@article{BakirciFrankGumbeletal.2021, author = {Bakirci, Ezgi and Frank, Andreas and Gumbel, Simon and Otto, Paul F. and F{\"u}rsattel, Eva and Tessmer, Ingrid and Schmidt, Hans-Werner and Dalton, Paul D.}, title = {Melt Electrowriting of Amphiphilic Physically Crosslinked Segmented Copolymers}, series = {Macromolecular Chemistry and Physics}, volume = {222}, journal = {Macromolecular Chemistry and Physics}, number = {22}, doi = {10.1002/macp.202100259}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257572}, year = {2021}, abstract = {Various (AB)\(_{n}\) and (ABAC)\(_{n}\) segmented copolymers with hydrophilic and hydrophobic segments are processed via melt electrowriting (MEW). Two different (AB)\(_{n}\) segmented copolymers composed of bisurea segments and hydrophobic poly(dimethyl siloxane) (PDMS) or hydrophilic poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEG-PPO) segments, while the amphiphilic (ABAC)\(_{n}\) segmented copolymers consist of bisurea segments in the combination of hydrophobic PDMS segments and hydrophilic PPO-PEG-PPO segments with different ratios, are explored. All copolymer compositions are processed using the same conditions, including nozzle temperature, applied voltage, and collector distance, while changes in applied pressure and collector speed altered the fiber diameter in the range of 7 and 60 µm. All copolymers showed excellent processability with MEW, well-controlled fiber stacking, and inter-layer bonding. Notably, the surfaces of all four copolymer fibers are very smooth when visualized using scanning electron microscopy. However, the fibers show different roughness demonstrated with atomic force microscopy. The non-cytotoxic copolymers increased L929 fibroblast attachment with increasing PDMS content while the different copolymer compositions result in a spectrum of physical properties.}, language = {en} } @article{BialasZitzlerKunkelKirchneretal.2016, author = {Bialas, David and Zitzler-Kunkel, Andr{\´e} and Kirchner, Eva and Schmidt, David and W{\"u}rthner, Frank}, title = {Structural and quantum chemical analysis of exciton coupling in homo- and heteroaggregate stacks of merocyanines}, series = {Nature Communications}, volume = {7}, journal = {Nature Communications}, doi = {10.1038/ncomms12949}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170200}, year = {2016}, abstract = {Exciton coupling is of fundamental importance and determines functional properties of organic dyes in (opto-)electronic and photovoltaic devices. Here we show that strong exciton coupling is not limited to the situation of equal chromophores as often assumed. Quadruple dye stacks were obtained from two bis(merocyanine) dyes with same or different chromophores, respectively, which dimerize in less-polar solvents resulting in the respective homo- and heteroaggregates. The structures of the quadruple dye stacks were assigned by NMR techniques and unambiguously confirmed by single-crystal X-ray analysis. The heteroaggregate stack formed from the bis(merocyanine) bearing two different chromophores exhibits remarkably different ultraviolet/vis absorption bands compared with those of the homoaggregate of the bis(merocyanine) comprising two identical chromophores. Quantum chemical analysis based on an extension of Kasha's exciton theory appropriately describes the absorption properties of both types of stacks revealing strong exciton coupling also between different chromophores within the heteroaggregate.}, language = {en} } @article{FarrellGrandeSchmidtetal.2019, author = {Farrell, Jeffrey M. and Grande, Vincenzo and Schmidt, David and W{\"u}rthner, Frank}, title = {A Highly Warped Heptagon-Containing sp\(^2\) Carbon Scaffold via Vinylnaphthyl π-Extension}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {46}, doi = {10.1002/anie.201909975}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206682}, pages = {16504-16507}, year = {2019}, abstract = {A new strategy is demonstrated for the synthesis of warped, negatively curved, all-sp\(^2\)-carbon π-scaffolds. Multifold C-C coupling reactions are used to transform a polyaromatic borinic acid into a saddle-shaped polyaromatic hydrocarbon (2 ) bearing two heptagonal rings. Notably, this Schwarzite substructure is synthesized in only two steps from an unfunctionalized alkene. A highly warped structure of 2 was revealed by X-ray crystallographic studies and pronounced flexibility of this π-scaffold was ascertained by experimental and computational studies. Compound 2 exhibits excellent solubility, visible range absorption and fluorescence, and readily undergoes two reversible one-electron oxidations at mild potentials.}, language = {en} } @article{HocheSchulzDietrichetal.2019, author = {Hoche, Joscha and Schulz, Alexander and Dietrich, Lysanne Monika and Humeniuk, Alexander and Stolte, Matthias and Schmidt, David and Brixner, Tobias and W{\"u}rthner, Frank and Mitric, Roland}, title = {The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes}, series = {Chemical Science}, volume = {10}, journal = {Chemical Science}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-198707}, pages = {11013}, year = {2019}, abstract = {Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM),i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran (DCBT). We measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law.This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier.}, language = {en} } @article{KarakayaBiderFranketal.2022, author = {Karakaya, Emine and Bider, Faina and Frank, Andreas and Teßmar, J{\"o}rg and Sch{\"o}bel, Lisa and Forster, Leonard and Schr{\"u}fer, Stefan and Schmidt, Hans-Werner and Schubert, Dirk Wolfram and Blaeser, Andreas and Boccaccini, Aldo R. and Detsch, Rainer}, title = {Targeted printing of cells: evaluation of ADA-PEG bioinks for drop on demand approaches}, series = {Gels}, volume = {8}, journal = {Gels}, number = {4}, issn = {2310-2861}, doi = {10.3390/gels8040206}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-267317}, year = {2022}, abstract = {A novel approach, in the context of bioprinting, is the targeted printing of a defined number of cells at desired positions in predefined locations, which thereby opens up new perspectives for life science engineering. One major challenge in this application is to realize the targeted printing of cells onto a gel substrate with high cell survival rates in advanced bioinks. For this purpose, different alginate-dialdehyde—polyethylene glycol (ADA-PEG) inks with different PEG modifications and chain lengths (1-8 kDa) were characterized to evaluate their application as bioinks for drop on demand (DoD) printing. The biochemical properties of the inks, printing process, NIH/3T3 fibroblast cell distribution within a droplet and shear forces during printing were analyzed. Finally, different hydrogels were evaluated as a printing substrate. By analysing different PEG chain lengths with covalently crosslinked and non-crosslinked ADA-PEG inks, it was shown that the influence of Schiff's bases on the viscosity of the corresponding materials is very low. Furthermore, it was shown that longer polymer chains resulted in less stable hydrogels, leading to fast degradation rates. Several bioinks highly exhibit biocompatibility, while the calculated nozzle shear stress increased from approx. 1.3 and 2.3 kPa. Moreover, we determined the number of cells for printed droplets depending on the initial cell concentration, which is crucially needed for targeted cell printing approaches.}, language = {en} } @article{MahlShoyamaKrauseetal.2020, author = {Mahl, Magnus and Shoyama, Kazutaka and Krause, Ana-Maria and Schmidt, David and W{\"u}rthner, Frank}, title = {Base-Assisted Imidization: A Synthetic Method for the Introduction of Bulky Imide Substituents to Control Packing and Optical Properties of Naphthalene and Perylene Imides}, series = {Angewandte Chemie International Edition}, volume = {59}, journal = {Angewandte Chemie International Edition}, number = {32}, doi = {10.1002/anie.202004965}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218246}, pages = {13401 -- 13405}, year = {2020}, abstract = {We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho,ortho-diaryl- and ortho,ortho-dialkynylaniline derivatives. This imidization method uses n-butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single-crystal X-ray diffraction analyses reveal dimeric packing motifs for monoimides, while two-side shielded bisimides crystallize in isolated molecules without close π-π-interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state.}, language = {en} } @article{MechauFrankBakircietal.2021, author = {Mechau, Jannik and Frank, Andreas and Bakirci, Ezgi and Gumbel, Simon and Jungst, Tomasz and Giesa, Reiner and Groll, J{\"u}rgen and Dalton, Paul D. and Schmidt, Hans-Werner}, title = {Hydrophilic (AB)\(_{n}\) Segmented Copolymers for Melt Extrusion-Based Additive Manufacturing}, series = {Macromolecular Chemistry and Physics}, volume = {222}, journal = {Macromolecular Chemistry and Physics}, number = {1}, doi = {10.1002/macp.202000265}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224513}, year = {2021}, abstract = {Several manufacturing technologies beneficially involve processing from the melt, including extrusion-based printing, electrospinning, and electrohydrodynamic jetting. In this study, (AB)\(_{n}\) segmented copolymers are tailored for melt-processing to form physically crosslinked hydrogels after swelling. The copolymers are composed of hydrophilic poly(ethylene glycol)-based segments and hydrophobic bisurea segments, which form physical crosslinks via hydrogen bonds. The degree of polymerization was adjusted to match the melt viscosity to the different melt-processing techniques. Using extrusion-based printing, a width of approximately 260 µm is printed into 3D constructs, with excellent interlayer bonding at fiber junctions, due to hydrogen bonding between the layers. For melt electrospinning, much thinner fibers in the range of about 1-15 µm are obtained and produced in a typical nonwoven morphology. With melt electrowriting, fibers are deposited in a controlled way to well-defined 3D constructs. In this case, multiple fiber layers fuse together enabling constructs with line width in the range of 70 to 160 µm. If exposed to water the printed constructs swell and form physically crosslinked hydrogels that slowly disintegrate, which is a feature for soluble inks within biofabrication strategies. In this context, cytotoxicity tests confirm the viability of cells and thus demonstrating biocompatibility of this class of copolymers.}, language = {en} } @article{MezaChinchaLindnerSchindleretal.2020, author = {Meza-Chincha, Ana-Lucia and Lindner, Joachim O. and Schindler, Dorothee and Schmidt, David and Krause, Ana-Maria and R{\"o}hr, Merle I. S. and Mitrić, Roland and W{\"u}rthner, Frank}, title = {Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation}, issn = {2041-6539}, doi = {10.1039/d0sc01097a}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204653}, year = {2020}, abstract = {Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites.}, language = {en} } @article{PinkawaAebersoldBoehmeretal.2021, author = {Pinkawa, Michael and Aebersold, Daniel M. and B{\"o}hmer, Dirk and Flentje, Michael and Ghadjar, Pirus and Schmidt-Hegemann, Nina-Sophie and H{\"o}cht, Stefan and H{\"o}lscher, Tobias and M{\"u}ller, Arndt-Christian and Niehoff, Peter and Sedlmayer, Felix and Wolf, Frank and Zamboglou, Constantinos and Zips, Daniel and Wiegel, Thomas}, title = {Radiotherapy in nodal oligorecurrent prostate cancer}, series = {Strahlentherapie und Onkologie}, volume = {197}, journal = {Strahlentherapie und Onkologie}, number = {7}, issn = {0179-7158}, doi = {10.1007/s00066-021-01778-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-307763}, pages = {575-580}, year = {2021}, abstract = {Objective The current article encompasses a literature review and recommendations for radiotherapy in nodal oligorecurrent prostate cancer. Materials and methods A literature review focused on studies comparing metastasis-directed stereotactic ablative radiotherapy (SABR) vs. external elective nodal radiotherapy (ENRT) and studies analyzing recurrence patterns after local nodal treatment was performed. The DEGRO Prostate Cancer Expert Panel discussed the results and developed treatment recommendations. Results Metastasis-directed radiotherapy results in high local control (often > 90\% within a follow-up of 1-2 years) and can be used to improve progression-free survival or defer androgen deprivation therapy (ADT) according to prospective randomized phase II data. Distant progression after involved-node SABR only occurs within a few months in the majority of patients. ENRT improves metastases-free survival rates with increased toxicity in comparison to SABR according to retrospective comparative studies. The majority of nodal recurrences after initial local treatment of pelvic nodal metastasis are detected within the true pelvis and common iliac vessels. Conclusion ENRT with or without a boost should be preferred to SABR in pelvic nodal recurrences. In oligometastatic prostate cancer with distant (extrapelvic) nodal recurrences, SABR alone can be performed in selected cases. Application of additional systemic treatments should be based on current guidelines, with ADT as first-line treatment for hormone-sensitive prostate cancer. Only in carefully selected patients can radiotherapy be initially used without additional ADT outside of the current standard recommendations. Results of (randomized) prospective studies are needed for definitive recommendations.}, language = {en} } @article{SchmidtStolteSuessetal.2019, author = {Schmidt, David and Stolte, Matthias and S{\"u}ß, Jasmin and Liess, Dr. Andreas and Stepanenko, Vladimir and W{\"u}rthner, Frank}, title = {Protein-like enwrapped perylene bisimide chromophore as bright microcrystalline emitter material}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {38}, doi = {10.1002/ange.201907618}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204809}, pages = {13385-13389}, year = {2019}, abstract = {Strongly emissive solid-state materials are mandatory components for many emerging optoelectronic technologies, but fluorescence is often quenched in the solid state owing to strong intermolecular interactions. The design of new organic pigments, which retain their optical properties despite their high tendency to crystallize, could overcome such limitations. Herein, we show a new material with monomer-like absorption and emission profiles as well as fluorescence quantum yields over 90 \% in its crystalline solid state. The material was synthesized by attaching two bulky tris(4-tert-butylphenyl)phenoxy substituents at the perylene bisimide bay positions. These substituents direct a packing arrangement with full enwrapping of the chromophore and unidirectional chromophore alignment within the crystal lattice to afford optical properties that resemble those of their natural pigment counterparts, in which chromophores are rigidly embedded in protein environments.}, language = {en} }