesis{Seaf2019,
  author    = {Seaf, Shaimaa Fayez Ali Mohammed},
  title     = {Isolation, structural elucidation, and biological evaluation of Naphthylisoquinoline alkaloids from two African Ancistrocladus species},
  doi       = {10.25972/OPUS-19158},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191588},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {The indepth metabolic profiling of the crude extracts of two African Ancistrocladus species viz. A. likoko from Central Africa and A. abbreviatus from West Africa, resulted in a total of 87 alkaloids among them 54 new ones. All of the compounds were intensely elucidated by 1D and 2D NMR, HRESIMS, as well as chemical and chiroptical techniques. Among the newly discovered compounds are quinoid naphthylisoquinolines with an ortho-diketone in the naphthalene portion, nor-naphthylisoquinoline alkaloid lacking the always present methyl group at C-1, seco-(ring cleaved) naphthylisoquinolines, and a newly discovered class of natural products called the naphthylisoindolinones. Some of the compounds displayed strong antitumoral activities against human pancreatic cancer cells and leukemia cells in-vitro.},
  subject      = {Naphthylisochinolinalkaloide},
  language  = {en}
}
@article{TshitengeFeineisMudogoetal.2017,
  author    = {Tshitenge, Dieudonn{\´e} Tshitenge and Feineis, Doris and Mudogo, Virima and Kaiser, Marcel and Brun, Reto and Bringmann, Gerhard},
  title     = {Antiplasmodial Ealapasamines A-C,'Mixed' Naphthylisoquinoline Dimers from the Central African Liana Ancistrocladus ealaensis},
  series = {Scientific Reports},
  volume    = {7},
  journal   = {Scientific Reports},
  number    = {5767},
  doi       = {10.1038/s41598-017-05719-w},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170645},
  year      = {2017},
  abstract  = {Three unusual heterodimeric naphthylisoquinoline alkaloids, named ealapasamines A-C (1-3), were isolated from the leaves of the tropical plant Ancistrocladus ealaensis J. L{\´e}onard. These 'mixed', constitutionally unsymmetric dimers are the first stereochemically fully assigned cross-coupling products of a 5,8′- and a 7,8′-coupled naphthylisoquinoline linked via C-6′ in both naphthalene portions. So far, only two other West and Central Ancistrocladus species were known to produce dimers with a central 6,6″-axis, yet, in contrast to the ealapasamines, usually consisting of two 5,8′-coupled monomers, like e.g., in michellamine B. The new dimers 1-3 contain six elements of chirality, four stereogenic centers and the two outer axes, while the central biaryl axis is configurationally unstable. The elucidation of the complete stereostructures of the ealapasamines was achieved by the interplay of spectroscopic methods including HRESIMS, 1D and 2D NMR (in particular ROESY measurements), in combination with chemical (oxidative degradation) and chiroptical (electronic circular dichroism) investigations. The ealapasamines A-C display high antiplasmodial activities with excellent half-maximum inhibition concentration values in the low nanomolar range.},
  language  = {en}
}
@phdthesis{HerbstgebHoehne2019,
  author    = {Herbst [geb. H{\"o}hne], Stefanie},
  title     = {Liquid Crystalline Perylene Bisimide Assemblies},
  doi       = {10.25972/OPUS-16485},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164857},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Thus, the main focus of this thesis was to generate and investigate new one-dimensional LC PBI J-aggregates of an entirely new PBI organization with the transition dipole moments of the chromophores arranged parallel to the columnar axis and in slipped pi-pi stacking fashion to form highly fluorescent J-aggregates. Towards this goal, the tetra-bay substituted PBI 4c bearing free NH functional groups at the imide positions and four dendrons with branched ethylhexyl alkoxy chains at the meta-position of the phenoxy spacer (Figure 8.1a) was synthesized and compared to a literature known reference PBI 1. The mesogenic dendrons ensure LC character of the dye, which was confirmed by POM, DSC and extensive X-ray analysis. Furthermore, the sterically demanding bay-substituents prevent the cofacial assembly of the chromophores and force the dyes into a slipped pi-stacked order with the main transition dipole moments of the dyes oriented parallel to the columnar axis. X-ray analysis revealed that PBI 4c assembles into columnar triple-stranded helices consisting of side-to-side stacked molecules, which organize into a Colh phase (Figure 8.1b). FT-IR experiments of a thin film and aggregates in MCH solution confirmed the formation of H-bonds between the imide moieties. Temperature-dependent investigations furthermore proved a reversible formation of H-bonds and polarized FT-IR experiments finally gave evidence for the direction of the H-bonds along the shearing respective the columnar axis (Figure 8.1c). This was additionally verified by polarized UV-Vis absorption studies of aligned thin films. The changes in the UV-Vis absorption spectra of concentration- and temperature-dependent experiments in MCH are in agreement with the formation of J-aggregates and could be fitted to a nucleation-elongation growth mechanism. Remarkably, fluorescence spectroscopy studies revealed highly emissive aggregates in solution. These various spectroscopic techniques proved the utilization of directional noncovalent forces like hydrogen-bonding and pi-pi interactions in a cooperative manner forcing the PBI molecules in an unprecedented organization of a slipped pi-stacked arrangement with the orientation of the molecular axis and the respective transition dipole moments parallel to the columns of the LC phase. By the group of Dietrich the formation of exciton-polaritons in imprinted LC pillar microcavities as consequent use of the LC 4c was reported for the first time.In the second part of this thesis the hierarchical organization of LC PBIs into defined single-, double-, triple- and quadruple-stranded J-aggregates within crystalline and columnar LC phases, partially arranged in helical supramolecular structures in dependence of the molecular design was demonstrated. This was achieved via the preparation of a library of twelve molecules PBI 3-6(a-c) (Figure 8.2a) that was synthesized by varying the substitution position of the dendrons at the phenoxy-spacer from ortho to meta or para and by introducing an additional methyl group in ortho-position. Also the length and shape of the alkoxy chains was changed. Consequently, the impact of the sterical demand of the bay substituents concerning their phase properties, molecular arrangement and exciton coupling was investigated. POM, DSC and X-ray studies revealed the formation of only crystalline phase for the ortho-substituted PBIs 3a-c, whereas the other derivatives generated SC or LC phases. The main focus was the series with the n-C12-alkoxy chains. For the corresponding PBIs 4-6b columnar LC phases were confirmed. Retrostructural analysis by modelling and simulations gave indications for a single stranded organization for PBI 3b, a double-stranded helix for PBI 6b, a triple-stranded helical arrangement for PBI 5b and a quadruple-stranded helix for PBI 4b (Figure 8.2b-d). For all four derivatives the same molecular orientation within the columns as for PBI 4c was proven by polarized FT-IR and UV-Vis absorption studies in aligned thin films. The organization in helices of different number of strands in the Cr and LC phases of PBI 3b, 4b, 5b and 6b offered a unique possibility to elucidate the influence of particular packing arrangements on dye aggregate interactions with light. In particular, it can be investigated how exciton coupling of the dyes' transition dipole moments and fluorescence properties are affected. In this context, the spectroscopic properties were investigated in thin film, which revealed a strong bathochromic shift of the absorption maxima compared to the monomers in solution in dependence on the number of strands for PBIs 4-6b in contrast to PBI 3b (Figure 8.2e). The same tendency was observed for the respective aggregates in MCH solution. The spectral changes obtained during concentration- and temperature-dependent UV-Vis absorption studies verified the formation of J-aggregates in MCH solution and solid state. The respective aggregates are highly likely formed via a nucleation-elongation growth mechanism. Appliance of Kasha's exciton theory on the supramolecular aggregates revealed different contributions of H- and J-type coupling for the oligo-stranded helices. Under these considerations, it delivered an explanation for the absorption and fluorescence properties of the assemblies and declares the "best" J-aggregate for the double stranded arrangement of PBI 6b with purely negative couplings among neighbour molecules and a quantum yield above 74 \% of the aggregates in MCH solution. With this H-bonded PBI-based library approach of twelve derivatives it could be shown how molecular engineering of perylene bisimide dyes can be used to design defined, complex supramolecular assemblies with unprecedented packing patterns and concomitant intriguing spectroscopic properties. So far, the formation of defined liquid crystalline supramolecular structures of tetra-bay substituted PBIs by double H-bonding between free imide moieties and pi-pi interactions between the chromophores was demonstrated. The impact of the H-bonds on the molecular arrangement was investigated in the next part of this thesis. In this regard, PBIs 7 and 8 bearing a methyl or cyclohexyl group at the imide position (Figure 8.3a) were synthesized and compared to PBI 4c. The soft character of the solid state for PBIs 7 and 8 was confirmed by POM, DSC and X-ray analysis. The X-ray studies further revealed for both PBIs a change of the molecular assembly towards helical columnar structures of conventional pi-stacked chromophores (Figure 8.3b) when the directed H-bonds cannot contribute as noncovalent interactions to the assembly formation. Temperature-dependent UV-Vis absorption studies demonstrated the importance of H-bonding in MCH solution in the way that the formation of J-aggregates as for PBI 4c could not be observed for the imide substituted molecules. In the next step, the spectroscopic properties in thin film were investigated. For PBI 7 a J-type band and fluorescence spectra with an enlarged Stokes shift and increased fluorescence lifetime of 11.4 ns, compared to PBI 4c, was obtained, suggesting the generation of excimer type emission by considering the assumed conventional stacking of rotational displaced molecules from X-ray analysis. With polarized UV-Vis absorption experiments the orientation of the molecules perpendicular to the shearing direction and subsequently to the columnar axis was confirmed. These diverse investigations clearly demonstrated the imperative of H-bonds for stable, defined, LC J-aggregates with the transition dipole moments parallel to the columnar axis. With PBIs 7 and 8 it is impressively shown how small changes in the molecular structure influence the molecular arrangement dependent on the cooperation of non-covalent interactions like H-bonding and pi-pi stacking. In the last part of this thesis the generation of two-dimensional LC arrangements is presented. Since tetra-bay substituted PBIs lead always to twisted cores preventing lamellar arrangement, here 1,7-disubstitution and the simultaneous retention of the free imide positions was chosen to generate LC lamellar phases of PBIs 9a, 9b and 10 (Figure 8.4a). This molecular design was expected to form planar perylene cores that can strongly interact by pi-pi stacking and H-bonding. POM, DSC and X-ray investigations of the compounds suggest lamellar LC phases for PBIs 9a and 9b and a soft phase for PBI 10. In this regard, the goal of the formation of LC lamellar phase of PBIs could be attained. The change from dendrons with n-C12-alkoxy chains to large fork-like mesogens like in 9b clearly changed the phase properties. PBI 9b exhibits the lowest clearing point, high phase stability, least viscosity, easy shearability at room temperature and phase transitions between lamellar and Colh phases dependent on temperature. The formation of H-bonds parallel to the layers was demonstrated by polarized FT-IR experiments for all three PBIs. Concentration-dependent UV-Vis absorption studies revealed the formation of a J-type aggregate, which seems to exhibit an overall two-dimensional structure. With STM investigations the formation of lamellar structures from drop-casted 9a and 10 solutions in 1-phenyloctane on HOPG surface could be observed. Figure 8.4b illustrates a schematic possible arrangement of the molecules in the layers (here exemplarily demonstrated for PBI 9a), which has to be further confirmed by modelling and simulations. Unfortunately, fluorescence investigations of the thin films revealed non- or only slightly emissive LC states, which make them negligible for photonic applications. Nevertheless, the synthesized and analyzed compounds might be an inspiration for further investigations on the path to two-dimensional exciton transport for photonic devices.},
  subject      = {Fl{\"u}ssigkristall},
  language  = {en}
}