TY  - JOUR
A1  - Christl, Manfred
A1  - Schreck, Michael
T1  - 1,2,3,5,8,8a-Hexahydronaphthalin aus 1,2-Cyclohexadien
N2  - Reaktionen von 1,3-Butadien und einigen seiner Methylderivate mit 1a und 1- Methyl-1,2-cyclohexadien 1b sowie den Übergang der [2 + 2]-Cycloaddukte 2 und 3 in das bisher unbekannte 1,2,3,5,8,8a-HexahydronaphthaJin 4a und einige seiner Methylderivate
KW  - Chemie
KW  - Butadien
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-31656
ER  - 
TY  - JOUR
A1  - Christl, Manfred
A1  - Braun, Martin
A1  - Müller, Germar
T1  - 1,2,4-Cyclohexatriene, an Isobenzene, and Bicyclo[4.4.0)deca-1,3,5,7,8-pentaene, an Isonaphthalene: Generation and Trapping Reactions
N2  - No abstract available
KW  - Organische Chemie
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58639
ER  - 
TY  - JOUR
A1  - Mützel, Carina
A1  - Farrell, Jeffrey M.
A1  - Shoyama, Kazutaka
A1  - Würthner, Frank
T1  - 12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon
JF  - Angewandte Chemie International Edition
N2  - Herein we devise and execute a new synthesis of a pristine boron-doped nanographene. Our target boron-doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B-doping arrangement. Our synthesis of this target, a doubly B-doped hexabenzopentacene (B\(_{2}\)-HBP), employs six net C−H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr\(_{3}\)/AlCl\(_{3}\)/2,6-dichloropyridine-mediated C−H borylation steps. As predicted by our calculations, B\(_{2}\)-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B\(_{2}\)-HBP possesses a very low LUMO level, showing two reversible reductions at −1.00 V and −1.17 V vs. Fc\(^{+}\)/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B-doped polycyclic aromatic hydrocarbons.
KW  - aromaticity
KW  - polycycles
KW  - pentacene
KW  - near infrared emitter
KW  - boron
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318808
VL  - 61
IS  - 8
ER  - 
TY  - JOUR
A1  - Gleiter, Rolf
A1  - Bischof, Peter
A1  - Gubernator, Klaus
A1  - Christl, Manfred
A1  - Schwager, Luis
A1  - Vogel, Pierre
T1  - 2,3-Bis(methylene)bicyclo[2.1.1]hexane and 3,4-Bis(methylene)tricyclo[3.1.0.0\(^{2,6}\)]hexane : Interaction between a π System and a Cyclobutane or Bicyclobutane Moiety
N2  - The He (I) photoelectron spectra of 2-bicyclo[2.1.l]hexene (1), 2,3-bis(methylene)bicyclo[2.1.l]hexane (3), and 3,4-bis(methylene)tricyclo[3.l.O.0\(^{2.6}\)]hexane (4) have been investigated. The assignment given is based on a ZDO model and semiempirical calculations. Tagether with the PE data of benzvalene (2), the reported data allow a comparison between 1-2 and 3-4. This yields a measure of the interactions between 8 cyclobutane or 8 bicyclobutane moiety and a double bond system within a ZDO model. The resonance integral found in the case of 1 and 3 amounts to -1.9 eV, that for 2 and 4, to -2.3 eV. The investigations furthermore reveal that the electronic factors which contribute to the higher reactivity of the bicyclobutane compounds amount to 5 kcal/mol.
KW  - Chemie
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-31845
ER  - 
TY  - JOUR
A1  - Lanzendörfer, Franz
A1  - Christl, Manfred
T1  - 3,4-Bismethylentricyclo[3.1.0.0<sup>2,6</sup>]hexan - Synthese und Diels-Alder-Addition an Tetracyanethylen
N2  - No abstract available
Y1  - 1983
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30263
ER  - 
TY  - JOUR
A1  - Christl, Manfred
A1  - Leß, Roland
A1  - Müller, Heinrich
T1  - 6,7-Dimethylene-2,4-diphenylbicyclo[3.2.l]oct-3-en-2-yl Anion : A Test for the Origin of the Unusual Properties of the Bicyclo[3.2.l]octa-3,6-dien-2-yl Anion
N2  - No abstract available
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-31547
ER  - 
TY  - JOUR
A1  - Christl, Manfred
A1  - Brunn, E.
A1  - Roth, W. R.
A1  - Lennartz, H.-W.
T1  - 7-Methyl- and 7-Phenylcyclohepta-1,3,5-trienes from Benzvalene Via 3,3a,4,5,6,6a-Hexahydro-4,5,6-methenocyclopentapyrazoles and Tetracyclo[4.1.0.0\(^{2,4}\).0\(^{3,5}\)]heptanes
N2  - No abstract available
KW  - Organische Chemie
Y1  - 1989
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58471
ER  - 
TY  - JOUR
A1  - Christl, Manfred
A1  - Warren, J. D.
A1  - Hawkins, B. L.
A1  - Roberts, J. D.
T1  - \(^{13}\)C and \(^{15}\)N Nuclear Magnetic Resonance Spectroscopy of Nitrile Oxides and Related Reaction Products : Unexpected \(^{13}\)C and \(^{15}\)N Nuclear Magnetic Resonance Parameters of 2,4,6-Trimethylbenzonitrile Oxide
N2  - No abstract available
KW  - Organische Chemie
Y1  - 1973
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-57894
ER  - 
TY  - JOUR
A1  - Würthner, Frank
A1  - Noll, Niklas
T1  - A Calix[4]arene‐Based Cyclic Dinuclear Ruthenium Complex for Light‐Driven Catalytic Water Oxidation
JF  - Chemistry - A European Journal
N2  - A cyclic dinuclear ruthenium(bda) (bda: 2,2’‐bipyridine‐6,6’‐dicarboxylate) complex equipped with oligo(ethylene glycol)‐functionalized axial calix[4]arene ligands has been synthesized for homogenous catalytic water oxidation. This novel Ru(bda) macrocycle showed significantly increased catalytic activity in chemical and photocatalytic water oxidation compared to the archetype mononuclear reference [Ru(bda)(pic)\(_2\)]. Kinetic investigations, including kinetic isotope effect studies, disclosed a unimolecular water nucleophilic attack mechanism of this novel dinuclear water oxidation catalyst (WOC) under the involvement of the second coordination sphere. Photocatalytic water oxidation with this cyclic dinuclear Ru complex using [Ru(bpy)\(_3\)]Cl\(_2\) as a standard photosensitizer revealed a turnover frequency of 15.5 s\(^{−1}\) and a turnover number of 460. This so far highest photocatalytic performance reported for a Ru(bda) complex underlines the potential of this water‐soluble WOC for artificial photosynthesis.
KW  - water
KW  - oxidation
KW  - ruthenium
KW  - dinuclear
KW  - catalytic
KW  - artificial photosynthesis
KW  - homogenous catalysis
KW  - photocatalysis
KW  - ruthenium complexes
KW  - water oxidation
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230030
UR  - https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202004486
VL  - 27
IS  - 1
ER  - 
TY  - JOUR
A1  - Froudakis, G.
A1  - Zdetsis, A.
A1  - Mühlhäuser, M.
A1  - Engels, Bernd
A1  - Peyerimhoff, S. D.
T1  - A comparative ab initio study of the Si\(_2\)C\(_4\), Si\(_3\)C\(_3\), Si\(_4\)C\(_2\) clusters
N2  - Various structural possibilities for the Si\(_2\)C\(_4\) and Si\(_4\)C\(_2\) clusters are investigated by employing a basis set of triple-zeta plus polarization quality; electron correlation is generally accounted for by second-order M0ller-Plesset and, in certain instances, by higher-order perturbation (CASPT2) approaches. The building-up principle recently suggested from an analysis of Si\(_3\)C\(_3\) clusters is found to be fully operative for Si\(_2\)C\(_4\) and Si\(_4\)C\(_2\) clusters. A comparison of the structure and stability of various geometrical arrangements in the series C\(_6\) , Si\(_2\)C\(_4\) , Si\(_3\)C\(_3\) , Si\(_4\)C\(_2\), and Si\(_6\) shows that linear and planar structures become rapidly less stable if carbons are replaced by silicons and that the three-dimensional bipyramidal forms become less favorable as soon as silicons are exchanged by carbons in the parent Si\(_6\) structure. The effects can be rationalized in qualitative terms based on differences in silicon and carbon bonding.
KW  - Organische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59097
ER  - 
TY  - JOUR
A1  - Karak, Suvendu
A1  - Stepanenko, Vladimir
A1  - Addicoat, Matthew A.
A1  - Keßler, Philipp
A1  - Moser, Simon
A1  - Beuerle, Florian
A1  - Würthner, Frank
T1  - A Covalent Organic Framework for Cooperative Water Oxidation
JF  - Journal of the American Chemical Society
N2  - The future of water-derived hydrogen as the “sustainable energy source” straightaway bets on the success of the sluggish oxygen-generating half-reaction. The endeavor to emulate the natural photosystem II for efficient water oxidation has been extended across the spectrum of organic and inorganic combinations. However, the achievement has so far been restricted to homogeneous catalysts rather than their pristine heterogeneous forms. The poor structural understanding and control over the mechanistic pathway often impede the overall development. Herein, we have synthesized a highly crystalline covalent organic framework (COF) for chemical and photochemical water oxidation. The interpenetrated structure assures the catalyst stability, as the catalyst’s performance remains unaltered after several cycles. This COF exhibits the highest ever accomplished catalytic activity for such an organometallic crystalline solid-state material where the rate of oxygen evolution is as high as ∼26,000 μmol L\(^{–1}\) s\(^{–1}\) (second-order rate constant k ≈ 1650 μmol L s\(^{–1}\) g\(^{–2}\)). The catalyst also proves its exceptional activity (k ≈ 1600 μmol L s\(^{–1}\) g\(^{–2}\)) during light-driven water oxidation under very dilute conditions. The cooperative interaction between metal centers in the crystalline network offers 20–30-fold superior activity during chemical as well as photocatalytic water oxidation as compared to its amorphous polymeric counterpart.
KW  - water oxidation
KW  - sustainable energy source
KW  - covalent organic framework
KW  - catalyst
KW  - crystalline
KW  - catalysis
KW  - nanoparticles
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287591
UR  - https://pubs.acs.org/doi/10.1021/jacs.2c07282
SN  - 0002-7863
VL  - 144
IS  - 38
ER  - 
TY  - THES
A1  - Rehm, Thomas Helge
T1  - A Guide to Supramolecular Assemblies in Polar Solutions - From Nanometre-Sized Cyclic Dimers to Large Vesicular Structures
T1  - Ein Leitfaden für supramolekulare Verbände in polaren Lösungen - Von Nanometer-großen zyklischen Dimeren zu großen vesikularen Strukturen
N2  - This PhD thesis introduced several concepts for the construction of new supramolecular assem-blies in polar solvents. Although the building blocks differ in their binding mode and association strength they follow the same principle: one main driving force for the self-assembly in polar solutions in combination with one texturing force. The main self-assembly process is based on the mutual interaction of hydrogen-bond enforced ion pairs which deliver the association energy needed for stable, supramolecular structures even in polar solvents. The texturing force itself is represented by the linkers between the zwitterionic building blocks or parts of them. The different length and functionalization of the linkers have a tremendous influence on the mode of self-assembly leading to cyclic dimers, vesicles, layers or solid spheres. Hence, this principle is suitable for the construction of programmable monomers. Since the derivatisation of the main binding motive is rather simple it offers a great number of new and undoubtedly fascinating structures with potential applications in material and biomimetic science.
N2  - Diese Doktorarbeit stellte mehrere Konzept für den Aufbau von neuen supramolekularen Verbindungen in polaren Solventien vor. Obwohl sich die Bausteine bezüglich ihres Bindungsmodus und ihrer Assoziationsstärke unterscheiden, folgen sie alle dem gleichen Prinzip: eine Haupttriebkraft für den Selbstassoziationsprozess in polaren Lösemitteln in Kombination mit einer strukturgebenden Kraft. Die Haupttriebkraft stellen wasserstoffbrückenbindungsvermittelte Ionenpaare dar, die die nötige Assoziationsenergie für stabile, supramolekulare Strukturen auch in polaren Lösungen liefern. Die strukturierende Kraft selbst wird durch die Linkermoleküle zwi-schen den Zwitterionen oder Teilen von diesen vermittelt. Die unterschiedliche Länge und Funktionalisierung der Linker haben einen enormen Einfluss auf den Modus der Selbstassoziation, so dass die Bildung von zyklischen Dimeren, Vesikeln, Schichten oder Vollkugeln möglich war. Daher kann dieses Konzept für den Aufbau von programmierbaren Monomeren verwendet werden. Die Derivatisierung des zwitterionischen Bindungsmotivs gestaltet sich relativ einfach, so dass eine große Anzahl von neuen und zweifelsohne faszinierenden Nanostrukturen für zukünftige Anwendungen in der Materialwissenschaft und Biomimetik zur Verfügung steht.
KW  - Supramolekulare Chemie
KW  - Vesikel
KW  - Selbstassoziation
KW  - polare Lösung
KW  - vesicle
KW  - self-assembly
KW  - polar solution
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-28359
ER  - 
TY  - JOUR
A1  - Farrell, Jeffrey  M.
A1  - Grande, Vincenzo
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - A Highly Warped Heptagon-Containing sp\(^2\) Carbon Scaffold via Vinylnaphthyl π-Extension
JF  - Angewandte Chemie International Edition
N2  - 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.
KW  - arenes
KW  - carbon
KW  - C-C coupling
KW  - curvature
KW  - polycyclic aromatic hydrocarbons
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206682
VL  - 58
IS  - 46
ER  - 
TY  - JOUR
A1  - Schneider, Tilman
A1  - Seebauer, Florian
A1  - Beuerle, Florian
A1  - Würthner, Frank
T1  - A monodisperse, end‐capped Ru(bda) oligomer with outstanding performance in heterogeneous electrochemical water oxidation
JF  - Advanced Materials Technologies
N2  - AbstractWater oxidation catalysis is a key step for sustainable fuel production by water splitting into hydrogen and oxygen. The synthesis of a novel coordination oligomer based on four Ru(bda) (bda = 2,2′‐bipyridine‐6,6′‐dicarboxylate) centers, three 4,4′‐bipyridine (4,4′‐bpy) linkers, and two 4‐picoline (4‐pic) end caps is reported. The monodispersity of this tetranuclear compound is characterized by NMR techniques. Heterogeneous electrochemical water oxidation after immobilization on multi‐walled carbon nanotubes (MWCNTs) shows catalytic performance unprecedented for this compound class, with a turnover frequency (TOF) of 133 s\(^{−1}\) and a turnover number (TON) of 4.89 × 10\(^6\), at a current density of 43.8 mA cm\(^{−2}\) and a potential of 1.45 V versus normal hydrogen electrode (NHE).
KW  - water oxidation catalysis
KW  - coordination oligomers
KW  - electrocatalysis
KW  - heterogeneous catalysis
KW  - renew-able fuels
KW  - ruthenium bda complexes
KW  - water splitting
Y1  - 2024
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-363133
SN  - 2365-709X
VL  - 9
IS  - 11
ER  - 
TY  - INPR
A1  - Höbartner, Claudia
A1  - Steinmetzger, Christian
A1  - Palanisamy, Navaneethan
A1  - Gore, Kiran R.
T1  - A multicolor large Stokes shift fluorogen-activating RNA aptamer with cationic chromophores
T2  - Chemistry - A European Journal
N2  - Large Stokes shift (LSS) fluorescent proteins (FPs) exploit excited state proton transfer pathways to enable fluorescence emission from the phenolate intermediate of their internal 4 hydroxybenzylidene imidazolone (HBI) chromophore. An RNA aptamer named Chili mimics LSS FPs by inducing highly Stokes-shifted emission from several new green and red HBI analogs that are non-fluorescent when free in solution. The ligands are bound by the RNA in their protonated phenol form and feature a cationic aromatic side chain for increased RNA affinity and reduced magnesium dependence. In combination with oxidative functional-ization at the C2 position of the imidazolone, this strategy yielded DMHBO\(^+\), which binds to the Chili aptamer with a low-nanomolar K\(_D\). Because of its highly red-shifted fluorescence emission at 592 nm, the Chili–DMHBO\(^+\) complex is an ideal fluorescence donor for Förster resonance energy transfer (FRET) to the rhodamine dye Atto 590 and will therefore find applications in FRET-based analytical RNA systems.
KW  - RNA Aptamer
KW  - fluorescence
KW  - large Stokes shift
KW  - fluorescent protein
KW  - fluorescent resonance energy transfer
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-174197
N1  - This is the pre-peer reviewed version of the following article: Steinmetzger, C. , Palanisamy, N. , Gore, K. . and Höbartner, C. (2018), A multicolor large Stokes shift fluorogen‐activating RNA aptamer with cationic chromophores. Chem. Eur. J. doi:10.1002/chem.201805882, which has been published in final form at https://doi.org/10.1002/chem.201805882. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
ER  - 
TY  - JOUR
A1  - Suter, H. U.
A1  - Huang, M.-B.
A1  - Engels, Bernd
T1  - A Multireference Configuration Interaction Study of the Hyperfine Structure of the Molecules CCO, CNN and NCN in their triplet ground states
N2  - The hyperfine structures of the isoelectronic molecules CCO. CNN, and NCN in their triplet ground states (X\(^3 \sum ^-\)) are investigated by means of ab initio methods. The infrared frequencies and geometries are detennined and compared with experiment. Configuration selected multireference configuration interaction calculations in combination with perturbation theory to correct the wave function (MRD-CI/B\(_K\)) employing extended atomic orbital (AO) basis sets yielded very accurate hyperfine properties. The theoretical values for CCO are in excellent agreement with the experimental values determined by Smith and Weltner [J. Chem. Phys. 62,4592 (1975)]. For CNN, the first assignment of Smith and Weltner for the two nitrogen atoms has to be changed. A qualitative discussion of the electronic structure discloses no simple relation between the structure of the singly occupied orbitals and the measured hyperfine coupling constants. Vibrational effects were found to be of little importance.
KW  - Organische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59108
ER  - 
TY  - JOUR
A1  - Solger, Franziska
A1  - Kunz, Tobias C.
A1  - Fink, Julian
A1  - Paprotka, Kerstin
A1  - Pfister, Pauline
A1  - Hagen, Franziska
A1  - Schumacher, Fabian
A1  - Kleuser, Burkhard
A1  - Seibel, Jürgen
A1  - Rudel, Thomas
T1  - A Role of Sphingosine in the Intracellular Survival of Neisseria gonorrhoeae
JF  - Frontiers in Cellular and Infection Microbiology
N2  - Obligate human pathogenic Neisseria gonorrhoeae are the second most frequent bacterial cause of sexually transmitted diseases. These bacteria invade different mucosal tissues and occasionally disseminate into the bloodstream. Invasion into epithelial cells requires the activation of host cell receptors by the formation of ceramide-rich platforms. Here, we investigated the role of sphingosine in the invasion and intracellular survival of gonococci. Sphingosine exhibited an anti-gonococcal activity in vitro. We used specific sphingosine analogs and click chemistry to visualize sphingosine in infected cells. Sphingosine localized to the membrane of intracellular gonococci. Inhibitor studies and the application of a sphingosine derivative indicated that increased sphingosine levels reduced the intracellular survival of gonococci. We demonstrate here, that sphingosine can target intracellular bacteria and may therefore exert a direct bactericidal effect inside cells.
KW  - sphingosine
KW  - sphingolipids
KW  - sphingosine kinases
KW  - invasion
KW  - survival
KW  - click chemistry
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204111
SN  - 2235-2988
VL  - 10
ER  - 
TY  - JOUR
A1  - Okuda, Takumi
A1  - Lenz, Ann-Kathrin
A1  - Seitz, Florian
A1  - Vogel, Jörg
A1  - Höbartner, Claudia
T1  - A SAM analogue-utilizing ribozyme for site-specific RNA alkylation in living cells
JF  - Nature Chemistry
N2  - Post-transcriptional RNA modification methods are in high demand for site-specific RNA labelling and analysis of RNA functions. In vitro-selected ribozymes are attractive tools for RNA research and have the potential to overcome some of the limitations of chemoenzymatic approaches with repurposed methyltransferases. Here we report an alkyltransferase ribozyme that uses a synthetic, stabilized S-adenosylmethionine (SAM) analogue and catalyses the transfer of a propargyl group to a specific adenosine in the target RNA. Almost quantitative conversion was achieved within 1 h under a wide range of reaction conditions in vitro, including physiological magnesium ion concentrations. A genetically encoded version of the SAM analogue-utilizing ribozyme (SAMURI) was expressed in HEK293T cells, and intracellular propargylation of the target adenosine was confirmed by specific fluorescent labelling. SAMURI is a general tool for the site-specific installation of the smallest tag for azide-alkyne click chemistry, which can be further functionalized with fluorophores, affinity tags or other functional probes.
KW  - Alkyltransferase Ribozyme SAMURI
KW  - Site-specific RNA labelling
KW  - bioorthogonal SAM analogue ProSeDMA
KW  - Chemical modification
KW  - RNA
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-328762
ER  - 
TY  - INPR
A1  - Neitz, Hermann
A1  - Höbartner, Claudia
T1  - A tolane-modified 5-ethynyluridine as a universal and fluorogenic photochemical DNA crosslinker
T2  - Chemical Communications
N2  - We report the fluorescent nucleoside ToldU and its application as a photoresponsive crosslinker in three different DNA architectures with enhanced fluorescence emission of the crosslinked products. The fluorogenic ToldU crosslinking reaction enables the assembly of DNA polymers in a hybridization chain reaction for the concentration-dependent detectio of a specific DNA sequence.
KW  - Tolane-Modified Fluorescent Nucleosides
KW  - Photoresponsive DNA Crosslinker
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-328255
ET  - submitted version
ER  - 
TY  - JOUR
A1  - Kirchner, Philipp H.
A1  - Schramm, Louis
A1  - Ivanova, Svetlana
A1  - Shoyama, Kazutaka
A1  - Würthner, Frank
A1  - Beuerle, Florian
T1  - A water-stable boronate ester cage
JF  - Journal of the American Chemical Society
N2  - The reversible condensation of catechols and boronic acids to boronate esters is a paradigm reaction in dynamic covalent chemistry. However, facile backward hydrolysis is detrimental for stability and has so far prevented applications for boronate-based materials. Here, we introduce cubic boronate ester cages 6 derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding, dynamic exchange at the Lewis acidic boron sites is feasible only under acid or base catalysis but fully prevented at neutral conditions. For the first time, boronate ester cages 6 tolerate substantial amounts of water or alcohols both in solution and solid state. The unprecedented applicability of these materials under ambient and aqueous conditions is showcased by efficient encapsulation and on-demand release of β-carotene dyes and heterogeneous water oxidation catalysis after the encapsulation of ruthenium catalysts.
KW  - absorption
KW  - hydrocarbons
KW  - materials
KW  - organic compounds
KW  - stability
KW  - boronate esters
Y1  - 2024
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-361245
SN  - 0002-7863
VL  - 146
IS  - 8
ER  - 
TY  - JOUR
A1  - Peric, M.
A1  - Engels, Bernd
T1  - Ab initio calculation of the vibronically averaged hyperfine coupling constants in the 1\(^2\)Π\(_u\) electronic state of CH\(_2 ^+\)
N2  - The results of pure ab initio calculations of the hyperfine coupling constants for the 1 \(^2 \pi _u\) electronic state for various isotopomers of CHi in the energy range between 0 and 20 000 cm\(^{-1}\) are presented. Effects of vibronic and spin-orbit coupling are discussed.
KW  - Organische Chemie
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58951
ER  - 
TY  - JOUR
A1  - Staikova, M.
A1  - Engels, Bernd
A1  - Peric, M.
A1  - Peyerimhoff, S. D.
T1  - Ab initio calculation of the vibronically averaged hyperfine coupling constants in the two lowest electronic states of H\(_2\)O\(^+\)
N2  - No abstract available
T2  - Ab initio calculations of the vibronically averaged hyperfine coupling constants in the 1\(^2\)Π\(_u\)(X\(^2\)B\(_1\),A\(^2\)A\(_1\)) state of the water cation
KW  - Organische Chemie
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58998
ER  - 
TY  - JOUR
A1  - Peric, M.
A1  - Engels, Bernd
T1  - Ab initio calculations of the vibronically averaged values for the hyperfine coupling constants in NH\(_2\), NHD and ND\(_2\)
N2  - Vibronically averaged values for K =0 and K = 1 bending levels in the energy range between 0 and 25 000 cm\(^{-1}\) are computed for the \(^{14}\)N, H, and D atoms in NH\(_2\), NHD, and ND\(_2\) The pure ab initio electronic potentials, as well as those derived by fitting of experimentally observed band positions are employed. Effects of vibronic coupling and local perturbations of close-lying levels belanging to different electronic states are discussed.
KW  - Organische Chemie
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58941
ER  - 
TY  - JOUR
A1  - Karna, S.P.
A1  - Grein, F.
A1  - Engels, Bernd
A1  - Peyerimhoff, S.D.
T1  - Ab initio configuration-interaction studies of the ground state potential energy and hyperfine coupling constants of \(^{35}\)Cl\(_2^-\)
N2  - Potential energy and spectroscopic constants for the X\(^2 \sum^+ _\mu\) ground state of a;, were calculated by configuration-interaction (Cl) methods, using large basis sets with polarization and diffuse functions. From these CI wavefunctions, the isotropic (a\(_{iso}\)) and dipolar (A\(_{dip}\)) components of the hyperfine coupling constant were obtained. The effects of various s, p basis sets, polarization and diffuse functions, as well as the influence of reference configurations and configuration selection thresholds were investigated. The best values obtained are 35·31 G for a\(_{iso}\) and 29·440 for A\(_{dip}\)• tobe compared with experimental values of 37 ± 1 G and 32 ± 1 G, respectively. It is shown that the contributions to a1so of the K and L shells are opposite in sign, differing by about 4 G. Upon vibrational averaging, both a\(_{iso}\) and A\(_{dip}\) move towards smaller values as v increases. An adiabatic electron affinity of 2·46eV was obtained for CL\(_2\) , and a vertical electron detachment energy of 3·71 eV for Cl;.
KW  - Organische Chemie
Y1  - 1990
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58869
ER  - 
TY  - JOUR
A1  - Staikova, M.
A1  - Engels, Bernd
A1  - Peric, M.
T1  - Ab initio investigation of the hyperfine structure in the 1\(^2\)Π\(_u\)(X\(^2\)A\(_1\), A\(^2\)B\(_1\) system of BH\(_2\))
N2  - No abstract available
KW  - Organische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59000
ER  - 
TY  - JOUR
A1  - Mühlhäuser, M.
A1  - Froudakis, G.
A1  - Zdetsis, A.
A1  - Engels, Bernd
A1  - Flytzanis, N.
A1  - Peyerimhoff, S. D.
T1  - Ab initio investigation of the stability of Si\(_3\)C<\(_3\) clusters and their structural and bonding features
N2  - Various structural possibilities for Si\(_3\)C\(_3\) clusters are investigated by ab initio calculations employing basis sets of double- and triple-zeta quality augmented by d polarization functions. Correlation effects are included by a second-order Moeller Piesset perturbation treatment. For the two lowest-lying structures higher-order correlation corrections and multi-reference effects are also included. Bonding features are investigated by two different types of population analyses to obtain insight into the nature of chemical bonding. A total of 17 stationary points were investigated, 14 of which correspond to local minima and three being transition states. The energetically lowest-lying structures are: A "pyramidlike" structure with various multicenter bonds, followed by a es symmetric isomer closely related to the ground state Si6 structure. Planar structures, favoured in small carbon clusters, lie higher in energy and are transition states. The lowest-lying triplet system is found to be the linear nonsymmetric Si - C-C-C-Si -Si structure, which is calculated to lie about 38 kcalfmole above the singlet ground state. A building-up principle based on bonding criteria is suggested for the occurence of the various structural possibilities.
KW  - Organische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59060
ER  - 
TY  - JOUR
A1  - Staikova, M.
A1  - Peric, M.
A1  - Engels, Bernd
A1  - Peyerimhoff, S. D.
T1  - Ab initio Investigation of the Structure of the X\(^2\)A', A\(^2\)A'' (1\(^2\)Π) Spectral System of HCO: Investigation of the Magnetic Hyperfine Effects
N2  - Results ofan ab initio study ofthe hyperfine structure of the X\(^2\)A', A\(^2\) A" ( 1\(^2 \Pi\)) system ofthe formyl radical are presented. Special attention is paid to the analysis of the interplay between the vibronic and magnetic hyperfine etfects. The results of computations are in very good agreement with the available experimental findings. The values for the hyperfine coupling constants in lower bending Ievels of both electronic species are predicted.
KW  - Organische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59089
ER  - 
TY  - JOUR
A1  - Peric, M.
A1  - Engels, Bernd
A1  - Peyerimhoff, S.D.
T1  - Ab initio investigation of the vibronic structure of the C\(_2\)H spectrum Calculation of the hyperfine coupling constants for the three lowest lying electronic states
N2  - The hyperfine coupling constants (isotropic hfcc and four Cartesian components of the ani~ tropic tensor) are calculated for all three atoms of C\(_2\)H in its three lowest-lying electronic states at various molecu)ar geometries by means of the ab initio configuration interaction ( MRO.CI) method. The off-diagonal electronic matrix elements involving the two species ofthe A' symmetry are also computed. A diabatic transforrnation is perforrned Jeading to simple geometrical depen· dences of the hyperline coupling constants.
KW  - Organische Chemie
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58901
ER  - 
TY  - JOUR
A1  - Peric, M.
A1  - Engels, Bernd
A1  - Peyerimhoff, S.D.
T1  - Ab initio investigation of the vibronic structure of the C\(_2\)H spectrum Computation of the vibronically-averaged values for the Hyperfine Coupling Constants
N2  - The vibronically averaged values for tbe hyperfine coupling constants in the X\(^2 \sum\)-A\(^2 \Pi\) system of the ethynyl radical are computed by means of tbe ab initio metbod calculations. The results point at tbe importance of taking into account the coupling of a1l tbree electronic states in question ( I\(^2\)A', 2\(^2\)A', and 1\(^2\)A") for a reliable explanation of the available experimental findings. The mean values of the hfcc's for K = 0 and 1 levels in \(^{13}\)C\(_2\)H and \(^{13}\)C\(_2\)D in the energy range up to 6000 cm\(^{-1}\) are predicted.
KW  - Organische Chemie
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58915
ER  - 
TY  - JOUR
A1  - Pleß, V.
A1  - Suter, H. U.
A1  - Engels, Bernd
T1  - Ab initio study of the energy difference between the benzene and the cumulene form of the C\(_6\) molecule
N2  - The energy difference between the three lowest-lying isomers of C\(_6\) the linear \(^3 \sum ^-\) state and the two ring forms,the benzene structure (\(^1\)A\(_{18}\)) possessing D\(_{6h}\) symmetry and a distorted cyclic form ( \(^1\)A'\(_1\), D\(_{3h}\) symmetry) have been calculated using various ab initio methods. Variational methods such as multireference configuration interaction (MR-CI) and complete active space second order perturbatiOn treatment (CASPT2) have been applied, as weil as perturbational treatments and coupled cluster calculations (CCD). The correlation of all valence shell electrons is found to be important for a balanced description of the isomers of C\(_6\) . Methods which do not account for higher-order effects appropriately proved to be unsuitable for calculating the energy difference correctly. The results from multireference configuration interaction methods show that the isomers are close in energy with the cyclic forms somewhat lower than the linear form. The ring form possessing D\(_{3h}\) symmetry (\(^1\)A'\(_1\)} is found tobe the lowest-lying structure.
KW  - Organische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59059
ER  - 
TY  - THES
A1  - Hupp, Thomas
T1  - Ab Initio Treatment of Complex Systems Kohn-Sham Orbitals for Multi Reference Methods and the Base Pairing Properties of Xanthine
T1  - Ab initio Behandlung komplexer Systeme Kohn-Sham Orbitale für Multireferenzverfahren und die Basenpaarungseigenschaften von Xanthin
N2  - Die vorliegende Arbeit besteht aus zwei Teilen. Der erste untersucht die Eignung von LHF-Orbitalen für Multireferenzverfahren. Das Ziel dieses Teils ist eine effizientere Berechnung angeregter Zustände, was zur spektroskopischen Charakterisierung vieler organischer und bioorganischer Moleküle wichtig ist. Der zweite Teil befasst sich mit bioorganischen Fragestellungen und untersucht die Paarungseigenschaften der Purinbase Xanthin. Es wird unter anderem die unerwartet hohe Stabilität der Xanthin Selbstpaarung in Alanyl-PNA erklärt und es wird untersucht, auf welche Weise Xanthin in der DNA mutagene Fehlpaarungen mit Thymin eingehen kann. Teil1: Im Unterschied zu HF- und Standard-DFT-Methoden führt der LHF-Ansatz zu einem vollständig gebundenen Orbitalspektrum, da Coulomb-Selbstwechselwirkungen im LHF-Ansatz exakt korrigiert werden. Durch die Korrektur der Coulomb-Selbstwechselwirkungen sind im LHF-Ansatz auch die Energien der besetzten Orbitale nicht wie in Standard-DFT-Methoden zu höheren Werten verschoben, so dass das Koopmans' Theorem gültig bleibt und die besetzten LHF-Orbitale etwas kompakter als Standard-DFT-Orbitale sind. Die vorliegende Arbeit zeigt, dass beide Eigenschaften deutliche Vorteile für MR-Verfahren darstellen. Die virtuellen LHF-Orbitale sind gut optimiert und erlauben eine effizienteBeschreibung sowohl angeregter Zustände als auch statischer Korrelationseffekte in MRCI und MRPT2-Ansätzen. Weiterhin führt die kompaktere Struktur der besetzten LHF-Orbitale zu einer besseren Beschreibung des kationischen Rumpfes von Rydbergzuständen. Andererseits wurden zu beiden genannten Vorteilen auch jeweils ein Beispielmolekül gefunden, in dem die Vorteile nicht zum Tragen kommen, und zu deren Beschreibung Orbitale aus HF- oder Standard-DFT-Methoden besser geeignet sind. Diese Beispiele zeigen, dass jeder Einzelfall für sich getestet werden muss, auch wenn die angeregten Zustände der meisten Moleküle sehr gut mit LHF-Orbitalen beschrieben werden können. Teil 2: Im zweiten Teil der vorliegenden Arbeit wurden die Paarungseigenschaften von Xanthin und Xanthinderivaten untersucht. Ziel dieses Teils war es, eine Erklärung für die unerwartet hohe Stabilität des Xanthin Alanyl-PNA Selbstpaarung zu finden. Weiterhin wurde untersucht, weshalb Xanthin, das in der DNA u.a. unter chemischem Stress gebildet wird, mutagene Fehlpaarungen mit der Pyrimidinbase Thymin eingehen kann. Stabilität der Xanthin Alanyl PNA: Zunächst wurde durch den Vergleich experimenteller und berechneter 13C-NMR-Spektra das Regiosomer von Xanthin bestimmt, welches zu der ungewöhnlich hohen Stabilität der Xanthin-Xanthin-Selbstpaarung in Alanyl-PNA verantwortlich ist. Zur Untersuchung der Stabilität der Xanthin-Selbstpaarung wurde ein stark vereinfachendes Modell aufgestellt,in dem die Stabilit� at der PNA-Duplexe nur über die Energiebeiträge aus den Wasserstoffbrücken (EDim) und der Basenstapelung (EStap) bestimmt wird. Die Dimerisierungs- und Stapelungsenergien unterschiedlicher Paarungen wurden mit DFT- und MP2-Methoden bestimmt. Solvenseffekte wurden über ein Kontinuummodell erfasst und der Einfluss des peptidischen Rückgrats auf die Stapelungsgeometrie wurde durch Kraftfeldmethoden berücksichtigt. Während die einzelnen Energiekomponenten aus den H-Br� ucken und der Basenstapelung keinen eindeutigen Zusammenhang zu den Schmelztemperaturen erkennen lassen, korreliert die Summe aus beiden linear mit den experimentell ermittelten Tm-Werten. Dies bedeutet, dass die Beiträge aus der Entropie, der molekularen Wasserumgebung und der Rückgratspannung sich entweder aufheben oder f� ur alle behandelten Systeme sehr ähnlich sind. Die Stabilität der Xanthin-Xanthin- und die der 2,6-Diaminopurin-Xanthin-Paarung, ergibt sich durch einen erhöhten Stapelungsbeitrag der Purinpaarungen, während die Wasserstoffbrücken der Xanthin Selbstpaarung nur wenig zur Stabilisierung des Xanthin-Xanthin und des Xanthin-Diaminopurin-Alanyl-PNA-Doppelstrangs beitragen. Paarungseigenschaften von N9-Xanthin: Zur Untersuchung der Paarungseigenschaften von N9-Xanthin wurden zun� achst H-verbrückte Homodimere von Xanthin untersucht. Hierbei wurden extreme Variationen in den Bindungsstärken der einzelnen H-Brücken gefunden, die sich zwischen -4 bis -11 kcal/mol in der Gasphase und -2.5 bis -5 kcal/mol im Solvens betragen. Durch Vergleich mit Modellsystemen konnte die starke Varianz der H-Brückenstärke auf anziehende bzw. abstoßende sekundäre elektrostatische Wechselwirkungen zurückgeführt werden. Weiterhin wurde das Homodimer von Hypoxanthin untersucht, bei dem die H-Brücken durch eine Erhöhung der Aromatizität im Pyrimidinring zusätzlich verstärkt werden, was zu einer deutlichen Stabilisierung des Dimers führt. Elektronische Effekte müssen vor allem deshalb berücksichtigt werden, da sie im Unterschied zu rein elektrostatischen Effekten deutlich weniger von der Solvensumgebung beein usst werden. Mutagenität von Hypoxanthin und Xanthin: Zur Erklärung der Mutagenität von Hypoxanthin und Xanthin wurden verschiedene neutrale und anionische Watson-Crick Basenpaarungen von Hypoxanthin und Xanthin mit Pyrimidinbasen berechnet. Hierbei wurden u. a. auch tautomere und anionische Formen von Xanthin berücksichtigt. Zur Bewertung der erhaltenen Dimerisierungsenergien wurden die Paarungen danach klassifiziert, ob ihre Geometrien mit denen der kanonischen Basenpaarungen deckungsgleich sind, oder ob sie in einer verzerrten Watson-Crick Geometrie vorliegen, was die Einbaurate in die DNA aufgrund des räumlichen Anspruchs der DNA-Polymerase vermindert. Die Rechnungen zeigen, dass Xanthin nur mit Cytosin Watson-Crick-Paarungen eingehen kann, welche jedoch nur sehr schwach gebunden sind. In der neutralen Form scheint eine dreizähnige Basenpaarung unter Beteiligung einer tautomeren Form des Xanthins etwas stabiler zu sein als die zweizähnige Paarung von Diketoxanthin mit Cytosin. Da die Dimerisierungsenergie sowohl der neutralen als auch der anionischen Basenpaarung nur wenig unter 0 kcal/mol liegt, ist der Einbau der Xanthin-Cytosin-Paarung in die DNA zwar aufgrund der günstigen Geometrie möglich, wird aber nicht durch einen Energiebeitrag aus den H-Brücken verstärkt. Die im Vergleich zur Guanin-Cytosin Paarung deutlich geringere Aromatizität von Xanthin zu Cytosin ist im Einklang mit dem experimentellen Befund, dass die Cytosin-Xanthin Paarung deulich langsamer als die Guanin-Cytosin Paarungen in die DNA eingebaut werden. Während die Rechnungen nur eine geringe Aromatizität von Xanthin zu Cytosin vorhersagen, scheint das Anion von Xanthin in der Lage zu sein, eine sehr stabile Basenpaarung mit Thymin einzugehen. Allerdings muss die Dimerisierungsenergie die schlechtere Anpassung in die Bindungstasche der DNA-Polymerase ausgleichen, da die Paarung in einer etwas verzerrten Watson-Crick Geometrie vorliegt. Insgesamt wird die Paarung daher nicht schneller in die DNA eingebaut, wie erwartet aufgrund der H-Brückenstärken, stattdessen besitzt sie eine ähnliche Einbaurate wie die geometrisch günstigere aber weniger stabile Xanthin-Cytosin Paarung.
N2  - The present work consists of two parts. The first one deals with theoretical questions and tests the performance of orbitals obtained from a self-interaction free KS method, the LHFapproach, in multireference ab initio methods. The purpose of this part is to enable a more efficient computation of excitation energies, which is important for the spectroscopic characterization of many organic and bioorganic molecules. The second part focuses on bioorganic questions and studies the base pairing properties of the purine base xanthine in order to explain, e.g., the unusually high stability of selfpairing xanthine alanyl-PNA double strands and the mutagenicity of xanthine formed in DNA. Part1: In contrast to HF- and standard DFT-methods, the LHF-approach leads to a fully bound virtual orbital spectrum, because Coulomb self interactions are exactly canceled in the LHFansatz. Furthermore, the energies of the occupied orbitals are not upshifted, like it is the case for standard DFT-methods, so that Koopmans' theorem remains valid. In line with this, also the occupied LHF-orbitals are somewhat more compact than standard DFT-orbitals. The present work shows that both properties are of great benefit for MR methods. The virtual LHF-orbitals are well optimized and allow an efficient description of excited states and static correlation in both MRCI- and MRPT2-approaches. Furthermore, the higher compactness of the occupied LHF- compared to standard DFT-orbitals leads to a better description of the center ion of Rydberg states. However, for each of the two advantages mentioned at least one example molecule has been found, for which LHF-orbitals actually perform worse than HF-and/or standard DFT-orbitals. This shows, that even though LHF virtual orbitals allow an excellent MRCI- and MRPT2-description for the electronically excited states of a large number of molecules, this cannot be generalized and their performance needs to be tested for each individual case. In the second part of the present work, the base pairing properties of xanthine and xanthine derivatives were studied. The purpose of this part was to find an explanation for the unexpectedly high stability of the xanthine alanyl PNA double strand. Furthermore, it was analyzed, why xanthine, that is formed from guanine in DNA under chemical stress, is able to form mismatched base pairs with the pyrimidine base thymine. Stability of xanthine alanyl PNA: In the first step, the regioisomer present in the considered alanyl PNA was identified to be the N7-regioisomer of xanthine by a theoretical analysis of the 13C-NMR spectrum. To analyze the stability of the xanthine self-pairing, a simplified model was set up, in which the stability of the PNA double strand was explained solely by the energy contributions from H-bonding and base stacking. For that purpose, the dimerization and stacking energies for the xanthine-xanthine, guaninecytosine, adenine-thymine and xanthine-2,6-diaminopurine base pairs were computed using DFT and MP2 methods. Solvent effects were taken into account by the conductor like screening model. The influence of the peptide backbone on the stacking geometry was considered by force field optimizations. While the individual contributions from hydrogen bonding and stacking do not correlate with the melting temperature Tm, the sum of both correlates linearly with Tm. This correlation is somewhat surprising, because this means that the effects of the entropy and the molecular water environment either cancel or are similar for all systems compared. In this model, the stability of the xanthine selfpairing mainly stems from an enlarged stacking interaction, while the H-bonds give only minor contributions to the stability of the xanthine selfpaired double strand of alanyl-PNA. Base pairing properties of N9-Xanthine: The computation of the base pairing properties of N9-xanthine revealed a strong variation in the individual H-bond strengths for the selfpairing of xanthine, that range from -4 to -11 kcal/mol in the gas phase and -2.5 to -5 kcal/mol in polar solvent. By comparison with model systems it was shown that the strong variance of the H-bond strength is mainly due to attractive or repulsive secondary electrostatic interactions. For the homodimer of hypoxanthine it was shown that the increase of aromaticity in the pyrimidine ring upon dimer formation leads to a strengthening of the hydrogen bonds. Mutagenicity of hypoxanthine and xanthine: Several neutral and anionic Watson-Crick base pairs of xanthine were computed with MP2- and DFT-methods in order to explain the mutagenicity of hypoxanthine and xanthine. Also basepairs involving tautomeric forms of xanthine and hypoxanthine were considered. To evaluate the dimerization energies found, the dimers were classified into pairings that have the exact geometry of the canonical base pairs and those that realize a distorted Watson-Crick pairing mode. The computations show that a stable pairing which realizes the exact geometry of a canonical Watson Crick base pairing is only possible for the pairing of xanthine to cytosine, however, the base pairs are only weakly bound. The dimerization energies of both the neutral and the anionic pairing is around 0 kcal/mol, so that the xanthine-cytosine base pairs are incorporated into DNA solely because the base pairs fulfill the geometric demands of DNA polymerase, but it does not profit from any additional stabilization due to hydrogen bonding. The bonding that in the Watson-Crick pairing mode xanthine has almost no affinity to cytosine is in correspondence with the experimental result that the cytosine-xanthine base pair is incorporated into DNA at a much lower rate than the cytosine-guanine base pair, which has a very strong hydrogen bonding. While the affinity of xanthine to cytosine is very low, the computations predict that xanthine is able to form a stable Watson-Crick pairing with thymine. However, the pairing has a somewhat distorted Watson-Crick geometry, so that its high stability is outbalanced by the worsened fit to the binding pocket of DNA-polymerase. As a consequence, the xanthinethymine pairing is incorporated into DNA not at a faster, but only at a rate comparable to that of the xanthine-cytosine pairing.
KW  - Kohn-Sham Orbitale
KW  - MRCI
KW  - angeregte Zustände
KW  - Basenpaarung
KW  - Xanthin
KW  - Kohn-Sham Orbitals
KW  - MRCI
KW  - excited states
KW  - Base pairing
KW  - xanthine
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-8244
ER  - 
TY  - THES
A1  - Maksimenka, Katsiaryna
T1  - Absolute Configuration by Circular Dichroism: Quantum Chemical CD Calculations
T1  - Absolute Konfiguration durch Circular-Dichroismus: Quantenchemische Rechnungen des Circular-Dichroismus (CD)
N2  - Quantum chemical calculations of circular dichroism (CD) spectra in combination with experimental CD studies are one of the most efficient analytical tools for the elucidation of the three-dimensional structure of a chiral molecule. In the present work 18 chiral compounds of most different molecular structures and origins were investigated using various theoretical methods (the semiempirical CIS methods, the time-dependent DFT and DFT/MRCI approaches). The advantages and limitations of the applied methods were discussed in the context of the studied compounds. Furthermore, the last part of this work deals with the CD investigations of a chiral compound in the crystalline state. A well-known natural product with a specific conformation/CD spectrum behavior was used as a model compound to examine a novel solid-state CD method and to investigate the possibility of its improvement to provide a higher reliability for the assignment of the absolute configuration.
N2  - Quantenchemische Rechnungen des Circular-Dichroismus (CD) in Kombination mit experimentellen CD-Studien sind eines der besten analytischen Werkzeuge zur Aufklärung der dreidimensionalen Struktur eines chiralen Moleküls. In der vorliegenden Arbeit wurden 18 chirale Verbindungen mit unterschiedlichsten Strukturen und von unterschiedlichster Herkunft unter Verwendung von verschiedenen theoretischen Methoden (semiempirische CIS-Methoden, zeitabhängige DFT- und DFT/MRCI-Ansätze) untersucht. Die Vorteile und Grenzen der angewandten Methoden wurden im Rahmen der untersuchten Verbindungen diskutiert. Desweiteren befasst sich der letzte Teil der vorliegenden Arbeit mit den CD-Untersuchungen einer chiralen Verbindung im kristallinen Zustand. Ein bekannter Naturstoff mit einem spezifischen Konformation/CD-Spektrum-Verhalten wurde als Modellverbindung verwendet, um einen neuartige Festkörper-CD-Ansatz zu testen, und um die Möglichkeit seiner Verbesserung zu untersuchen, um eine höhere Zuverlässlichkeit für die Zuordnung der absoluten Konfiguration zu bieten.
KW  - Circular-Dichroismus
KW  - Quantenchemie
KW  - Konfiguration <Chemie>
KW  - Quantenchemische Rechnungen
KW  - Absolute Konfiguration
KW  - Absolute Configuration
KW  - Circular Dichroism
KW  - Quantum Chemical CD Calculations
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-56552
ER  - 
TY  - JOUR
A1  - Sun, Meng‐Jia
A1  - Anhalt, Olga
A1  - Sárosi, Menyhárt B.
A1  - Stolte, Matthias
A1  - Würthner, Frank
T1  - Activating Organic Phosphorescence via Heavy Metal–π Interaction Induced Intersystem Crossing
JF  - Advanced Materials
N2  - Heavy‐atom‐containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface‐bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid‐state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)\(_{2}\)) as a triplet sensitizer and electron‐deficient 1,4,5,8‐naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room‐temperature phosphorescence confined in the low‐lying, long‐lived triplet state of NDIs with photoluminescence (PL) quantum yield (Φ\(_{PL}\)) exceeding 25% and a phosphorescence lifetime (τ\(_{Ph}\)) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin–orbital coupling between the constituents.
KW  - cocrystallization
KW  - naphthalene diimide
KW  - phosphorescence
KW  - platinum complexes
KW  - triplet sensitization
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312248
VL  - 34
IS  - 51
ER  - 
TY  - THES
A1  - Renner, Rebecca
T1  - Aggregation, Chirality and Reduction of Nonplanar Polycyclic Aromatic Hydrocarbons
T1  - Aggregation, Chiralität und Reduktion Nichtplanarer Polyzyklischer Aromatischer Kohlenwasserstoffe
N2  - Within this thesis the interactions between novel corannulene derivatives in solution as well as in the solid state by changing the imide residue of a literature known extended corannulene dicarboximide were investigated, in order to obtain a better understanding of the packing and possible charge transport in potential applications. Accordingly, the goal of the work was to synthesize and investigate an electron-poor corannulene bis(dicarboximide) based on previously published work but with higher solubility and less steric encumbrance in imide position to enable self-assembly in solution.
To obtain further insights into the conformational stability, structure and chiroptical properties of heavily twisted PBIs another aim of this thesis was the design, synthesis, and optoelectronic investigation of various fourfold directly arylated PBIs  by substitution in bay position with smaller hydrocarbons with different steric demand, i.e., benzene, naphthalene and pyrene, which should be separable by chiral high performance liquid chromatography (HPLC).
As of yet, no concise study concerning the optical and electronic properties of differently core-substituted PBIs in the neutral as well as the mono- and dianionic state in solution is available, which also elucidates the origin of the different optical transitions observed in the absorption and emission spectra. Thus, in this thesis, the investigation of five PBI derivatives with different frontier energetic levels to produce a reference work of reduced PBIs was tackled.
N2  - Im Rahmen dieser Arbeit wurden die Wechselwirkungen zwischen neuartigen Corannulen-Derivaten sowohl in Lösung als auch im festen Zustand durch Veränderung des Imid-Restes eines literaturbekannten annulierten Corannulen-Dicarboximids untersucht, um ein besseres Verständnis der Packung und des möglichen Ladungstransports in potentiellen Anwendungen zu erhalten. Dementsprechend war es das Ziel der Arbeit, ein elektronenarmes Corannulenbis(dicarboximid) zu synthetisieren und zu untersuchen, das auf bereits veröffentlichten Arbeiten basiert, jedoch eine höhere Löslichkeit und weniger sterischen Anspruch in der Imidposition aufweist, um die Selbstorganisation in Lösung zu ermöglichen.
Um weitere Einblicke in die Konformationsstabilität, Struktur und chiroptischen Eigenschaften von stark verdrillten PBIs zu erhalten, war ein weiteres Ziel dieser Arbeit das Design, die Synthese und die optoelektronische Untersuchung verschiedener vierfach direkt arylierter PBIs durch Substitution in Bucht-Position mit kleineren Kohlenwasserstoffen mit unterschiedlichen sterischen Anforderungen, z.B. Phenyl, Naphthalin und Pyren, die durch chirale Hochleistungsflüssigkeitschromatographie (HPLC) trennbar sein sollten.
Bisher gibt es noch keine übersichtliche Studie über die optischen und elektronischen Eigenschaften von unterschiedlich kernsubstituierten PBIs im neutralen sowie mono- und dianionischen Zustand in Lösung, die auch den Ursprung der unterschiedlichen optischen Übergänge in den Absorptions- und Emissionsspektren aufklärt. In dieser Arbeit wurde daher die Untersuchung von fünf PBI-Derivaten mit unterschiedlichen energetischen Eigenschaften in Angriff genommen, um ein Referenzwerk reduzierter PBIs zu erstellen.
KW  - Corannulene
KW  - Polycyclische Aromaten
KW  - Perylenbisdicarboximide <Perylen-3,4:9,10-bis(dicarboximide)>
KW  - Aggregation
KW  - Chirality
KW  - Reduction
KW  - Perylenbisdicarboximide
KW  - Supramolekulare Chemie
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-247000
ER  - 
TY  - JOUR
A1  - Wu, Zhu
A1  - Dinkelbach, Fabian
A1  - Kerner, Florian
A1  - Friedrich, Alexandra
A1  - Ji, Lei
A1  - Stepanenko, Vladimir
A1  - Würthner, Frank
A1  - Marian, Christel M.
A1  - Marder, Todd B.
T1  - Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature
JF  - Chemistry—A European Journal
N2  - Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T\(^M_1\) state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T\(^A_1\) state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.
KW  - AIE
KW  - luminescence
KW  - phosphorescence
KW  - triarylborane
KW  - triplet
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318297
VL  - 28
IS  - 30
ER  - 
TY  - JOUR
A1  - Wissing, Elmo
A1  - Kaupp, Martin
A1  - Boersma, Jaap
A1  - Spek, Anthony L.
A1  - Koten, Gerard van
T1  - Alkylation Reactions of Dialkylzinc Compounds with 1,4- Diaza- 1,3-butadienes: Cationic and radical Anionic Organozinc Intermediates. Molecular Structure of the Cationic Organozinc Species [MeZn(t-BuN=CHCH=N-t-Bu)]O\(_3\)SCF\(_3\) and Me\(_2\)Zn(bpy)(bpy = 2,2' -Bipyridine)
N2  - No abstract available
KW  - Anorganische Chemie
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60008
ER  - 
TY  - JOUR
A1  - Kim, Jin Hong
A1  - Liess, Andreas
A1  - Stolte, Matthias
A1  - Krause, Ana-Maria
A1  - Stepanenko, Vladimir
A1  - Zhong, Chuwei
A1  - Bialas, David
A1  - Spano, Frank
A1  - Würthner, Frank
T1  - An Efficient Narrowband Near-Infrared at 1040 nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye
JF  - Advanced Materials
N2  - A highly sensitive short-wave infrared (SWIR, λ > 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC\(_{61}\)BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3% and a full-width at half-maximum of only 85 nm (815 cm\(^{-1}\)) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.
KW  - squaraine dyes
KW  - crystal engineering
KW  - J-aggregates
KW  - near-infrared sensitivity
KW  - organic photodiodes
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256374
VL  - 33
IS  - 26
ER  - 
TY  - JOUR
A1  - Seifert, Sabine
A1  - Shoyama, Kazutaka
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - An electron-poor C\(_{64}\) nanographene by palladium-catalyzed cascade C-C bond formation: one-pot synthesis and single-crystal structure analysis
JF  - Angewandte Chemie-International Edition
N2  - Herein, we report the one-pot synthesis of an electron-poor nanographene containing dicarboximide groups at the corners. We efficiently combined palladium-catalyzed Suzuki-Miyaura cross-coupling and dehydrohalogenation to synthesize an extended two-dimensional pi-scaffold of defined size in a single chemical operation starting from N-(2,6-diisopropylphenyl)-4,5-dibromo-1,8-naphthalimide and a tetrasubstituted pyrene boronic acid ester as readily accessible starting materials. The reaction of these precursors under the conditions commonly used for Suzuki-Miyaura cross-coupling afforded a C\(_{64}\) nanographene through the formation of ten C-C bonds in a one-pot process. Single-crystal X-ray analysis unequivocally confirmed the structure of this unique extended aromatic molecule with a planar geometry. The optical and electrochemical properties of this largest ever synthesized planar electron-poor nanographene skeleton were also analyzed.
KW  - Graphene nanoribbons
KW  - Liquid-crystalline
KW  - dyes/pigments
KW  - polycyclic aromatic hydrocarbons
KW  - two-dimensional nanostructures
KW  - Aromatic-hydrocarbon
KW  - Carbon
KW  - Dyes
KW  - Functionalization
KW  - cascade reactions
KW  - nanographene
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188889
VL  - 55
IS  - 22
ER  - 
TY  - JOUR
A1  - Bündgen, P.
A1  - Engels, Bernd
A1  - Peyerimhoff, S.D.
T1  - An MRD-CI study of low-lying electronic states in CaF
N2  - Dipole moments and various spectroscopic constants of some low-lying electronic states of the CaF molecule have been calculated using the multireference single· and double-excitation configuration-interaction (MRD-CI) method. The electronic structure of the highly ionic molecule in various excited states can be explained in tenns of different polarisations of the mainly Cacentered valence electron in the field of the F\(^-\) anion. Plots of natural orbitals occupied by the valence electron in the different states give a qualitative picture of the charge distribution and provide a visualisation of the different polarisations of the valence electron in the various states. Comparisons with the electrostatic polarisation model ofTörring, Ernstand Kändler (TEK model) are made. The unknown A' \(^2 \Delta\) state is predicted to lie about 21200 cm\(^{-1}\) above the ground state.
KW  - Organische Chemie
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58880
ER  - 
TY  - JOUR
A1  - Tshitenge Tshitenge, Dieudonné
A1  - Bruhn, Torsten
A1  - Feineis, Doris
A1  - Mudogo, Virima
A1  - Kaiser, Marcel
A1  - Brun, Reto
A1  - Bringmann, Gerhard
T1  - An unusually broad series of seven cyclombandakamines, bridged dimeric naphthylisoquinoline alkaloids from the Congolese liana Ancistrocladus ealaensis
JF  - Scientific Reports
N2  - A series of seven unusual dimeric naphthylisoquinoline alkaloids was isolated from the leaves of the tropical liana Ancistrocladus ealaensis J. Léonard, 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.
KW  - Screening
KW  - Solution-state NMR
KW  - Stereochemistry
KW  - Structure elucidation
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200759
VL  - 9
ER  - 
TY  - JOUR
A1  - Gittins, C. M.
A1  - Harris, N. A.
A1  - Field, R. W.
A1  - Verges, J.
A1  - Ernst, W. E.
A1  - Bündgen, P.
A1  - Engels, Bernd
T1  - Analysis and Depertubation of the C\(^2\)Π and D\(^2\)Σ\(^+\) states of CaF
N2  - No abstract available
KW  - Organische Chemie
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58980
ER  - 
TY  - JOUR
A1  - Fayez, Shaimaa
A1  - Feineis, Doris
A1  - Aké Assi, Laurent
A1  - Seo, Ean-Jeong
A1  - Efferth, Thomas
A1  - Bringmann, Gerhard
T1  - Ancistrobreveines A–D and related dehydrogenated naphthylisoquinoline alkaloids with antiproliferative activities against leukemia cells, from the West African liana Ancistrocladus abbreviatus
JF  - RSC Advances
N2  - 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.
KW  - chemistry
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201686
VL  - 9
IS  - 28
ER  - 
TY  - JOUR
A1  - Brünnert, Daniela
A1  - Seupel, Raina
A1  - Goyal, Pankaj
A1  - Bach, Matthias
A1  - Schraud, Heike
A1  - Kirner, Stefanie
A1  - Köster, Eva
A1  - Feineis, Doris
A1  - Bargou, Ralf C.
A1  - Schlosser, Andreas
A1  - Bringmann, Gerhard
A1  - Chatterjee, Manik
T1  - Ancistrocladinium A induces apoptosis in proteasome inhibitor-resistant multiple myeloma cells: a promising therapeutic agent candidate
JF  - Pharmaceuticals
N2  - The N,C-coupled naphthylisoquinoline alkaloid ancistrocladinium A belongs to a novel class of natural products with potent antiprotozoal activity. Its effects on tumor cells, however, have not yet been explored. We demonstrate the antitumor activity of ancistrocladinium A in multiple myeloma (MM), a yet incurable blood cancer that represents a model disease for adaptation to proteotoxic stress. Viability assays showed a potent apoptosis-inducing effect of ancistrocladinium A in MM cell lines, including those with proteasome inhibitor (PI) resistance, and in primary MM cells, but not in non-malignant blood cells. Concomitant treatment with the PI carfilzomib or the histone deacetylase inhibitor panobinostat strongly enhanced the ancistrocladinium A-induced apoptosis. Mass spectrometry with biotinylated ancistrocladinium A revealed significant enrichment of RNA-splicing-associated proteins. Affected RNA-splicing-associated pathways included genes involved in proteotoxic stress response, such as PSMB5-associated genes and the heat shock proteins HSP90 and HSP70. Furthermore, we found strong induction of ATF4 and the ATM/H2AX pathway, both of which are critically involved in the integrated cellular response following proteotoxic and oxidative stress. Taken together, our data indicate that ancistrocladinium A targets cellular stress regulation in MM and improves the therapeutic response to PIs or overcomes PI resistance, and thus may represent a promising potential therapeutic agent.
KW  - multiple myeloma
KW  - ancistrocladinium A
KW  - naphthylisoquinoline alkaloids
KW  - proteasome inhibitor resistance
KW  - RNA splicing
KW  - cellular stress response
KW  - proteasome subunit beta type-5 (PSMB5)
KW  - activating transcription factor 4 (ATF4)
KW  - ataxia teleagiectasia mutated (ATM)
KW  - H2A histone family member X (H2AX)
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-362887
SN  - 1424-8247
VL  - 16
IS  - 8
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  - 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  - Becam, Jérôme
A1  - Walter, Tim
A1  - Burgert, Anne
A1  - Schlegel, Jan
A1  - Sauer, Markus
A1  - Seibel, Jürgen
A1  - Schubert-Unkmeir, Alexandra
T1  - Antibacterial activity of ceramide and ceramide analogs against pathogenic Neisseria
JF  - Scientific Reports
N2  - Certain fatty acids and sphingoid bases found at mucosal surfaces are known to have antibacterial activity and are thought to play a more direct role in innate immunity against bacterial infections. Herein, we analysed the antibacterial activity of sphingolipids, including the sphingoid base sphingosine as well as short-chain C\(_{6}\) and long-chain C\(_{16}\)-ceramides and azido-functionalized ceramide analogs against pathogenic Neisseriae. Determination of the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) demonstrated that short-chain ceramides and a ω-azido-functionalized C\(_{6}\)-ceramide were active against Neisseria meningitidis and N. gonorrhoeae, whereas they were inactive against Escherichia coli and Staphylococcus aureus. Kinetic assays showed that killing of N. meningitidis occurred within 2 h with ω–azido-C\(_{6}\)-ceramide at 1 X the MIC. Of note, at a bactericidal concentration, ω–azido-C\(_{6}\)-ceramide had no significant toxic effect on host cells. Moreover, lipid uptake and localization was studied by flow cytometry and confocal laser scanning microscopy (CLSM) and revealed a rapid uptake by bacteria within 5 min. CLSM and super-resolution fluorescence imaging by direct stochastic optical reconstruction microscopy demonstrated homogeneous distribution of ceramide analogs in the bacterial membrane. Taken together, these data demonstrate the potent bactericidal activity of sphingosine and synthetic short-chain ceramide analogs against pathogenic Neisseriae.
KW  - ceramide analogs
KW  - Neisseria
KW  - ceramide
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159367
VL  - 7
ER  - 
TY  - THES
A1  - Abdelmohsen, Usama Ramadan
T1  - Antimicrobial Activities from Plant Cell Cultures and Marine Sponge-Associated Actinomycetes
T1  - Antimikrobielle Aktivitäten aus Pflanzenzellkulturen und marinen Schwamm-assoziierten Actinomyceten
N2  - This thesis is divided into three parts with the main goal allocating novel antimicrobial compounds that could be used as future antibiotics. The first part aimed to evaluate the potential of plant suspension cultures for the production of antimicrobial proteins. The extracellular, intracellular and cell wall bound fractions of seven heterotrophic and photomixotrophic plant cell suspension cultures treated with nine different elicitors were tested for the elicitor dependent production of antimicrobial proteins. Bioactivities were tested against a selected panel of human isolates including Gram-positive and Gram-negative bacteria as well as fungi using the disc diffusion assay. The intracellular fractions of elicited cell cultures were more active than extracellular fractions while the cell wall bound fractions showed lowest activities. Among the 21 fractions tested, the intracellular fraction of Lavendula angustifolia elicited with DC3000 was most active against Candida maltosa. The second most active fraction was the intracellular fraction of Arabidopsis thaliana elicited with salicylic acid which was moreover active against all test strains. The antimicrobial activity of elicited Arabidopsis thaliana cell cultures was tested by bioautography to locate the antimicrobial proteins in the crude extract. The intracellular fraction of photomixotrophic Arabidopsis thaliana cells elicited with salicylic acid was selected for further gel filtration chromatography on S-200 column leading to the purification of one 19 kDa antimicrobially active protein, designated, AtAMP. Our findings suggest that elicited plant cell cultures may present a new promising alternative source of antimicrobial proteins. The second part comprises the isolation of actinomycetes associated with marine sponges and testing the bioactivities of new species for further investigations. Actinobacterial communities of eleven taxonomically different sponges that had been collected from offshore Ras Mohamed (Egypt) and from Rovinj (Croatia) were investigated by a culture-based approach using different standard media for isolation of actinomycetes and media enriched with aqueous sponge extract to target rare and new actinomycete species. Phylogenetic characterization of 52 representative isolates out of 90 based on almost complete sequences of genes encoding 16S rRNA supported their assignment to 18 different actinomycete genera. Altogether 14 putatively new species were identified based on sequence similarity values below 98.2% to other strains in the NCBI database. The use of M1 agar amended with aqueous sponge extract yielded a putative new genus related to Rubrobacter which highlighting the need for innovative cultivation protocols. Biological activity testing showed that five isolates were active against Gram-positives only, one isolate was active against Candida albicans only and one isolate showed activity against both groups of pathogens. Moreover, the antiparasistic activity was documented for four isolates. These results showed a high diversity of actinomycetes associated with marine sponges as well as highlighted their potential to produce anti-infective agents. The third part of the thesis focused on the isolation and structure elucidation of new bioactive compounds. Streptomyces strain RV15 recovered from sponge Dysidea tupha, was selected for further chemical analysis by virtue of the fact that it exhibited the greatest antimicrobial potential against Staphylococcus aureus as well as Candida albicans among the all tested strains. Moreover, members of the genus Streptomyces are well known as prolific producers of interesting pharmacologically active metabolites. Chemical analysis of the methanolic crude extract using different chromatographic tools yielded four new compounds. The structures of the new compounds were spectroscopically elucidated to be four new cyclic peptides, namely, cyclodysidins A-D. Their bioactivity was tested against different proteases, bacteria and Candida as well as tumor cell lines. The compounds did not show any significant activities at this point.
N2  - Die hier vorliegende Dissertation ist in drei Kapitel gegliedert und hatte die Bereitstellung neuer antimikrobieller Substanzen, die zukünftig als Antibiotika genutzt werden könnten, zum Hauptziel. Das erste Kapitel befasst sich mit dem Potenzial von Pflanzen zur Produktion von Proteinen mit antimikrobieller Wirkung. Pflanzenzellkulturen wurden mit neun verschiedenen Induktoren stimuliert und anschließend auf die Produktion von Proteinen mit antimikrobieller Wirkung hin untersucht. Dafür wurden die extra-, intrazellulären sowie die membrangebundenen Proteinfraktionen von sieben heterotrophen und photomixotrophen Pflanzenzellkulturen extrahiert. Mittels Diffusionstests wurden die Wirkung der Proteine gegen eine Sammlung menschlicher Pathogene inklusive Gram-positiver und Gram-negativer Bakterien, sowie Pilze getestet. Die intrazellulären Fraktionen zeigten dabei höhere Aktivitäten als die extrazellulären, wohingegen die membrangebundenen Proteine die geringsten Aktivitäten aufwiesen. Von den insgesamt 21 getesteten Proteinfraktionen wies die mit DC3000 induzierte intrazelluläre Fraktion von Lavendula angustifolia die größte Wirkung gegen Candida maltosa auf. Die mit Salicylsäure induzierte intrazelluläre Proteinfraktion von Arabidopsis thaliana zeigte eine Hemmung aller getesteten pathogenen Stämme. Die antimikrobielle Aktivität der induzierten Arabidopsis thaliana-Zellkultur wurde mittels Bioautography weiter untersucht, um das wirksame Protein im Gesamt-(Roh-) extrakt einzugrenzen. Die intrazelluläre Fraktion der photomixotrophen Arabidopsis thaliana-Zellkultur wurde ausgewählt, um ein 19 kDa Protein mit antimikrobieller Wirkung, genannt AtAMP, mittels Gelfitrationschromatography über eine S-200 Säule aufzureinigen. Unsere Ergebnisse weisen darauf hin, dass induzierte Pflanzenzellkulturen zukünftig als aussichtsreiche alternative Quelle für antimikrobiell wirksame Proteine herangezogen werden können. Der zweite Teil dieser Dissertation beinhaltet die Isolation von mit marinen Schwämmen assoziierten Actinomyceten und deren Testung auf Bioaktivität. Aus 11 taxonomisch verschiedenen, an den Küsten von Ras Mohamed (Ägypten) und Rovinj (Kroatien) gesammelten Schwammspezies, wurden Actinobakterien auf verschiedenen Standardmedien kultiviert. Um seltene, neue Stämme zu isolieren, wurden diese Medien mit wässrigen Schwammextrakten angereichert. Die auf der 16S rRNA-Gensequenz basierenden phylogenetischen Charakterisierung von 52 der insgesamt 90 Isolate, zeigte die Zugehörigkeit zu 18 verschiedenen Actinomyceten-Gattungen. Die 16S rRNA-Gene von 14 Isolaten zeigten Homologien von weniger als 98,2% zu denen anderer in Datenbanken abgelegten Bakterien und stellen somit vermutlich neue Arten dar. Die Verwendung von mit Schwammextrakt angereichertem M1-Agar resultierte in der Kultivierung einer mutmaßlich neuen, mit Rubrobacter verwandten Gattung und bestätigt die Notwendigkeit der Entwicklung neuer innovativer Kultivierungsprotokolle. Aktivitätstests von fünf Isolaten zeigten deren hemmende Wirkung nur gegen Gram-positive Bakterien, ein Isolat zeigte Aktivität nur gegen Candida albicans und ein Isolat war wirksam gegen beide genannten Pathogengruppen. Desweiteren konnten antiparasitäre Wirkungen von vier Isolaten dokumentiert werden. Die hier beschriebenen Ergebnisse zeigen die große Diversität von mit Schwämmen assoziierten Actinomyceten und deren Potential Antiinfektiva zu produzieren. Der dritte Teil dieser Arbeit fokussierte sich auf die Isolation und Strukturaufklärung neuer bioaktiver Substanzen. Streptomyceten sind bekannt für die Produktion von interessanten, pharmakologisch aktiven Metaboliten. Der aus dem Schwamm Dysidea tupha isolierte Stamm Streptomyces RV 15 zeigte eine hohe Aktivität gegen Staphylococcus aureus und C. albicans und wurde deshalb für nähere Untersuchungen ausgewählt. Die chemische Analyse des Methanol-Rohextrakts unter der Verwendung verschiedener Chromatographie-Verfahren resultierte in der Isolation von vier Substanzen. Die spektroskopische Analyse zeigte, dass diese neuen Substanzen zyklische Peptidstrukturen aufweisen und wurden daraufhin als Cyclodysidin A-D benannt. Die Bioaktivitäten dieser Substanzen wurden gegen verschiedene Proteasen, Bakterien und Candida sowie gegen verschiedene Tumorzelllinien getestet. Bis zum jetzigen Zeitpunkt zeigte keine der getesteten Peptide eine aussagekräftige Wirkung.
KW  - Antimikrobieller Wirkstoff
KW  - Pflanzenzelle
KW  - Zellkultur
KW  - Antimikrobielle Aktivitäten
KW  - Pflanzenzellkulturen
KW  - Proteinen mit antimikrobieller Wirkung
KW  - Actinomyceten
KW  - zyklische Peptide
KW  - Antimicrobial activities
KW  - Plant cell cultures
KW  - Antimicrobial proteins
KW  - Actinomycetes
KW  - Cyclic peptides
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-51483
ER  - 
TY  - JOUR
A1  - Tshitenge, Dieudonné Tshitenge
A1  - Feineis, Doris
A1  - Mudogo, Virima
A1  - Kaiser, Marcel
A1  - Brun, Reto
A1  - Bringmann, Gerhard
T1  - Antiplasmodial Ealapasamines A-C,'Mixed' Naphthylisoquinoline Dimers from the Central African Liana Ancistrocladus ealaensis
JF  - Scientific Reports
N2  - Three unusual heterodimeric naphthylisoquinoline alkaloids, named ealapasamines A-C (1–3), were isolated from the leaves of the tropical plant Ancistrocladus ealaensis J. Léonard. 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.
KW  - structure elucidation
KW  - stereochemistry
KW  - Ancistrocladus ealaensis
KW  - dimers
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170645
VL  - 7
IS  - 5767
ER  - 
TY  - JOUR
A1  - Mufusama, Jean-Pierre
A1  - Feineis, Doris
A1  - Mudogo, Virima
A1  - Kaiser, Marcel
A1  - Brun, Reto
A1  - Bringmann, Gerhard
T1  - Antiprotozoal dimeric naphthylisoquinolines, mbandakamines B\(_3\) and B\(_4\), and related 5,8′-coupled monomeric alkaloids, ikelacongolines A–D, from a Congolese Ancistrocladus liana
JF  - RSC Advances
N2  - 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.
KW  - chemistry
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201141
VL  - 9
IS  - 21
ER  - 
TY  - THES
A1  - Kiendl, Benjamin
T1  - Application of diamond nanomaterials in catalysis
T1  - Anwendung von Diamantnanomaterialien in der Katalyse
N2  - 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.
N2  - In dieser Arbeit wurde die katalytische Aktivität von Nanodiamant-Partikeln mit unterschiedlichen Dotierungen und Oberflächenterminierungen, sowie von Diamant-Nanomaterialien, die mit Photokatalysatoren auf Rutheniumbasis funktionalisiert wurden, untersucht. Die Verwendung der Materialien in Photoredox-Experimenten und in der photo(elektro)katalytischen Reduktion von CO2 konnte verdeutlicht werden. Für die Verwendung von Diamant-Nanomaterialien in der Photokatalyse wurden erfolgreich Methoden zur Herstellung und Charakterisierung zahlreicher (un)dotierter Nanopartikeln mit unterschiedlicher Oberflächenterminierung entwickelt. Verschiedenartige Photokatalysatoren, die mit Hilfe von Linker-Systemen an Nanodiamant-Partikel angebunden wurden, wurden in der Photoredox-Katalyse und der photoelektrokatalytischen Reduktion von CO2 untersucht.
KW  - Fotokatalyse
KW  - Synthesediamant
KW  - diamond
KW  - nanomaterials
KW  - photocatalysis
KW  - Diamant
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-179415
ER  -