TY - JOUR A1 - Spenst, Peter A1 - Young, Ryan M. A1 - Wasielewski, Michael R. A1 - Würthner, Frank T1 - Guest and solvent modulated photo-driven charge separation and triplet generation in a perylene bisimide cyclophane JF - Chemical Science N2 - Cofacial positioning of two perylene bisimide (PBI) chromophores at a distance of 6.5 angstrom in a cyclophane structure prohibits the otherwise common excimer formation and directs photoexcited singlet state relaxation towards intramolecular symmetry-breaking charge separation (τ\(_{CS}\) = 161 +/- 4 ps) in polar CH\(_2\)Cl\(_2\), which is thermodynamically favored with a Gibbs free energy of ΔG\(_{CS}\) = -0.32 eV. The charges then recombine slowly in τ\(_{CR}\) = 8.90 +/- 0.06 ns to form the PBI triplet excited state, which can be used subsequently to generate singlet oxygen in 27% quantum yield. This sequence of events is eliminated by dissolving the PBI cyclophane in non-polar toluene, where only excited singlet state decay occurs. In contrast, complexation of electron-rich aromatic hydrocarbons by the host PBI cyclophane followed by photoexcitation of PBI results in ultrafast electron transfer (<10 ps) from the guest to the PBI in CH\(_2\)Cl\(_2\). The rate constants for charge separation and recombination increase as the guest molecules become easier to oxidize, demonstrating that charge separation occurs close to the peak of the Marcus curve and the recombination lies far into the Marcus inverted region. KW - photoinduced electron transfer KW - Marcus inverted region KW - cyclic perylene bisimide KW - PBI cyclophane Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191252 VL - 7 IS - 8 ER - TY - JOUR A1 - Walter, T. A1 - Collenburg, L. A1 - Japtok, L. A1 - Kleuser, B. A1 - Schneider-Schaulies, S. A1 - Müller, N. A1 - Becam, J. A1 - Schubert-Unkmeir, A. A1 - Kong, J. N. A1 - Bieberich, E. A1 - Seibel, J. T1 - Incorporation and visualization of azido-functionalized N-oleoyl serinol in Jurkat cells, mouse brain astrocytes, 3T3 fibroblasts and human brain microvascular endothelial cells JF - Chemical Communications N2 - The synthesis and biological evaluation of azido-N-oleoyl serinol is reported. It mimicks biofunctional lipid ceramides and has shown to be capable of click reactions for cell membrane imaging in Jurkat and human brain microvascular endothelial cells. KW - Ceramide KW - Apoptosis KW - Golgi KW - N-oleoyl serinol KW - Jurkat cells Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191263 VL - 52 IS - 55 ER - TY - JOUR A1 - Gershberg, Jana A1 - Fennel, Franziska A1 - Rehm, Thomas H. A1 - Lochbrunner, Stefan A1 - Würthner, Frank T1 - Anti-cooperative supramolecular polymerization: a new K\(_2\)-K model applied to the self-assembly of perylene bisimide dye proceeding via well-defined hydrogen-bonded dimers JF - Chemical Science N2 - A perylene bisimide dye bearing amide functionalities at the imide positions derived from amino acid L-alanine and a dialkoxy-substituted benzyl amine self-assembles into tightly bound dimers by π-π-stacking and hydrogen bonding in chloroform. In less polar or unpolar solvents like toluene and methylcyclohexane, and in their mixtures, these dimers further self-assemble into extended oligomeric aggregates in an anti-cooperative process in which even numbered aggregates are highly favoured. The stepwise transition from dimers into oligomers can not be properly described by conventional K\(_2\)-K model, and thus a new K\(_2\)-K aggregation model has been developed, which interpretes the present anti-cooperative supramolecular polymerization more appropriately. The newly developed K\(_2\)-K model will be useful to describe self-assembly processes of a plethora of other π-conjugated molecules that are characterized by a favored dimer species. KW - π–π Stacking KW - nucleation elongation KW - upramolecular polymerization process KW - dimerization KW - K2–K model Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191428 VL - 7 IS - 3 ER - TY - JOUR A1 - Kar, Haridas A1 - Gehrig, Dominik W. A1 - Allampally, Naveen Kumar A1 - Fernández, Gustavo A1 - Laquai, Frédéric A1 - Ghosh, Suhrit T1 - Cooperative supramolecular polymerization of an amine-substituted naphthalene-diimide and its impact on excited state photophysical properties JF - Chemical Science N2 - A donor-acceptor-donor (D-A-D) type naphthalene-diimide (NDI-H) chromophore exhibits highly cooperative J-aggregation leading to nanotubular self-assembly and gelation in n-decane, as demonstrated by UV/Vis, FT-IR, photoluminescence and microscopy studies. Analysis of temperature-dependent UV/Vis spectra using the nucleation-elongation model and FT-IR data reveals the molecular origin of the cooperative nature of the self-assembly. The supramolecular polymerization is initiated by H-bonding up to a degree of polymerization similar to 20-25, which in a subsequent elongation step promotes J-aggregation in orthogonal direction leading to possibly a sheet-like structure that eventually produces nanotubes. Time-resolved fluorescence and absorption measurements demonstrate that such a tubular assembly enables very effective delocalization of excited states resulting in a remarkably prolonged excited state lifetime. KW - nanotube KW - supramolecular polymerization KW - NDI-H KW - UV/Vis spectroscopy KW - FT-IR spectroscopy KW - transient absorption KW - nucleation-elongation model Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191459 VL - 7 IS - 2 ER - TY - THES A1 - Sapotta, Meike T1 - Perylene Bisimide Cyclophanes: Recognition of Alkaloids, Aggregation Behavior in Aqueous Environment and Guest-Mediated Chirality Transfer T1 - Perylenbisimidcyclophane: Alkaloiderkennung, Aggregationsverhalten in wässriger Umgebung und gastvermittelter Chiralitätstransfer N2 - Inspired by the fact that sufficient solubility in aqueous media can be achieved by functional substitution of perylene bisimides (PBIs) with polar groups, one of the essential aims of this thesis was the design and successful synthesis of the new water-soluble PBI cyclophanes [2PBI]-1m and [2PBI]-1p, which are appended with branched, hydrophilic oligoethylene glycol (OEG) chains. Subsequently, the focus was set on the elucidation of properties of PBI cyclophane hosts which are also of relevance for recognition processes in biological systems. The performance of the new amphiphilic PBI cyclophane [2PBI]-1p as synthetic receptors for various natural aromatic alkaloids in aqueous media was thoroughly investigated. Alkaloids represent a prominent class of ubiquitous nitrogen containing natural compounds with a great structural variety and diverse biological activity. As of yet, no chromophore host acting as a molecular probe for a range of alkaloids such as harmine or harmaline is known. In addition, the self-association behavior of cyclophane host [2PBI]-1m and its reference monomer in water was studied in order to gain insights into the thermodynamic driving forces affecting the self-assembly process of these two PBI systems in aqueous environment. Moreover, the chirality transfer upon guest binding previously observed for a PBI cyclophane was investigated further. The assignment of the underlying mechanism of guest recognition to either the induced fit or conformational selection model was of particular interest. N2 - Diese Arbeit befasste sich mit der Erforschung neuer Eigenschaften von Perylenbisimid-cyclophanwirten, zum Beispiel der Gast-Komplexierung in wässriger Umgebung (Kapitel 3.2) oder dem Einfluss von Wasser beim Selbstassemblierungsprozess einer dieser Wirte in Wasser (Kapitel 3.3). Weiterhin wurden der Chiralitätstransfer durch Gasterkennung und das der Wirt-Gast-Komplexbildung zugrunde liegende mechanistische Modell untersucht (Kapitel 3.4). ... KW - Supramolekulare Chemie KW - Perylenderivate KW - Wirt-Gast-Beziehung KW - Host-Guest-Chemistry KW - Self-Assembly in Water KW - Chirality Transfer KW - Chiralität KW - Selbstorganisation KW - Organische Chemie Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200028 ER - TY - JOUR A1 - Kraft, Andreas A1 - Stangl, Johannes A1 - Krause, Ana-Maria A1 - Müller-Buschbaum, Klaus A1 - Beuerle, Florian T1 - Supramolecular frameworks based on [60]fullerene hexakisadducts JF - Beilstein Journal of Organic Chemistry N2 - [60]Fullerene hexakisadducts possessing 12 carboxylic acid side chains form crystalline hydrogen-bonding frameworks in the solid state. Depending on the length of the linker between the reactive sites and the malonate units, the distance of the [60]fullerene nodes and thereby the spacing of the frameworks can be controlled and for the most elongated derivative, continuous channels are obtained within the structure. Stability, structural integrity and porosity of the material were investigated by powder X-ray diffraction, thermogravimetry and sorption measurements. KW - chemistry KW - fullerenes KW - hexakisadducts KW - hydrogen bonding KW - porous materials KW - structure elucidation Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171996 VL - 13 ER - TY - JOUR A1 - Wächtler, Maria A1 - Kübel, Joachim A1 - Barthelmes, Kevin A1 - Winter, Andreas A1 - Schmiedel, Alexander A1 - Pascher, Torbjörn A1 - Lambert, Christoph A1 - Schubert, Ulrich S. A1 - Dietzek, Benjamin T1 - Energy transfer and formation of long-lived \(^3\)MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands JF - Physical Chemistry Chemical Physics N2 - Multimetallic complexes with extended and highly conjugated bis-2,2':6',2''-terpyridyl bridging ligands, which present building blocks for coordination polymers, are investigated with respect to their ability to act as light-harvesting antennae. The investigated species combine Ru(II)- with Os(II)- and Fe(II)-terpyridyl chromophores, the latter acting as energy sinks. Due to the extended conjugated system the ligands are able to prolong the lifetime of the \(^3\)MLCT states compared to unsubstituted terpyridyl species by delocalization and energetic stabilization of the \(^3\)MLCT states. This concept is applied for the first time to Fe(II) terpyridyl species and results in an exceptionally long lifetime of 23 ps for the Fe(II) \(^3\)MLCT state. While partial energy (>80%) transfer is observed between the Ru(II) and Fe(II) centers with a time-constant of 15 ps, excitation energy is transferred completely from the Ru(II) to the Os(II) center within the first 200 fs after excitation. KW - polypyridyl complexes KW - bis-terpyridyl ligands KW - multimetallic complexes KW - metal-to-ligand charge transfer (MLCT) KW - RU-(II) complexes KW - Ru(II)–Fe(II)–Ru(II) complex Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191041 VL - 18 IS - 4 ER - TY - JOUR A1 - Fayez, Shaimaa A1 - Feineis, Doris A1 - Mudogo, Virima A1 - Awale, Suresh A1 - Bringmann, Gerhard T1 - Ancistrolikokines E-H and related 5,8\('\)-coupled naphthylisoquinoline alkaloids from the Congolese liana \(Ancistrocladus\) \(likoko\) with antiausterity activities against PANC-1 human pancreatic cancer cells JF - RSC Advances N2 - A striking feature of the metabolite profile of \(Ancistrocladus\) \(likoko\) (Ancistrocladaceae) is the exclusive production of 5,8\('\)-linked naphthylisoquinoline alkaloids varying in their OMe/OH substitution patterns and in the hydrogenation degree in their isoquinoline portions. Here we present nine new compounds of this coupling type isolated from the twigs of this remarkable Central African liana. Three of them, the ancistrolikokines E (9), E\(_2\) (10), and F (11), are the first 5,8\('\)-linked naphthyldihydroisoquinolines found in nature with \(R\)-configuration at C-3. The fourth new metabolite, ancistrolikokine G (12), is so far the only representative of the 5,8\('\)-coupling type that belongs to the very rare group of alkaloids with a fully dehydrogenated isoquinoline portion. Moreover, five new \(N\)-methylated naphthyltetrahydroisoquinolines, named ancistrolikokines A\(_2\) (13), A\(_3\) (14), C\(_2\) (5), H (15), and H\(_2\) (16) are presented, along with six known 5,8\('\)-linked alkaloids, previously identified in related African \(Ancistrocladus\) species, now found for the first time in \(A.\) \(likoko\). The structural elucidation was achieved by spectroscopic analysis (HRESIMS, 1D and 2D NMR) and by chemical (oxidative degradation) and chiroptical (electronic circular dichroism) methods. The new ancistrolikokines showed moderate to good preferential cytotoxic activities towards pancreatic PANC-1 cells in nutrient-deprived medium (NDM), without causing toxicity under normal, nutrient-rich conditions, with ancistrolikokine H\(_2\) (16) being the most potent compound. KW - chemistry KW - Ancistrocladus likoko KW - alkaloids KW - bioactive compound KW - anti-cancer-agent KW - pancreatic cancer KW - naphthylisoquinoline alkaloid KW - spectroscopic analysis Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172008 VL - 7 IS - 85 ER - TY - JOUR A1 - Kokic, Goran A1 - Hillen, Hauke S. A1 - Tegunov, Dimitry A1 - Dienermann, Christian A1 - Seitz, Florian A1 - Schmitzova, Jana A1 - Farnung, Lucas A1 - Siewert, Aaron A1 - Höbartner, Claudia A1 - Cramer, Patrick T1 - Mechanism of SARS-CoV-2 polymerase stalling by remdesivir JF - Nature Communications N2 - Remdesivir is the only FDA-approved drug for the treatment of COVID-19 patients. The active form of remdesivir acts as a nucleoside analog and inhibits the RNA-dependent RNA polymerase (RdRp) of coronaviruses including SARS-CoV-2. Remdesivir is incorporated by the RdRp into the growing RNA product and allows for addition of three more nucleotides before RNA synthesis stalls. Here we use synthetic RNA chemistry, biochemistry and cryoelectron microscopy to establish the molecular mechanism of remdesivir-induced RdRp stalling. We show that addition of the fourth nucleotide following remdesivir incorporation into the RNA product is impaired by a barrier to further RNA translocation. This translocation barrier causes retention of the RNA 3ʹ-nucleotide in the substrate-binding site of the RdRp and interferes with entry of the next nucleoside triphosphate, thereby stalling RdRp. In the structure of the remdesivir-stalled state, the 3ʹ-nucleotide of the RNA product is matched and located with the template base in the active center, and this may impair proofreading by the viral 3ʹ-exonuclease. These mechanistic insights should facilitate the quest for improved antivirals that target coronavirus replication. KW - SARS-CoV-2 polymerase KW - Remdesivir KW - RNA-dependent RNA polymerase KW - Molecular mechanism KW - Biochemistry KW - Cryoelectron microscopy KW - RNA Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-220979 VL - 12 ER - TY - JOUR A1 - Suliman, Salwa A1 - Sun, Yang A1 - Pedersen, Torbjorn O. A1 - Xue, Ying A1 - Nickel, Joachim A1 - Waag, Thilo A1 - Finne-Wistrand, Anna A1 - Steinmüller-Nethl, Doris A1 - Krueger, Anke A1 - Costea, Daniela E. A1 - Mustafa, Kamal T1 - In vivo host response and degradation of copolymer scaffolds functionalized with nanodiamonds and bone morphogenetic protein 2 JF - Advanced Healthcare Materials N2 - The aim is to evaluate the effect of modifying poly[(L-lactide)-co-(epsilon-caprolactone)] scaffolds (PLCL) with nanodiamonds (nDP) or with nDP+physisorbed BMP-2 (nDP+BMP-2) on in vivo host tissue response and degradation. The scaffolds are implanted subcutaneously in Balb/c mice and retrieved after 1, 8, and 27 weeks. Molecular weight analysis shows that modified scaffolds degrade faster than the unmodified. Gene analysis at week 1 shows highest expression of proinflammatory markers around nDP scaffolds; although the presence of inflammatory cells and foreign body giant cells is more prominent around the PLCL. Tissue regeneration markers are highly expressed in the nDP+BMP-2 scaffolds at week 8. A fibrous capsule is detectable by week 8, thinnest around nDP scaffolds and at week 27 thickest around PLCL scaffolds. mRNA levels of ALP, COL1 alpha 2, and ANGPT1 are signifi cantly upregulating in the nDP+BMP-2 scaffolds at week 1 with ectopic bone seen at week 8. Even when almost 90% of the scaffold is degraded at week 27, nDP are observable at implantation areas without adverse effects. In conclusion, modifying PLCL scaffolds with nDP does not aggravate the host response and physisorbed BMP-2 delivery attenuates infl ammation while lowering the dose of BMP-2 to a relatively safe and economical level. KW - inflammatory response KW - biocompatibility KW - BMP-2 delivery KW - inflammation KW - tissue engineering Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189764 VL - 5 IS - 6 ER -