@article{FayezFeineisAkeAssietal.2019,
author = {Fayez, Shaimaa and Feineis, Doris and Ak{\´e} Assi, Laurent and Seo, Ean-Jeong and Efferth, Thomas and Bringmann, Gerhard},
title = {Ancistrobreveines A-D and related dehydrogenated naphthylisoquinoline alkaloids with antiproliferative activities against leukemia cells, from the West African liana Ancistrocladus abbreviatus},
series = {RSC Advances},
volume = {9},
journal = {RSC Advances},
number = {28},
doi = {10.1039/C9RA03105G},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201686},
pages = {15738-15748},
year = {2019},
abstract = {A unique series of six biaryl natural products displaying four different coupling types (5,10 , 7,10 , 7,80 , and 5,80) were isolated from the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Although at first sight structurally diverse, these secondary metabolites all have in common that they belong to the rare group of naphthylisoquinoline alkaloids with a fully dehydrogenated isoquinoline portion. Among the African Ancistrocladus species, A. abbreviatus is so far only the second one that was found to produce compounds with such a molecular entity. Here, we report on four new representatives, named ancistrobreveines A-D (12-14, and 6). They were identified along with the two known alkaloids 6-O-methylhamateine (4) and entdioncophylleine A (10). The two latter naphthylisoquinolines had so far only been detected in Ancistrocladus species from Southeast Asia. All of these fully dehydrogenated alkaloids have in common being optically active despite the absence of stereogenic centers, due to the presence of the rotationally hindered biaryl axis as the only element of chirality. Except for ent-dioncophylleine A (10), which lacks an oxygen function at C-6, the ancistrobreveines A-D (12-14, and 6) and 6-O-methylhamateine (4) are 6-oxygenated alkaloids, and are, thus, typical 'Ancistrocladaceae-type' compounds. Ancistrobreveine C (14), is the first - and so far only - example of a 7,80-linked fully dehydrogenated naphthylisoquinoline discovered in nature that is configurationally stable at the biaryl axis. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR) and chiroptical (electronic circular dichroism) methods. Ancistrobreveine C (14) and 6-O-methylhamateine (4) exhibited strong antiproliferative activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrugresistant subline, CEM/ADR5000.},
language = {en}
}
@article{MufusamaFeineisMudogoetal.2019,
author = {Mufusama, Jean-Pierre and Feineis, Doris and Mudogo, Virima and Kaiser, Marcel and Brun, Reto and Bringmann, Gerhard},
title = {Antiprotozoal dimeric naphthylisoquinolines, mbandakamines B\(_3\) and B\(_4\), and related 5,8′-coupled monomeric alkaloids, ikelacongolines A-D, from a Congolese Ancistrocladus liana},
series = {RSC Advances},
volume = {9},
journal = {RSC Advances},
number = {21},
doi = {10.1039/C9RA01784D},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201141},
pages = {12034-12046},
year = {2019},
abstract = {From the leaves of a botanically and phytochemically as yet unexplored Ancistrocladus liana discovered in the rainforests of the Central region of the Democratic Republic of the Congo in the vicinity of the town of Ikela, six new naphthylisoquinoline alkaloids were isolated, viz., two constitutionally unsymmetric dimers, the mbandakamines B\(_3\) (3) and B\(_4\) (4), and four related 5,8′-linked monomeric alkaloids, named ikelacongolines A-D (5a, 5b, 6, and 7). The dimers 3 and 4 are structurally unusual quateraryls comprising two 5,8′-coupled monomers linked via a sterically strongly constrained 6′,1′′-connection between their naphthalene units. These compounds contain seven elements of chirality, four stereogenic centers and three consecutive chiral axes. They were identified along with two known related compounds, the mbandakamines A (1) and B\(_2\) (2), which had so far only been detected in two Ancistrocladus species indigenous to the Northwestern Congo Basin. In addition, five known monomeric alkaloids, previously found in related Central African Ancistrocladus species, were isolated from the here investigated Congolese liana, three of them belonging to the subclass of 5,8′-coupled naphthylisoquinoline alkaloids, whereas two compounds exhibited a less frequently occurring 7,8′-biaryl linkage. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR), chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. The mbandakamines B\(_3\) (3) and B\(_4\) (4) displayed pronounced activities in vitro against the malaria parasite Plasmodium falciparum and the pathogen of African sleeping sickness, Trypanosoma brucei rhodesiense.},
language = {en}
}
@article{WawraFeselWidmeretal.2016,
author = {Wawra, Stephan and Fesel, Philipp and Widmer, Heidi and Timm, Malte and Seibel, J{\"u}rgen and Leson, Lisa and Kesseler, Leona and Nostadt, Robin and Hilbert, Magdalena and Langen, Gregor and Zuccaro, Alga},
title = {The fungal-specific beta-glucan-binding lectin FGB1 alters cell-wall composition and suppresses glucan-triggered immunity in plants},
series = {Nature Communications},
volume = {7},
journal = {Nature Communications},
doi = {10.1038/ncomms13188},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-165945},
pages = {13188},
year = {2016},
abstract = {β-glucans are well-known modulators of the immune system in mammals but little is known about β-glucan triggered immunity in planta. Here we show by isothermal titration calorimetry, circular dichroism spectroscopy and nuclear magnetic resonance spectroscopy that the FGB1 gene from the root endophyte Piriformospora indica encodes for a secreted fungal-specific β-glucan-binding lectin with dual function. This lectin has the potential to both alter fungal cell wall composition and properties, and to efficiently suppress β-glucan-triggered immunity in different plant hosts, such as Arabidopsis, barley and Nicotiana benthamiana. Our results hint at the existence of fungal effectors that deregulate innate sensing of β-glucan in plants.},
language = {en}
}
@article{RonaldHoebartner2020,
author = {Ronald, Micura and H{\"o}bartner, Claudia},
title = {Fundamental studies of functional nucleic acids: aptamers, riboswitches, ribozymes and DNAzymes},
series = {Chemical Society Reviews},
journal = {Chemical Society Reviews},
edition = {Advance Article},
doi = {10.1039/D0CS00617C},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212133},
year = {2020},
abstract = {This review aims at juxtaposing common versus distinct structural and functional strategies that are applied by aptamers, riboswitches, and ribozymes/DNAzymes. Focusing on recently discovered systems, we begin our analysis with small-molecule binding aptamers, with emphasis on in vitro-selected fluorogenic RNA aptamers and their different modes of ligand binding and fluorescence activation. Fundamental insights are much needed to advance RNA imaging probes for detection of exo- and endogenous RNA and for RNA process tracking. Secondly, we discuss the latest gene expression-regulating mRNA riboswitches that respond to the alarmone ppGpp, to PRPP, to NAD+, to adenosine and cytidine diphosphates, and to precursors of thiamine biosynthesis (HMP-PP), and we outline new subclasses of SAM and tetrahydrofolate-binding RNA regulators. Many riboswitches bind protein enzyme cofactors that, in principle, can catalyse a chemical reaction. For RNA, however, only one system (glmS ribozyme) has been identified in Nature thus far that utilizes a small molecule - glucosamine-6-phosphate - to participate directly in reaction catalysis (phosphodiester cleavage). We wonder why that is the case and what is to be done to reveal such likely existing cellular activities that could be more diverse than currently imagined. Thirdly, this brings us to the four latest small nucleolytic ribozymes termed twister, twister-sister, pistol, and hatchet as well as to in vitro selected DNA and RNA enzymes that promote new chemistry, mainly by exploiting their ability for RNA labelling and nucleoside modification recognition. Enormous progress in understanding the strategies of nucleic acids catalysts has been made by providing thorough structural fundaments (e.g. first structure of a DNAzyme, structures of ribozyme transition state mimics) in combination with functional assays and atomic mutagenesis.},
language = {en}
}
@article{PimentelElardoBubackGulderetal.2011,
author = {Pimentel-Elardo, Sheila M. and Buback, Verena and Gulder, Tobias A. M. and Bugni, Tim S. and Reppart, Jason and Bringmann, Gerhard and Ireland, Chris M. and Schirmeister, Tanja and Hentschel, Ute},
title = {New Tetromycin Derivatives with Anti-Trypanosomal and Protease Inhibitory Activities},
series = {Marine drugs},
volume = {9},
journal = {Marine drugs},
number = {10},
doi = {10.3390/md9101682},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-141171},
pages = {1682-1697},
year = {2011},
abstract = {Four new tetromycin derivatives, tetromycins 1-4 and a previously known one, tetromycin B (5) were isolated from Streptomyces axinellae Pol001(T) cultivated from the Mediterranean sponge Axinella polypoides. Structures were assigned using extensive 1D and 2D NMR spectroscopy as well as HRESIMS analysis. The compounds were tested for antiparasitic activities against Leishmania major and Trypanosoma brucei, and for protease inhibition against several cysteine proteases such as falcipain, rhodesain, cathepsin L, cathepsin B, and viral proteases SARS-CoV M(pro), and PL(pro). The compounds showed antiparasitic activities against T. brucei and time-dependent inhibition of cathepsin L-like proteases with K(i) values in the low micromolar range.},
language = {en}
}
@article{WalterCollenburgJaptoketal.2016,
author = {Walter, T. and Collenburg, L. and Japtok, L. and Kleuser, B. and Schneider-Schaulies, S. and M{\"u}ller, N. and Becam, J. and Schubert-Unkmeir, A. and Kong, J. N. and Bieberich, E. and Seibel, J.},
title = {Incorporation and visualization of azido-functionalized N-oleoyl serinol in Jurkat cells, mouse brain astrocytes, 3T3 fibroblasts and human brain microvascular endothelial cells},
series = {Chemical Communications},
volume = {52},
journal = {Chemical Communications},
number = {55},
doi = {10.1039/c6cc02879a},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191263},
pages = {8612-8614},
year = {2016},
abstract = {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.},
language = {en}
}
@article{WaechtlerKuebelBarthelmesetal.2016,
author = {W{\"a}chtler, Maria and K{\"u}bel, Joachim and Barthelmes, Kevin and Winter, Andreas and Schmiedel, Alexander and Pascher, Torbj{\"o}rn and Lambert, Christoph and Schubert, Ulrich S. and Dietzek, Benjamin},
title = {Energy transfer and formation of long-lived \(^3\)MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands},
series = {Physical Chemistry Chemical Physics},
volume = {18},
journal = {Physical Chemistry Chemical Physics},
number = {4},
doi = {10.1039/c5cp04447b},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191041},
pages = {2350-2360},
year = {2016},
abstract = {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.},
language = {en}
}
@article{KarGehrigAllampallyetal.2016,
author = {Kar, Haridas and Gehrig, Dominik W. and Allampally, Naveen Kumar and Fern{\´a}ndez, Gustavo and Laquai, Fr{\´e}d{\´e}ric and Ghosh, Suhrit},
title = {Cooperative supramolecular polymerization of an amine-substituted naphthalene-diimide and its impact on excited state photophysical properties},
series = {Chemical Science},
volume = {7},
journal = {Chemical Science},
number = {2},
doi = {10.1039/c5sc03462k},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191459},
pages = {1115-1120},
year = {2016},
abstract = {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.},
language = {en}
}
@article{SulimanSunPedersenetal.2016,
author = {Suliman, Salwa and Sun, Yang and Pedersen, Torbjorn O. and Xue, Ying and Nickel, Joachim and Waag, Thilo and Finne-Wistrand, Anna and Steinm{\"u}ller-Nethl, Doris and Krueger, Anke and Costea, Daniela E. and Mustafa, Kamal},
title = {In vivo host response and degradation of copolymer scaffolds functionalized with nanodiamonds and bone morphogenetic protein 2},
series = {Advanced Healthcare Materials},
volume = {5},
journal = {Advanced Healthcare Materials},
number = {6},
doi = {10.1002/adhm.201500723},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-189764},
pages = {730-742},
year = {2016},
abstract = {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.},
language = {en}
}
@article{CeymanRosspeintnerSchrecketal.2016,
author = {Ceyman, Harald and Rosspeintner, Arnulf and Schreck, Maximilian H. and M{\"u}tzel, Carina and Stoy, Andreas and Vauthey, Eric and Lambert, Christoph},
title = {Cooperative enhancement versus additivity of two-photon-absorption cross sections in linear and branched squaraine superchromophores},
series = {Physical Chemistry Chemical Physics},
volume = {18},
journal = {Physical Chemistry Chemical Physics},
number = {24},
doi = {10.1039/c6cp02312f},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188299},
pages = {16404-16413},
year = {2016},
abstract = {The linear and nonlinear optical properties of a series of oligomeric squaraine dyes were investigated by one-photon absorption spectroscopy (1PA) and two-photon absorption (2PA) induced fluorescence spectroscopy. The superchromophores are based on two indolenine squaraine dyes with transoid (SQA) and cisoid configuration (SQB). Using these monomers, linear dimers and trimers as well as star-shaped trimers and hexamers with benzene or triphenylamine cores were synthesised and investigated. The red-shifted and intensified 1PA spectra of all superchromophores could well be explained by exciton coupling theory. In the linear chromophore arrangements we also found superradiance of fluorescence but not in the branched systems. Furthermore, the 2PA showed enhanced cross sections for the linear oligomers but only additivity for the branched systems. This emphasizes that the enhancement of the 2PA cross section in the linear arrangements is probably caused by orbital interactions of higher excited configurations.},
language = {en}
}
@article{KraftStanglKrauseetal.2017,
author = {Kraft, Andreas and Stangl, Johannes and Krause, Ana-Maria and M{\"u}ller-Buschbaum, Klaus and Beuerle, Florian},
title = {Supramolecular frameworks based on [60]fullerene hexakisadducts},
series = {Beilstein Journal of Organic Chemistry},
volume = {13},
journal = {Beilstein Journal of Organic Chemistry},
doi = {10.3762/bjoc.13.1},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171996},
pages = {1-9},
year = {2017},
abstract = {[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.},
language = {en}
}
@article{FayezFeineisMudogoetal.2017,
author = {Fayez, Shaimaa and Feineis, Doris and Mudogo, Virima and Awale, Suresh and Bringmann, Gerhard},
title = {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},
series = {RSC Advances},
volume = {7},
journal = {RSC Advances},
number = {85},
doi = {10.1039/c7ra11200a},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172008},
pages = {53740-53751},
year = {2017},
abstract = {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.},
language = {en}
}
@article{SpenstYoungWasielewskietal.2016,
author = {Spenst, Peter and Young, Ryan M. and Wasielewski, Michael R. and W{\"u}rthner, Frank},
title = {Guest and solvent modulated photo-driven charge separation and triplet generation in a perylene bisimide cyclophane},
series = {Chemical Science},
volume = {7},
journal = {Chemical Science},
number = {8},
doi = {10.1039/c6sc01574c},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191252},
pages = {5428-5434},
year = {2016},
abstract = {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.},
language = {en}
}
@article{PloetzPolyutovIvanovetal.2016,
author = {Pl{\"o}tz, P.-A. and Polyutov, S. P. and Ivanov, S. D. and Fennel, F. and Wolter, S. and Niehaus, T. and Xie, Z. and Lochbrunner, S. and W{\"u}rthner, Frank and K{\"u}hn, O.},
title = {Biphasic aggregation of a perylene bisimide dye identified by exciton-vibrational spectra},
series = {Physical Chemistry Chemical Physics},
volume = {18},
journal = {Physical Chemistry Chemical Physics},
number = {36},
doi = {10.1039/c6cp04898f},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-187387},
pages = {25110-25119},
year = {2016},
abstract = {The quantum efficiency of light emission is a crucial parameter of supramolecular aggregates that can be tuned by the molecular design of the monomeric species. Here, we report on a strong variation of the fluorescence quantum yield due to different phases of aggregation for the case of a perylene bisimide dye. In particular, a change of the dominant aggregation character from H- to J-type within the first aggregation steps is found, explaining the observed dramatic change in quantum yield. This behaviour is rationalised by means of a systematic study of the intermolecular potential energy surfaces using the time-dependent density functional based tight-binding (TD-DFTB) method. This provides a correlation between structural changes and a coupling strength and supports the notion of H- type stacked dimers and J-type stack-slipped dimers. The exciton-vibrational level structure is modelled by means of an excitonic dimer model including two effective vibrational modes per monomer. Calculated absorption and fluorescence spectra are found to be in reasonable agreement with experimental ones, thus supporting the conclusion on the aggregation behaviour.},
language = {en}
}
@article{MezaChinchaLindnerSchindleretal.2020,
author = {Meza-Chincha, Ana-Lucia and Lindner, Joachim O. and Schindler, Dorothee and Schmidt, David and Krause, Ana-Maria and R{\"o}hr, Merle I. S. and Mitrić, Roland and W{\"u}rthner, Frank},
title = {Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation},
issn = {2041-6539},
doi = {10.1039/d0sc01097a},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204653},
year = {2020},
abstract = {Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites.},
language = {en}
}
@article{GershbergFennelRehmetal.2016,
author = {Gershberg, Jana and Fennel, Franziska and Rehm, Thomas H. and Lochbrunner, Stefan and W{\"u}rthner, Frank},
title = {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},
series = {Chemical Science},
volume = {7},
journal = {Chemical Science},
number = {3},
doi = {10.1039/c5sc03759j},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191428},
pages = {1729-1737},
year = {2016},
abstract = {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.},
language = {en}
}
@article{GrandeSoberatsHerbstetal.2018,
author = {Grande, Vincenzo and Soberats, Bartolome and Herbst, Stefanie and Stepanenko, Vladimir and W{\"u}rthner, Frank},
title = {Hydrogen-bonded perylene bisimide J-aggregate aqua material},
volume = {9},
issn = {2041-6539},
doi = {10.1039/C8SC02409J},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204715},
pages = {6904-6911},
year = {2018},
abstract = {A new twelvefold methoxy-triethyleneglycol-jacketed tetraphenoxy-perylene bisimide (MEG-PBI) amphiphile was synthesized that self-assembles into two types of supramolecular aggregates in water: red-coloured aggregates of low order and with weak exciton coupling among the PBIs and blue-coloured strongly coupled J-aggregates consisting of a highly ordered hydrogen-bonded triple helix of PBIs. At room temperature this PBI is miscible with water at any proportions which enables the development of robust dye aggregates in solution, in hydrogel states and in lyotropic liquid crystalline states. In the presence of 60-95 wt\% water, self-standing coloured hydrogels exhibit colour changes from red to blue accompanied by a fluorescence light-up in the far-red region upon heating in the range of 30-50 °C. This phenomenon is triggered by an entropically driven temperature-induced hydrogen-bond-directed slipped stacking arrangement of the MEG-PBI chromophores within structurally well-defined J-aggregates. This versatile aqua material is the first example of a stable PBI J-aggregate in water. We anticipate that this study will open a new avenue for the development of biocompatible functional materials based on self-assembled dyes and inspire the construction of other hydrogen-bonded supramolecular materials in the highly competitive solvent water.},
language = {en}
}
@article{FarrellGrandeSchmidtetal.2019,
author = {Farrell, Jeffrey M. and Grande, Vincenzo and Schmidt, David and W{\"u}rthner, Frank},
title = {A Highly Warped Heptagon-Containing sp\(^2\) Carbon Scaffold via Vinylnaphthyl π-Extension},
series = {Angewandte Chemie International Edition},
volume = {58},
journal = {Angewandte Chemie International Edition},
number = {46},
doi = {10.1002/anie.201909975},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206682},
pages = {16504-16507},
year = {2019},
abstract = {A new strategy is demonstrated for the synthesis of warped, negatively curved, all-sp\(^2\)-carbon π-scaffolds. Multifold C-C coupling reactions are used to transform a polyaromatic borinic acid into a saddle-shaped polyaromatic hydrocarbon (2 ) bearing two heptagonal rings. Notably, this Schwarzite substructure is synthesized in only two steps from an unfunctionalized alkene. A highly warped structure of 2 was revealed by X-ray crystallographic studies and pronounced flexibility of this π-scaffold was ascertained by experimental and computational studies. Compound 2 exhibits excellent solubility, visible range absorption and fluorescence, and readily undergoes two reversible one-electron oxidations at mild potentials.},
language = {en}
}
@article{GoerlSoberatsHerbstetal.2016,
author = {G{\"o}rl, Daniel and Soberats, Bartolome and Herbst, Stefanie and Stepanenko, Vladimir and W{\"u}rthner, Frank},
title = {Perylene bisimide hydrogels and lyotropic liquid crystals with temperature-responsive color change},
series = {Chemical Science},
volume = {7},
journal = {Chemical Science},
number = {11},
doi = {10.1039/c6sc02249a},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-162459},
pages = {6786-6790},
year = {2016},
abstract = {The self-assembly of perylene bisimide (PBI) dyes bearing oligo ethylene glycol (OEG) units in water affords responsive functional nanostructures characterized by their lower critical solution temperature (LCST). Tuning of the LCST is realized by a supramolecular approach that relies on two structurally closely related PBI-OEG molecules. The two PBIs socially co-assemble in water and the resulting nanostructures exhibit a single LCST in between the transition temperatures of the aggregates formed by single components. This permits to precisely tune the transition from a hydrogel to a lyotropic liquid crystal state at temperatures between 26 and 51 °C by adjusting the molar fraction of the two PBIs. Owing to concomitant changes in PBI-PBI interactions this phase transition affords a pronounced color change with "fluorescence-on" response that can be utilized as a smart temperature sensory system.},
language = {en}
}
@article{CecilRikanovicOhlsenetal.2011,
author = {Cecil, Alexander and Rikanovic, Carina and Ohlsen, Knut and Liang, Chunguang and Bernhardt, Jorg and Oelschlaeger, Tobias A. and Gulder, Tanja and Bringmann, Gerd and Holzgrabe, Ulrike and Unger, Matthias and Dandekar, Thomas},
title = {Modeling antibiotic and cytotoxic effects of the dimeric isoquinoline IQ-143 on metabolism and its regulation in Staphylococcus aureus, Staphylococcus epidermidis and human cells},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-68802},
year = {2011},
abstract = {Background: Xenobiotics represent an environmental stress and as such are a source for antibiotics, including the isoquinoline (IQ) compound IQ-143. Here, we demonstrate the utility of complementary analysis of both host and pathogen datasets in assessing bacterial adaptation to IQ-143, a synthetic analog of the novel type N,C-coupled naphthyl-isoquinoline alkaloid ancisheynine. Results: Metabolite measurements, gene expression data and functional assays were combined with metabolic modeling to assess the effects of IQ-143 on Staphylococcus aureus, Staphylococcus epidermidis and human cell lines, as a potential paradigm for novel antibiotics. Genome annotation and PCR validation identified novel enzymes in the primary metabolism of staphylococci. Gene expression response analysis and metabolic modeling demonstrated the adaptation of enzymes to IQ-143, including those not affected by significant gene expression changes. At lower concentrations, IQ-143 was bacteriostatic, and at higher concentrations bactericidal, while the analysis suggested that the mode of action was a direct interference in nucleotide and energy metabolism. Experiments in human cell lines supported the conclusions from pathway modeling and found that IQ-143 had low cytotoxicity. Conclusions: The data suggest that IQ-143 is a promising lead compound for antibiotic therapy against staphylococci. The combination of gene expression and metabolite analyses with in silico modeling of metabolite pathways allowed us to study metabolic adaptations in detail and can be used for the evaluation of metabolic effects of other xenobiotics.},
subject = {Staphylococcus aureus},
language = {en}
}
@article{ChristlBruentrup1974,
author = {Christl, Manfred and Br{\"u}ntrup, Gisela},
title = {Diimine Reduction and Ozonolysis of Benzvalene},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57953},
year = {1974},
abstract = {Via reduction of benzvalene (1) with diirnine tricyclo[3.1.0.02•6]hexane is obtained in good yield. The procedure renders 3, which has already been synthesized by Lemal and Shim, accessible much easier and in larger quantities. IH and 13C n.m.r. spectroscopic data are discussed. Both the thermal and the AgBF4-catalyzed rearrangernent of 3 yield 1,3-cyclohexadiene (8). - The ozonolysis of 1 with subsequent LiAIH4-reduction results in cis-I,3- bis(hydroxyrnethyl)cyclobutane (13a).},
subject = {Organische Chemie},
language = {en}
}
@article{HegmannChristlPetersetal.1988,
author = {Hegmann, Joachim and Christl, Manfred and Peters, Karl and Peters, Eva-Maria and Schnering, Hans Georg von},
title = {Die Reaktionskaskade von 6-Oxo-5-phenyl-1,3,4-oxadiazin-2-carbons{\"a}ure-methylester und 1,3-Butadienen zu konjugierten und nichtkonjugierten Cyclopentenonen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58421},
year = {1988},
abstract = {F{\"u}nfgliedrige Carbocyclen sind Bauelemente zahlreicher NaturstofTe und daher attraktive Syntheseziele. Da bisher kein Syntheseverfahren mit großer Anwendungsbreite bekannt ist, sind neue Methoden willkommen. Wir berichten hier {\"u}ber Umsetzungen des Titelheterocyclus 1 mit l,3-Butadienen 1; diese Reaktionen, obwohl vielstufig, liefern im Eintopfverfahren konjugierte und nichtkonjugierte Cyclopentenone und gestatten auch die F{\"u}nfringanellierung.},
subject = {Organische Chemie},
language = {de}
}
@article{EngelsPeyerimhoff1989,
author = {Engels, Bernd and Peyerimhoff, S.D.},
title = {Theoretical study of FC\(_2\)H\(_4\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58824},
year = {1989},
abstract = {Large-scale multireference configuration interaction (MRD-CI) calculations in a quite flexible AO basis are employed to study the energy hypersurface for the reaction intermediate FC\(_2\)H\(_4\) • The reaction F + C\(_2\)H\(_4\) -> FC\(_2\)H\(_4\) as weil as the 1,2 migration of the fluorine atom in FC\(_2\)H\(_4\) is investigated. In addition the rotation around the CC bond in the optimum conformation is studied. The absolute minimum in the potential energy is found for the asymmetric structure but the symmetric structure is also found to be stable with respect to the dissociation, so that a shuttling of the fluorine atom is in principle possible but highly unlikely because ( l) the activation energy is high ( II 5-130 kJ fmol) and the saddle point lies only 4(}-50 kJ jmol below the dissociation Iimit of F + C\(_2\)H\(_4\) and (2) the competitive motion, i.e., rotation around the CC axis, is nearly free (I 1-17 kJ/mol).},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoff1989,
author = {Engels, Bernd and Peyerimhoff, S.D.},
title = {The hyperfine coupling constants of the X\(^3\)Σ\(^-\) state of NH : Influence of polarization functions and configuration space on the description of spin polarization},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58832},
year = {1989},
abstract = {The hyperfine coupling constants for the \(^3\)Σ\(-\) ground state of the NH molecule are determined by configuration interaction calculations whereby the infl.uence of polarization functions as weil as of the configuration space on the spin polarization mechanism is analysed. The dipolar part Au(N) and Au(H) can be obtained very reliably without much computational effort (A .. (N) == -45·3 MHz and A"(H) = -62·3 MHz). The value for the isotropic contribution a1.., in the best AO basis and MRD-CI treatment is - 64·5 MHz for H and 16·6 MHz for nitrogen compared to the corresponding experimental quantities of -66 MHz and 19 MHz respectively. Their determination depends on a subtle balance of the lu, 2u and 3u shell correlation description, whereby the dominant contribution to a1..,(H) results from the 2u shell. It is shown that the often good agreement of a110 values with experiment in a small basis singledouble configuration interaction treatment results from a cancellation of two errors.},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoff1989,
author = {Engels, Bernd and Peyerimhoff, S.D.},
title = {Study of orbital transformations in configurational interaction calculation of hyperfine coupling in nitrogen and CH molecule},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58847},
year = {1989},
abstract = {Multi-reference configuration interaction calculations employing various orbital transformations are undertaken to obtain the isotropic hyperfine coupling constant a\(_{iso\) in nitrogen and a\(_{iso\) (H) in the CH molecule. The natural orbital (NO) basis is found to be more effective than the simple RHF-MO basis; the most obvious is a basis of spin natural orbitals (SNO). It is found that a\(_{iso\) is approached from opposite sides in the NO and 2s shell SNO basis if the CI expansion is increased. Both results are within a few percent of the full CI Iimit for the nitrogen atorn (in the given AO basis) and the experimental value for Hin the CH radical. Various features ofthe SNO are discussed.},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoffSkell1990,
author = {Engels, Bernd and Peyerimhoff, S.D. and Skell, P.S.},
title = {Theoretical study of the potential energy surface governing the stereochemistry in ClC\(_2\)H\(_4\) reactions},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58851},
year = {1990},
abstract = {Large-scale multireference configuration interaction calculations in a double·t·type AO basis including polarization functions are carried out for the potential surface of the ClC\(_2\)H\(_4\9 system. The charge distribution for various extreme points of the surface is discussed. The absolute minimum is found for an asymmetric ClC2H4 structure. The symmetrical bridged nuclear conformation is also found to be stable with respect to dissociation into Cl + C\(_2\)H\(_4\)• The activation energy for rotation about the C-C axis is calculated tobe around 18 kJ/mol, which is comparable tothat for the 1,2 migration {around 26 kJ/mol). The stereochemistry is governed by the fact that addition of CI to C\(_2\)H\(_4\) (or dissociation) is a two-step reaction proceeding through a symmetrica1 intermediate. The direct addition pathway possesses a small barrier of about 8 kJ jmol.},
subject = {Organische Chemie},
language = {en}
}
@article{LeiningerLanzendoerferChristl1983,
author = {Leininger, H. and Lanzend{\"o}rfer, F. and Christl, Manfred},
title = {{\"U}ber die Reduktion des Benzvalenozonids zum cis-1,3-Cyclobutandimethanol mit LiAlH\(_4\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58130},
year = {1983},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{LeiningerChristlWendisch1983,
author = {Leininger, H. and Christl, Manfred and Wendisch, D.},
title = {{\"U}ber die Oxidation von Benzvalen mit Singulett-Sauerstoff zum Bicyclo[1.1.0]butan-endo,endo-2,4-dicarbaldehyd},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58142},
year = {1983},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlLanzendoerferPetersetal.1983,
author = {Christl, Manfred and Lanzend{\"o}rfer, F. and Peters, K. and Peters, E.-M. and Schnering, H. G. von},
title = {Die Reaktionen von 2,5-Diaryl-1,3,4-oxadiazin-6-onen mit trans-Cycloocten, cis,trans-Cyclooctadien und Cyclopropenen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58156},
year = {1983},
abstract = {The transient [4+2]-cycloadducts from the title components eliminate nitrogen to form a 3,4-dihydro-2-pyrone derivative, a tricyclic cyclobutanone derivative and 2,5-dihydrooxepin-2-one derivatives, respectively.},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlLangReimannetal.1984,
author = {Christl, Manfred and Lang, R. and Reimann, W. and Irngartinger, H.},
title = {Darstellung und R{\"o}ntgenstrukturanalyse des Diels-Alder-Addukts von 4-Phenyl-4H-1,2,4-triazol-3,5-dion an Octavalen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58162},
year = {1984},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlLeiningerKemmer1984,
author = {Christl, Manfred and Leininger, H. and Kemmer, P.},
title = {{\"U}ber das cis-Glycol und das Epoxid des Benzvalens},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58174},
year = {1984},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlFreund1985,
author = {Christl, Manfred and Freund, S.},
title = {Substituierte Benzobenzvalene und Diazabenzobenzvalene - Synthesen aus Diels-Alder-Addukten des Benzvalens und NMR-Spektroskopie},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58183},
year = {1985},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlMattauch1985,
author = {Christl, Manfred and Mattauch, B.},
title = {Versuche zur Synthese eines formalen Nitriloxid-Addukts des Benzols. 1,3-Dipolare Cycloadditionen an Bicyclo[2.2.0]hex-5-en-2,3-dicarbons{\"a}ureanhydrid, Dewarbenzol und 1,4-Cyclohexadien},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58216},
year = {1985},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlLanzendoerferGroetschetal.1985,
author = {Christl, Manfred and Lanzend{\"o}rfer, U. and Gr{\"o}tsch, M. M. and Hegmann, J.},
title = {Prim{\"a}raddukt, γ-Ketoketen und einige Folgeprodukte der Reaktion von 6-Oxo-5-phenyl-1,3,4-oxadiazin-2-carbons{\"a}ure-methylester mit Norbornen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58220},
year = {1985},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlHerzogBrueckneretal.1986,
author = {Christl, Manfred and Herzog, C. and Br{\"u}ckner, D. and Lang, R.},
title = {Neue Homobenzvalen-Derivate (Tricylo[4.1.0.0\(^{2,7}\)]hept-3-ene)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58241},
year = {1986},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlLangHerzog1986,
author = {Christl, Manfred and Lang, R. and Herzog, C.},
title = {The Synthesis of Octavalene (Tricyclo[5.1.0.0\(^{2,8}\)]octa-3,5-diene) and Several Substituted Octavalenes},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58254},
year = {1986},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlMattauchIrngartingeretal.1986,
author = {Christl, Manfred and Mattauch, B. and Irngartinger, H. and Goldmann, A.},
title = {Additionen von Benzvalen an Nitriloxide. Eine Synthese f{\"u}r Benzvalen-3-carbonitril},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58269},
year = {1986},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlKemmerMattauch1986,
author = {Christl, Manfred and Kemmer, P. and Mattauch, B.},
title = {1-Methylbenzvalen. Synthese und einige Reaktionen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58270},
year = {1986},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlTuerkPetersetal.1994,
author = {Christl, Manfred and T{\"u}rk, M. and Peters, K. and Peters, E.-M. and Schnering, H. G. von},
title = {Octahydro-1,2,3:4,5,6-dimethenopentalen-2-carbonitril, das erste Derivat eines noch unbekannten (CH)\(_{10}\)-Kohlenwasserstoffs},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58728},
year = {1994},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlTuerkPetersetal.1994,
author = {Christl, Manfred and T{\"u}rk, M. and Peters, K. and Peters, E.-M. and Schnering, H. G. von},
title = {Octahydro-1,2,3:4,5,6-dimethenopentalene-2-carbonitrile, the First Derivative of a Yet-Unknown (CH)\(_{10}\)-Hydrocarbon},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58731},
year = {1994},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{BentleyChristlKemmeretal.1994,
author = {Bentley, T. W. and Christl, Manfred and Kemmer, R. and Llewellyn, G. and Oakley, J. E.},
title = {Kinetic and Spectroscopic Characterisation of Highly Reactive Methanesulfonates. Leaving Group Effects for Solvolyses and Comments on Geminal Electronic Effects Influencing S\(_N\)1 Reactivity},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58748},
year = {1994},
abstract = {Highly reactive methanesulfonates (mesylates, ROMs) have been prepared from 1-phenylethanol. cyclohex-2-en-1-ol, diphenylmethanol and p-methoxybenzyl alcohol by treatment with methanesulfonyl chloride and triethylamine in dichloro- or trichloro-methane at - 20 to 0 °C. The mesylates. characterised in solution by \(^1\)H and \(^{13}\)C NMR at -20 °C, were obtained in satisfactory purity (ca. 95\%) in cold solutions but they decomposed by reaction with chloride, triethylamine or the parent alcohol. Rate constants for solvolyses in aqueous acetone and aqueous ethanol have been determined by a fast response conductimetric method. Product selectivities for solvolyses of pmethoxybenzyl mesylate in aqueous ethanol and methanol at 0 °C have been determined by HPLC. From additional new or Iiterature kinetic data for solvolyses of corresponding bromides. chlorides and p-nitrobenzoates (OPNB). Br/CI. OMs/Br and OMs/OPNB rate ratios were calculated; the results are consistent with electronic effects stabilising the carbocationic transition states and increasing OMs/Br rate ratios for these SN 1 solvolyses; none of the evidence supports a geminal electronic effect on Br/CI rate ratios (e.g. caused by stabilisation of the initial state in pmethoxybenzyl chloride). Steric effects on ester /halide rate ratios for solvolyses of tertiary substrates are confirmed. Relative rates over a 10\(^{16}\) range for ester and halide leaving groups are evaluated for solvolyses of 1-phenylethyl substrates in 80\% ethanol-water. updating previous work by Noyce et al. (1972).},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoff1986,
author = {Engels, Bernd and Peyerimhoff, S. D.},
title = {Theoretical study of the bridging in β-Halo Ethyl},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58779},
year = {1986},
abstract = {Large-acale multi-reference configuration interaction (MRD-CI) calculations in a quite flexible AO basis are employed to study the energy hypersurface for the reaction intermediates XC\(_3\)H\(_4\) with X = Cl, Br and F. Particular emphasis is therby placed on determining the equilibrium conformations, the CH\(_2\) rotation barrier and the energy surface for a possible bridging (shuttling motion (1a] of X between the two carbon centers). The absolute minimum in the potential energy surface is found in all three cases for the asymmetric ß-halo radical in general agreement with ESR data at an XCC angle of ca. 110°, a c-c separation somewhat shorter than a single bond and an approximate sp3 type hybridization (\(\alpha _2 \approx \) 135-140°). In FC\(_2\)H\(_4\) the energy difference between the minimum in the symmetric conformation and the absolute minimum is found to be more than 30 kcal so that shuttling seems impossible in agreement with experimental findings. In BrC\(_2\)H\(_4\) the difference between these two potential minima is only between 1-2 kcal, i.e., smaller than the barrier to CH\(_2\), rotation, so that· shuttling is favored, while ClC\(_2\)H\(_4\) takes an intermediate position between these extremes. The use of correlated wavefunctions is found to be quite important for such a study; the results are related to various kinetic studies of these radicals.},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoffDavidson1987,
author = {Engels, Bernd and Peyerimhoff, S.D. and Davidson, E.R.},
title = {Calculation of hyperfine coupling constants : An ab initio MRD-CI study for nitrogen to analyse the effects of the basis sets and CI parameter},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58784},
year = {1987},
abstract = {The hyperfine coupling constant for the nitrogen atom is evaluated by large-scale MRD-CI calculations. A detailed analysis of the charge density at the nucleus and the spin polarization in the ls and 2s shell as a function of various technical parameters is undertaken. Various (s, p) AO basis sets and the inftuence of correlation orbitals is investigated as weil as selection threshold and other properlies in CI calculations. The best value, obtained for the isotropic hyperfine coupling constant in an s, p, d basis, based on theoretical judgment of' best' quantities, is 9·9 MHz compared to 10·4509 MHz.},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoff1988,
author = {Engels, Bernd and Peyerimhoff, S.D.},
title = {Study of the 1s and 2s shell contributions to the isotropic hyperfine coupling constant in nitrogen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58793},
year = {1988},
abstract = {The istropic part of the hyperfine coupling constant is investigated by means of multireference configuration interaction calculations employing Gaussian basis sets. A detailed study of the 1s and 2s spin polarisation in the nitrogen atom and the NH molecule shows that the structure of the lower-energy space of the unoccupied orbitals is essential for the results. A contraction of the Gaussian basis is possible without loss of accuracy if enough flexibility is retained to describe the main features of the original space of unoccupied functions. Higher than double excitations are found to be non-negligible for the description of α\(_{iso}\).},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPeyerimhoffKarnaetal.1988,
author = {Engels, Bernd and Peyerimhoff, S.D. and Karna, S.P. and Grein, F.},
title = {The hyperfine coupling constants of the five lowest states of CH : An ab initio MRD-CI study},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58807},
year = {1988},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{KarnaGreinEngelsetal.1989,
author = {Karna, S. and Grein, F. and Engels, Bernd and Peyerimhoff, S.D.},
title = {The hyperfine coupling constants of \(^{19}\)F\(_2\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58817},
year = {1989},
abstract = {The isotropic (a\(_{iso}\)) and dipolar (A\(_{dip}\)) hyperfine coupling constants of 19F2 were obtained from MRD-CI wave functions using a variety of basis sets. In series I, increasing numbers of d functions were added to a 5s4p contracted Huzinaga!Dunning basis. In series II, the 5s3p basis set was uncontracted in several steps until 9s5p was reached, to which were added from one to three d-polarization functions. Cl parameters (selectioo threshoids and the number of reference coofiguratioos) were also varied. A study of the R dependence of aiso and Adip was perfonned. The best values obtained at R\(_e\) are 260 G for a\(_{iso}\) and 308 G for A\(_{dip}\)• compared with experimental values of about 280 G for a;10 and 320 G for A\(_{dip}\)·},
subject = {Organische Chemie},
language = {en}
}
@article{VolzShinPrinzbachetal.1978,
author = {Volz, H. and Shin, J.-H. and Prinzbach, H. and Babsch, H. and Christl, Manfred},
title = {Stability of Tricyclo[4.1.0.0\(^{2,7}\)]heptenyl-Cations},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58001},
year = {1978},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlFreitagBruentrup1978,
author = {Christl, Manfred and Freitag, G. and Br{\"u}ntrup, G.},
title = {Der Aufbau des Tetracyclo[4.1.0.0\(^{2,4}\).0\(^{3,5}\)]heptan-Systems durch Addition halogensubstituierter Carbene an Benzvalen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58019},
year = {1978},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{KimChristlKochl1990,
author = {Kim, E. and Christl, Manfred and Kochl, J. K.},
title = {Charge-Transfer Cycloaddition of Homobenzvalene with Tetracyanoethylene},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58537},
year = {1990},
abstract = {The transient yellow color observed in the cycloaddition of homobenzvalene (HB) with tetracyanoethylene (TCNE) is associated with the charge-transfer complex [HB, TCNE). The deliberate photoexcitation of [HB,TCNE) affords a mixture of charge-transfer cycloadducts (1, 2, and 3) that differs from that obtained in thermal cycloaddition. The relationship of {HB t TCNE•) radical-ion pair (as the critical reactive intermediate in charge-transfer cycloaddition) to the activation process for thermal cycloaddition is discussed.},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlFreitagBruentrup1978,
author = {Christl, Manfred and Freitag, G. and Br{\"u}ntrup, G.},
title = {Tricyclo[4.1.0.0\(^{2,7}\)]hept-3-ene durch Umlagerung von 7-endo-Brom- und 7-endo-Chlortetracyclo[4.1.0.0\(^{2,4}\).0\(^{3,5}\)]heptanen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58029},
year = {1978},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlHerbert1979,
author = {Christl, Manfred and Herbert, R.},
title = {Unusual Carbon Shielding Effects of Cyclopropanes and Double Bonds in Strained Bicyclo[3.1.0]hexanes and Cyclopentenes},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58038},
year = {1979},
abstract = {Carbon-13 shieldings and one-bond \(^{13}\)C-H coupling constants of bicydo[2.1.1]hexane, bicydo[2.l.l]hex- 2-ene, tricydo[3.1.1.0\(^{2.4}\)]heptane and benzvalene are presented and compared. to the data of related. compounds. H a bicydo[3.1.0]hexane system is part of a rigid skeleton, the cydopropane ring exerts spedfk: 'Y substituent eflects of two ldnds. In the case of the bicyclobexane boat form an upfield shift of the C-3 signal is observed and in tbe esse of the chair form a downfield shift of 15-20 ppm. Compared to the corresponding cydopentanes the double bond in strained cydopentenes causes downfield shifts of the C-4 absorption. 1bis eftect increases witb increasing strain, reaching 8 45.9 ppm maximum in benzvalene. Hence it is tbe only known bicydo[l.l.O]butane baving 8 reversed order of carbon shieldings. The downfield shifts are e:xplained by means of simple orbital interaction schemes.},
subject = {Organische Chemie},
language = {en}
}
@article{HomannQamarSerimetal.2010,
author = {Homann, Arne and Qamar, Riaz-ul and Serim, Sevnur and Dersch, Petra and Seibel, Juergen},
title = {Bioorthogonal metabolic glycoengineering of human larynx carcinoma (HEp-2) cells targeting sialic acid},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-67806},
year = {2010},
abstract = {Sialic acids are located at the termini of mammalian cell-surface glycostructures, which participate in essential interaction processes including adhesion of pathogens prior to infection and immunogenicity. Here we present the synthesis and bioorthogonal metabolic incorporation of the sialic acid analogue N-(1-oxohex-5-ynyl)neuraminic acid (Neu5Hex) into the cell-surface glycocalyx of a human larynx carcinoma cell line (HEp-2) and its fluorescence labelling by click chemistry.},
subject = {Organische Chemie},
language = {en}
}
@article{PratiharGhoshStepanenkoetal.2010,
author = {Pratihar, Pampa and Ghosh, Suhrit and Stepanenko, Vladimir and Patwardhan, Sameer and Grozema, Ferdinand C. and Siebbeles, Laurens D. A. and W{\"u}rthner, Frank},
title = {Self-assembly and semiconductivity of an oligothiophene supergelator},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-67817},
year = {2010},
abstract = {A bis(trialkoxybenzamide)-functionalized quaterthiophene derivative was synthesized and its self-assembly properties in solution were studied. In non-polar solvents such as cyclohexane, this quaterthiophene π-system formed fibril aggregates with an H-type molecular arrangement due to synergistic effect of hydrogen bonding and π-stacking. The self-assembled fibres were found to gelate numerous organic solvents of diverse polarity. The charge transport ability of such elongated fibres of quaterthiophene π-system was explored by the pulse radiolysis time resolved microwave conductivity (PR-TRMC) technique and moderate mobility values were obtained. Furthermore, initial AFM and UV-vis spectroscopic studies of a mixture of our electron-rich quaterthiophene derivative with the electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) revealed a nanoscale segregated assembly of the individual building blocks in the blend.},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlReichRoberts1971,
author = {Christl, Manfred and Reich, H. J. and Roberts, J. D.},
title = {Nuclear Magnetic Resonance Spectroscopy. Carbon-13 Chemical Shifts of Methylcyclopentanes, Cyclopentanols, and Cyclopentyl Acetates},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57862},
year = {1971},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{BastChristlHuisgenetal.1972,
author = {Bast, K. and Christl, Manfred and Huisgen, R. and Mack, W.},
title = {Additionen der Nitriloxide an CN-Mehrfachbindungen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57879},
year = {1972},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlRoberts1972,
author = {Christl, Manfred and Roberts, J. D.},
title = {Nuclear Magnetic Resonance Spectroscopy : Carbon-13 Chemical Shifts of Small Peptides as a Function of pH},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57885},
year = {1972},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{BastChristlHuisgenetal.1973,
author = {Bast, K. and Christl, Manfred and Huisgen, R. and Mack, W. and Sustmann, R.},
title = {Additionen des Benzonitriloxids an olefinische und acetylenische Dipolarophile},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57905},
year = {1973},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlWarrenHawkinsetal.1973,
author = {Christl, Manfred and Warren, J. D. and Hawkins, B. L. and Roberts, J. D.},
title = {\(^{13}\)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},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57894},
year = {1973},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{BastChristlHuisgenetal.1973,
author = {Bast, K. and Christl, Manfred and Huisgen, R. and Sustmann, R.},
title = {Zur Anlagerung des Benzonitriloxids an α,β-unges{\"a}ttigte Carbons{\"a}ureester},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57912},
year = {1973},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{HuisgenChristl1973,
author = {Huisgen, R. and Christl, Manfred},
title = {Reaktionen der Knalls{\"a}ure mit unges{\"a}ttigten Verbindungen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57927},
year = {1973},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{BastChristlHuisgenetal.1973,
author = {Bast, K. and Christl, Manfred and Huisgen, R. and Mack, W.},
title = {Relative Dipolarophilen-Aktivit{\"a}ten bei Cycloadditionen des Benzonitriloxids},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57935},
year = {1973},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlHuisgen1973,
author = {Christl, Manfred and Huisgen, R.},
title = {Orientierungsph{\"a}nomene bei der Cycloaddition aliphatischer und aromatischer Nitriloxide an α,β-unges{\"a}ttigte Carbonester},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57942},
year = {1973},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlHeinemannKristof1975,
author = {Christl, Manfred and Heinemann, U. and Kristof, W.},
title = {Thermal Rearrangement of Some Endo-Endo'-Bridged Bicyclo[1.1.0]butanes},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57967},
year = {1975},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{Christl1975,
author = {Christl, Manfred},
title = {\(^{13}\)-NMR-Spektren von Bicyclo[n.1.0]kohlenwasserstoffen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57977},
year = {1975},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlFreitag1976,
author = {Christl, Manfred and Freitag, G.},
title = {Das Tricyclo[4.1.0.0\(^{2,7}\)]heptenyl-Kation, ein neues Isomer des Tropylium-Ions},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57985},
year = {1976},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlLueddeckeNagyreviNeppeletal.1977,
author = {Christl, Manfred and L{\"u}ddecke, H.-J. and Nagyrevi-Neppel, A. and Freitag, G.},
title = {Einige Diels-Alder-Additionen des Benzvalens},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57992},
year = {1977},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{SchreckChristl1987,
author = {Schreck, Michael and Christl, Manfred},
title = {Generation and Interception of 1-Oxa-3,4-cyclohexadiene},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31601},
year = {1987},
abstract = {No abstract available},
subject = {Chemie},
language = {en}
}
@article{ChristlBraun1989,
author = {Christl, Manfred and Braun, Martin},
title = {Generation and interception of 1-OXA-2,3-Cyclohexadiene and 1,2,4-Cyclohexatriene},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-56566},
year = {1989},
abstract = {The cycloadducts 6 and 7 of tricyc1o[4.1.0.0 2 ,7)hepta- 3,4-diene (~) with styrene and 1,3-butadiene rearrange to unusual products on thermolysis, namely the cycloheptatriene derivatives ~ and 10. 1-0xa-3,4-cyclohexadiene (20) is generated smoothly from 6,6-dichloro-3-oxabicyclo[3.1.0]hexane (22) and n-butyllithium. 1-0xa-2,3-cyclohexadiene (11) is formed from 6-exo-bromo-6-endo-fluoro-2-oxabicyclo[ 3.1.0]hexane (30) and methyllithium. In the presence of activated olefins, this reaction provides an efficient route to 28 and 33 - 38, the trapping products of 21. Interestingly, [2+2]-cycloadditions do not take place at the same double bond of 21 as [4+2]-cycloadditions. The reactions of 1,3-cyclopentadiene and indene with bromofluorocarbene afford 6-exo-bromo-6-endo-fluorobicyclo[3.1.0]hex-2-ene (50) and its benzo derivative ~, respectively. On treatment of these compounds with methyl lithium in the presence of styrene, the interception products 53 and 47 of 1,2,4-cyc10- hexatriene (44) and its benzo derivative 43, respectively, are formed in good yields.},
subject = {Chemie},
language = {en}
}
@article{GleiterBischofChristl1986,
author = {Gleiter, Rolf and Bischof, Peter and Christl, Manfred},
title = {Electronic Structure of Octavalene : Photoelectron Spectroscopic Investigations},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31588},
year = {1986},
abstract = {The He I photoelectron (PE) spectra of octavalene (5) as weil as its hydrogenated products 6-8 have been investigated. The assignment given is based on an empirical comparison of 5-8 with related compounds, a ZDO model, and semiempirical and ab initio calculations. Within the ZDO model the interaction between the buta.diene moiety and the bicyclobutane fragment of 5 is described by a resonance integral of -2.3 eV. The orbitalsequence of 5 is found tobe 2a\(_2\) (\(\pi\)-\(\sigma\)), 9a\(_1\) (\(\sigma\)), 3b1 (\(\pi\) - \(\sigma\)), 1a\(_2\) (\(\sigma\) + \(\pi\)), 2b\(_1\) (\(\sigma\) + \(\pi\)).},
subject = {Chemie},
language = {en}
}
@article{ChristlSchreck1987,
author = {Christl, Manfred and Schreck, Michael},
title = {1,2,3,5,8,8a-Hexahydronaphthalin aus 1,2-Cyclohexadien},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31656},
year = {1987},
abstract = {Reaktionen von 1,3-Butadien und einigen seiner Methylderivate mit 1a und 1- Methyl-1,2-cyclohexadien 1b sowie den {\"U}bergang der [2 + 2]-Cycloaddukte 2 und 3 in das bisher unbekannte 1,2,3,5,8,8a-HexahydronaphthaJin 4a und einige seiner Methylderivate},
subject = {Chemie},
language = {en}
}
@article{ChristlLangHerzogetal.1985,
author = {Christl, Manfred and Lang, Reinhard and Herzog, Clemens and Stangl, Roland and Peters, Karl and Peters, Eva-Maria and Schnering, Hans Georg von},
title = {Reaktion von Homobenzvalen mit Tetracyanethylen : Bildung eines Tetracyandihydrobarbaralan- und eines Tetracyancyclopropan-Derivats},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31839},
year = {1985},
abstract = {In den Reaktionen von Tetracyanethylen (TCNE) und 5,6-Dichlor-2,3-dicyan-p-benzochinon mit Benzvalen haben wir k{\"u}rzlich die ersten Beispiele f{\"u}r die lange gesuchte einstufige 1,4-Cycloaddition eines Alkens an ein Vinylcyclopropan gcfunden(I~J. Sie ist als [(.,2.+.2s)+ 112J-Prozeß der Dicls-Alder-Addition nahe verwandtllbl. Allerdings entsteht das betreffende TCNE-Addukt, ein Dihydrosemibullvalen-Derivat, nur in einer Ausbeute von wenigen Prozent. Die Hauptprodukte gehen aus einer Zwitterionischen Zwischenstufe hervor, die durch Anlagerung von TCNE an die Benzvalen-n-Bindung resultiert. Professor Rolf Huisgen zum 65. Geburtstag gewidmet},
subject = {Chemie},
language = {de}
}
@article{GleiterBischofGubernatoretal.1985,
author = {Gleiter, Rolf and Bischof, Peter and Gubernator, Klaus and Christl, Manfred and Schwager, Luis and Vogel, Pierre},
title = {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},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31845},
year = {1985},
abstract = {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.},
subject = {Chemie},
language = {en}
}
@article{MetropoulosEngelsPeyerimhoff1993,
author = {Metropoulos, B. and Engels, Bernd and Peyerimhoff, S.D.},
title = {On the chemi-ionization reaction O + CH ----> HCO\(^+\)+ e\(^-\). Coollinear O-CH Approach},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58963},
year = {1993},
abstract = {We have investigated theoretically the importance of the O(\(^3\)P)+CH(a\(^4\sum^-\)) and the O(\(^3\)P)+CH(X\(^2\Pi\)) channels in the collinear chemi-ionization reaction O+CH->HCO\(^+\) +e\(^-\). We have found that both channels may lead to chemi-ionization via favorable Franck-Condon overlaps with the states ofthe ionic species.},
subject = {Organische Chemie},
language = {en}
}
@article{Engels1993,
author = {Engels, Bernd},
title = {Study of influences of various excitation classes on ab initio calculated isotropic hyperfine coupling constants},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58973},
year = {1993},
abstract = {Reliable prediction of the isotropic hyperfine coupling constant A\(_{iso}\) is still a difficult task for ab initio calculations. Strang dependence on the method employed for its ca1culation has been found. Within a CI ansatz A\(_{iso}\) is considerably affected by the excitation classes taken into account within the CI calculation. In the present work the influence of various excitation classes on A\(_{iso}\) is examined. Calculations including all single, double, triple and a large part of the quadruple excitations are performed and the individual effects of the excitation classes are studied. It is found that the surprisingly good agreement found for S-CI treatments is due to large error cancellations. The importance of higher than double excitations arises from their indirect influence on the single excitations.},
subject = {Organische Chemie},
language = {en}
}
@article{WissingKauppBoersmaetal.1994,
author = {Wissing, Elmo and Kaupp, Martin and Boersma, Jaap and Spek, Anthony L. and Koten, Gerard van},
title = {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)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60008},
year = {1994},
abstract = {No abstract available},
subject = {Anorganische Chemie},
language = {en}
}
@article{SchreckChristl1987,
author = {Schreck, Michael and Christl, Manfred},
title = {Freisetzung und Abfangreaktionen von 1-Oxa-3,4-cyclohexadien},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31597},
year = {1987},
abstract = {No abstract available},
subject = {Chemie},
language = {de}
}
@article{SuterPlessErnzerhofetal.1994,
author = {Suter, H. U. and Pleß, V. and Ernzerhof, M. and Engels, Bernd},
title = {Difficulties in the Calculation of Electron Spin Resonance Parameters using Density Functional Methods},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59113},
year = {1994},
abstract = {Density functional theory is applied to the calculation ofthe isotropic byperfine coupJing constants in some small molecules. Various functionals are tested. The agreement of the calculated values to experimental data and values obtained from sophisticated ab initio methods depends on the functionals used and the system under consideration. With respect to spin density calculations the functional of Lee, Yang and Parr with Becke's excbange functional (BLYP) is found to give good results for tbe heavier center of the CH and the NH molecule, while the spin densities of other molecules such as OH, H\(_2\)CN, H\(_2\)CO\(^+\), NO and O\(_2\) deviate considerably from experimental and/or other theoretical results (30\%-60\%). In cases where the singly occupied orbital can contribute to the isotropic hyperfine coupling constants, accurate results are obtained. The reason fortbis is analyzed.},
subject = {Organische Chemie},
language = {en}
}
@article{FreundHennebergerChristl1988,
author = {Freund, S. and Henneberger, H. and Christl, Manfred},
title = {Halbk{\"a}figverbindungen aus Diels-Alder-Addukten des Benzvalens mit Cyclopentadien-Derivaten durch Radikalreaktionen mit Thiophenol und Bromtrichlormethan},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58435},
year = {1988},
abstract = {In Diels-Alder-Reaktionen wurden aus Benzvalen (1) und Tetrachlorcyclopentadienon- dimethylacetal sowie Tetrachlorfuran die Addukte 2 bzw. 8 und 9 erhalten. Behandlung von 2 mit Natrium und tert-Butylalkohol ergab das chlorfreie Acetal 3, dessen Doppelbindung sich mit Diimin unter Bildung von 4 abs{\"a}ttigen ließ. Aus dem bekannten Stammkohlenwasserstoff 5 ging analog 6 hervor, und durch Reaktion seines Anions mit Chlorameisens{\"a}ure- methylester entstand der Ester 7. - Die Verbindungen l, 3, 5, 7-9 und das bekannte U wurden mit Thiophenol so behandelt, daß Radikalkettenreaktionen abliefen. Bei 8 trat Addition an die Zentralbindung des Bicyclobutan-Systems ein. Dagegen unterlag bei 2, 9, U und zum Teil bei 3, deren Doppelbindung jeweils der BicycJobutan-Einheit benachbart ist, das Prim{\"a}rradikal der 5-Hexen-1-yl- Cyclopentylrneth.yl-Umlagerung, aus der letztlich 15, ll, 13 bzw. 16 resultierten. Zum Teil bei 3 und vollst{\"a}ndig bei 5 erfolgte die Addition an die Doppelbindung zu 17 bzw. 18, d.h. ohne Beteiligung der benachbarten Bicyclobutan- Einheit. Durch Aktivierung des Bicyclobutan-Systems mit einer Esterfunktion konnte dessen Passivit{\"a}t aufgehoben werden. So entstanden aus 7 das nichtumgelagerte Produkt 19 und das umgelagerte 20. Ihr Verh{\"a}ltnis hing von der Konzentration an Thiophenol ab. - Analog zur Reaktion 1Z + Thiophenol-13 brachte BromtrichJormethan aus 12 das umlagerte Addukt 21 hervor. - Als Nebenprodukt wurde bei der Umsetzung von 12 mit Thiophenol das Chlorwasserstoff-Addukt 14 des ersteren gefunden. Modellreaktionen f{\"u}r die Bildung von 14 sind die Umsetzungen von 12 mit Essigs{\"a}ure und von 3 sowie 5 mit +Nitrobenzoes{\"a}ure zu den Addukten 22, 23 bzw. 24. Seit},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlHennebergerFreund1988,
author = {Christl, Manfred and Henneberger, H. and Freund, S.},
title = {Halbk{\"a}figverbindungen aus Polycyclen mit einem Bicyclo[1.1.0]butan-System und dazu benachbarter Azobr{\"u}cke durch Radikalreaktionen mit Thiophenol und Bromtrichlormethan},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58440},
year = {1988},
abstract = {Aus Benzvalen (J) und 3,6-Bis(2-pyridyl)-l,2,4,5-tetrazin wurde das Dihydropyridazin 2c erhalten, das ebenso wie die bekannten Dihydropyridazine 2a, b mit Cyclopropen in die entsprechende Azoverbindung 3 {\"u}berging. Addition von Thiophenol an 3a, c und 5 lieferte unter Beteiligung des Bicyclobutan-Systems und der Azofunktion die Halbk{\"a}figverbindungen 4a, c bzw. 6. Aus der Umsetzung von 7, in dem die Azobr{\"u}cke durch zwei BicycJobutan- Systeme flankiert ist, mit Thiophenol sowie Bromtrichlormethan gingen die Halbk{\"a}figverbindungen 8 bzw. 9 hervor. An diesen ~eaktionen wirken beide Bicyclobutan-Systeme und die Azofunktion mit.},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlKraft1988,
author = {Christl, Manfred and Kraft, A.},
title = {Tricyclo[3.1.1.0\(^{2,6}\)]hexandion (das Valen des o-Benzochinons), Bicyclo[2.1.1]hexan-2,3-dion und Valene eines Chinoxalins, des Phenazins sowie eines Benzophenazins},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58459},
year = {1988},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlKraft1988,
author = {Christl, Manfred and Kraft, A.},
title = {Tricyclo[3.1.1.0\(^{2,6}\)]hexandion (the Valen of o-Benzochinons), Bicyclo[2.1.1]hexan-2,3-dion and Valene of a Chinoxalins, of Phenazins and of a Benzophenazine},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58462},
year = {1988},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlBrunnRothetal.1989,
author = {Christl, Manfred and Brunn, E. and Roth, W. R. and Lennartz, H.-W.},
title = {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},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58471},
year = {1989},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlBrunnKraftetal.1989,
author = {Christl, Manfred and Brunn, E. and Kraft, A. and Irngartinger, H. and Huber-Patz, U.},
title = {Nichtbindende Wechselwirkungen in zwei 7-Spirotetracyclo[4.1.0.0\(^{2,4}\).0\(^{3,5}\)]heptanen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58489},
year = {1989},
abstract = {Die Reaktion von Tetrachlordiazocyclopentadien mit Be.nzvalen (2) ergab das Fulven-Derivat 3. Dagegen f{\"u}hrten die Umsetzungen von Diazoßuoren und 5-Diazo-10,1 1-dihydro-SH-dibenzo[ a.d]cyclohepten mit 2 zu den erwarteten Spiro-1-pyrazolinen 4 bzw. 5. Die photolytische Abspaltung von Stickstoff aus 4 und 5 lieferte die Spirotetracycloheptane 6 bzw. 7. Die R{\"o}ntgenstrukturanalyse von 6 beweist einen engen Kontakt zwischen je eineßl Wasserstoffatom der Tetracycloheptan- und der Fluoren-Einheit. Dieser kurze Abstand (2.15 A) ruft Winkelaufweitungen hervor und wird auch als Grund f{\"u}r starke Entschirmungen der betreffenden Protonen und eine formal {\"u}ber sieben Bindungen reichende 0.6-Hz-Kopplung zwischen ihnen angesehen. 7 ist das erste chiralc Tetracyclohcptan. Ursache daf{\"u}r ist eine nichtebene Konformation des Siebenrings, der bei Raumtemperatur nicht invertiert. Auf der Basis von NOE-Messungen gelang die Zuordnung der tH-NMR-Signale von 6 und 7.},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlBraun1989,
author = {Christl, Manfred and Braun, Max},
title = {Photocycloadditionen des Benzvalens},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58492},
year = {1989},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{ChristlBraun1989,
author = {Christl, Manfred and Braun, Max},
title = {Photocycloadditions of Benzvalene},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58506},
year = {1989},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{MuehlhaeuserFroudakisZdetsisetal.1994,
author = {M{\"u}hlh{\"a}user, M. and Froudakis, G. and Zdetsis, A. and Engels, Bernd and Flytzanis, N. and Peyerimhoff, S. D.},
title = {Ab initio investigation of the stability of Si\(_3\)C<\(_3\) clusters and their structural and bonding features},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59060},
year = {1994},
abstract = {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.},
subject = {Organische Chemie},
language = {en}
}
@article{WortmannSalehEngelsPeyerimhoff1994,
author = {Wortmann-Saleh, D. and Engels, Bernd and Peyerimhoff, S. D.},
title = {Theoretical Study of the Reaction O(\(^3\)P) + C\(_2\)H\(_4\) and comparison with the \(^3\)CH\(_3\) + C\(_2\)H\(_4\) Reaction},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59076},
year = {1994},
abstract = {The minimum energy path for the reaction O(\(^3\)P\(_g\)) + C\(_2\)H\(_4\)(\(^1\)A\(_g\)) has been calculated by optimizing all relevant geometrical parameters along the approach of oxygen to ethene. A barrier of 4.7 kcal/mol in the \(^3\)A"( ... 9a'\(^2\)- 10a'3a") potential energy surface and an energy difference of 14.4 kcal/mol between the product and the fragments is found at the multireference-configuration interaction level. The corresponding values at the lower-level treatment CASSCF are 9 kcal/mol for the barrier and 9 kcal/mol for the depth of the potential; this shows the importance of inclusion of electron correlation. The barrier for CH\(_2\) rotation for the lowestenergy structure (asymmetric OC\(_2\)H\(_4\)) is around 5 kcal/mol. The energy gap to the first excited state \(^3\)A'( ... 9a'l0a'3a'12) is found tobe 3.6 kcal/mol in MRD-CI calculations at the ground-state minimum. Comparison with \(^3\)CH\(_2\) + C\(_2\)H\(_4\) shows that in this system the lowest-energy surface is \(^3\)A', i.e., the state which is the excited state in 0 + C\(_2\)H\(_4\). This difference in energy ordering of \(^3\)A' and \(^3\)A" states results from the fact that the p\(_x\), p\(_y\), p\(_z\) degeneracy of oxygen orbitals is lifted in \(^3\)CH\(_2\)leading to b\(_1\), b\(_2\). and a\(_1\) MOs whereby the lowest b\(_2\) (a") remains doubly occupied; as a consequence, the reaction pattem between the oxygen and \(^3\)CH\(_2\) approach is different, which is also quite apparent in the calculated charge transfer.},
subject = {Organische Chemie},
language = {en}
}
@article{StaikovaPericEngelsetal.1994,
author = {Staikova, M. and Peric, M. and Engels, Bernd and Peyerimhoff, S. D.},
title = {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},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59089},
year = {1994},
abstract = {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.},
subject = {Organische Chemie},
language = {en}
}
@article{FroudakisZdetsisMuehlhaeuseretal.1994,
author = {Froudakis, G. and Zdetsis, A. and M{\"u}hlh{\"a}user, M. and Engels, Bernd and Peyerimhoff, S. D.},
title = {A comparative ab initio study of the Si\(_2\)C\(_4\), Si\(_3\)C\(_3\), Si\(_4\)C\(_2\) clusters},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59097},
year = {1994},
abstract = {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.},
subject = {Organische Chemie},
language = {en}
}
@article{SuterHuangEngels1994,
author = {Suter, H. U. and Huang, M.-B. and Engels, Bernd},
title = {A Multireference Configuration Interaction Study of the Hyperfine Structure of the Molecules CCO, CNN and NCN in their triplet ground states},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59108},
year = {1994},
abstract = {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.},
subject = {Organische Chemie},
language = {en}
}
@article{GittinsHarrisFieldetal.1993,
author = {Gittins, C. M. and Harris, N. A. and Field, R. W. and Verges, J. and Ernst, W. E. and B{\"u}ndgen, P. and Engels, Bernd},
title = {Analysis and Depertubation of the C\(^2\)Π and D\(^2\)Σ\(^+\) states of CaF},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58980},
year = {1993},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{StaikovaEngelsPericetal.1993,
author = {Staikova, M. and Engels, Bernd and Peric, M. and Peyerimhoff, S. D.},
title = {Ab initio calculation of the vibronically averaged hyperfine coupling constants in the two lowest electronic states of H\(_2\)O\(^+\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58998},
year = {1993},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{StaikovaEngelsPeric1994,
author = {Staikova, M. and Engels, Bernd and Peric, M.},
title = {Ab initio investigation of the hyperfine structure in the 1\(^2\)Π\(_u\)(X\(^2\)A\(_1\), A\(^2\)B\(_1\) system of BH\(_2\))},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59000},
year = {1994},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{Engels1994,
author = {Engels, Bernd},
title = {Detailed study of the configuration selected multi-reference configuration interaction method combined with perturbation theory to correct the wave function},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59019},
year = {1994},
abstract = {A reliable prediction of the isotropic hyperfine coupling constant A\(_{iso}\) is still a difficult task for ab initio calculations. In previous studies, the configuration selected multireference configuration interaction method in combination with perturbation theory to correct the wave function (MRCI/ B\(_K\)) yielded accurate isotropic hyperfine coupling constants very economically. The present study gives a detailed analysis of the MRCI/ B\(_K\) method based on the X\(^2 \pi\) state of CH as a test case. Furthermore, a comparison to various other methods such as Maller-Ptesset perturbation theory and the coupled cluster approach is made. The success of the MRCI/ B\(_K\) method in predicting isotropic hyperfine coupling constants is explained in terms of the inßuence of higher than double excitations.},
subject = {Organische Chemie},
language = {en}
}
@article{SuterEngels1994,
author = {Suter, H. U. and Engels, Bernd},
title = {Theoretical investigation of ESR parameters: H\(_2\)CN and H\(_2\)CO\(^+\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59029},
year = {1994},
abstract = {The hyperfine structure of the two isoelectronic molecules H\(_2\)CN and H\(_2\)CO\(^+\) in their electronic ground state (X\(^2\)B\(_2\)) is studied. The influence of the atomic orbital (AO), basis sets, of the correlation treatment, and of the. equilibrium geometry on the obtained hyperfine propertles 1s - investigated. It is found that the multireference double excitation-configuration interaction (MRD-CI)/ BK treatment in which an MRD-CI wave function is corrected by a modified B\(_K\) method yields equivalent results to quadratic CI [QCISD(T)], coupled cluster single doubles [CCSD(T)), or Brueckner doubled [BD(T)]. Uncertainties in the equilibrium geometries are found to be the major source for discrepancies between theoretically and experimentally determined isotropic hyperfine coupling constants (hfccs). For the heavier centers, the calculated values of the isotropic hfccs agrees nearly perfectly with experimental values (\(\approx\) 1\%-2\%). The calculated values for the hydrogens are too low, but using the equilibrium structure suggested by Yamamoto and Sato [J. Chem. Phys. 96, 4157 ( 1992)], the best estimate deviates by less than 3\%.},
subject = {Organische Chemie},
language = {en}
}
@article{MuehlhaeuserEngelsMarianetal.1994,
author = {M{\"u}hlh{\"a}user, M. and Engels, Bernd and Marian, C. M. and Peyerimhoff, S. D. and Bruna, P. J. and Jansen, M.},
title = {Einfluß der Ladungsverteilung auf die Bindungsl{\"a}ngen im P\(_4\)O\(_6\) Ger{\"u}st bei Verbindungen des Typs P\(_4\)O\(_6\)X},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59034},
year = {1994},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {de}
}
@article{HuangSuterEngels1994,
author = {Huang, M.-B. and Suter, H. U. and Engels, Bernd},
title = {Theoretical Study of the Dimethylamino Radical (CH\(_3\))\(_2\)N and its protonated cation (CH\(_3\))\(_2\)NH\(^+\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59047},
year = {1994},
abstract = {In the present work the dimethylamino radical ( ( CH\(_3\)) \(_2\)N) and its protonated cation ( ( CH\(_3\))\(_2\)NH\(^+\)) are investigated by means of ab initio methods. The geometries of various conformations of both compounds are obtained with UMP2/6·31 G** calculations, while the hyperfine structure and its dependence on the geometry is studied using the MRD-Cl/B\(_K\) method. The two molecules are compared to study the inftuence of the protonation on geometry and hyperfine structure. The effects of the rotational barriers on the hyperfine structures of (CH\(_3\))\(_2\)N, (CH\(_3\)CH\(_2\))\(_2\)N and ( (CH\(_3\))\(_2\)CH)\(_2\)N will be discussed.},
subject = {Organische Chemie},
language = {en}
}
@article{PlessSuterEngels1994,
author = {Pleß, V. and Suter, H. U. and Engels, Bernd},
title = {Ab initio study of the energy difference between the benzene and the cumulene form of the C\(_6\) molecule},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59059},
year = {1994},
abstract = {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.},
subject = {Organische Chemie},
language = {en}
}
@article{KarnaGreinEngelsetal.1990,
author = {Karna, S.P. and Grein, F. and Engels, Bernd and Peyerimhoff, S.D.},
title = {Ab initio configuration-interaction studies of the ground state potential energy and hyperfine coupling constants of \(^{35}\)Cl\(_2^-\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58869},
year = {1990},
abstract = {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;.},
subject = {Organische Chemie},
language = {en}
}
@article{FunkenEngelsPeyerimhoffetal.1990,
author = {Funken, K. and Engels, Bernd and Peyerimhoff, S.D. and Grein, F.},
title = {Study of the hyperfine coupling constants of the moleculs NH2, NHD and ND2},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58875},
year = {1990},
abstract = {In the present paper we c:alculate tbe magnetic hyperfine couplina constants (hfcc) ai.ID and A11 of the ground states of the isotopes NH2, NHD and ND2 using truncated MR..CI methods. Differences from other theoretical methocls and shortoominp of the truncated Cl approach in calculating tlj10 are studied. Polarization effects wbich detennirae ailo. as weU as a simple model to describe the dipolar hfcc's, are discussed. All results are in. excellent aareement with experimental data. lt is shown that ab initio methods are able to obtain reliable values for otf-diaaonal values of A41 which are difficult to measure experimentaDy.},
subject = {Organische Chemie},
language = {en}
}