@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}
}