@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{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{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{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{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{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{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{ChristlLang1982,
author = {Christl, Manfred and Lang, R.},
title = {Tricyclo[5.1.0.0\(^{2,8}\)]octa-3,5-diene (Octavalene)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58124},
year = {1982},
abstract = {No abstract available},
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{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{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{KorthMuellerSustmannetal.1987,
author = {Korth, H.-G. and M{\"u}ller, W. and Sustmann, R. and Christl, Manfred},
title = {Rearrangement of Free Radicals, XII. ESR Spectroscopic Study of the Ring Opening of the Homobenzvalenyl Radical},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58376},
year = {1987},
abstract = {Abstraction of an allylic hydrogen atom in homobenzvalene (4) either in solurion by photolyticaßy generated tert-butoxyl radicals or in an adamantane matrix by X-rays produces the homobcnzvalenyl radical (5). which tbennally rearranps · to tbe tropylium ndical (1). In solution tbe activation cnergy for the rate determined step of the reaction sequence was detennined· to be 13.4 ± O.S kcal/mol.},
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{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{ChristlFreundHennebergeretal.1988,
author = {Christl, Manfred and Freund, S. and Henneberger, H. and Kraft, A. and Hauck, J. and Irngartinger, H.},
title = {Several Polycyclic Valence Isomers of Dimethyl [14]Annulene-1,8-dicarboxylate. Reactivity of a "Nonconjugated" Bis(bicyclo[1.1.0]butane)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58413},
year = {1988},
abstract = {Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (5) with benzvalene (4), norbornene, and norbornadiene afforded the azo compounds 7 and 8. Theseare derivatives of 2,3-diazabicyclo[2.2.2]oct-2-ene as is azo compound 3, which had been obtained previously from 5 and 2 equiv of benzvalene (4). The photochemical extrusion of nitrogen from 3, 7, and 8 has been studied. Whereas 7 and 8 on direct irradiation in benzene gave rise exclusively to the bicyclo[2.2.0]hexane derivatives 9 and 10, respectively, from 3 in addition to the bicyclo[2.2.0]hexane 11, the diolefin 1l was formed. Diolefin 12 has cisdouble bonds in the nine-membered ring and is fixed in a boat conformation in a manner so that the two bicyclobutane systems approach each other very closely. This geometry suggests the unusual ring opening of the intermediate 1,4-cyclohexanediyl diradical from a boat conformation, which arises by inversion of the primarily generated boat conformation. Sensitized photolysis of 3 as weilasthat of ll produced the saturated isomer 13 of 11 and 12. The proximity of the bicyclobutane systems in 1l causes unprecedented reactions leading to cage compounds. When ll was heated at 90 °C, a rearrangement to the pentacyclic product 10 took place. Utilization of tetradeuteriated substrate ll-d4 supported a pathway with two diradical intermediates. Behaving in a convcntional manncr, bicyclobutane 9 and bis(bicyclobutane) 11 took up 1 and 2 equiv of thiophenol most probably in a radical-chain addition to give the thioethers 28 and 19, respectively. In contrast, bis(bicyclobutane) ll was converted by 1 equiv of thiophenol into cagc compound 30 in a process involving both the strained a systems. Heating at 80 °C subjected 30 to a reversible Copc rearrangement, resulting in a 6:1 mixture of 31 and 30. When it was treated with bromine, 11 was transformed to cage compound 38. This addition is believed to proceed via a cationic intermediate. The structure of cage compound 10 was established by a singlc-crystal X-ray analysis of dialcohol 11 prepared from 20 and methyllithium.},
subject = {Organische Chemie},
language = {en}
}
@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{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{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{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{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{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{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}
}
@article{ChristlReuchlein1990,
author = {Christl, Manfred and Reuchlein, H.},
title = {Synthesis and NMR Spectra of 2,3-Dihydro-1,3-methanoindene Derivatives and 1,2,3,5-Tetrahydro-1,3-methanopentalene},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58557},
year = {1990},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{BuendgenEngelsPeyerimhoff1991,
author = {B{\"u}ndgen, P. and Engels, Bernd and Peyerimhoff, S.D.},
title = {An MRD-CI study of low-lying electronic states in CaF},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58880},
year = {1991},
abstract = {Dipole moments and various spectroscopic constants of some low-lying electronic states of the CaF molecule have been calculated using the multireference single· and double-excitation configuration-interaction (MRD-CI) method. The electronic structure of the highly ionic molecule in various excited states can be explained in tenns of different polarisations of the mainly Cacentered valence electron in the field of the F\(^-\) anion. Plots of natural orbitals occupied by the valence electron in the different states give a qualitative picture of the charge distribution and provide a visualisation of the different polarisations of the valence electron in the various states. Comparisons with the electrostatic polarisation model ofT{\"o}rring, Ernstand K{\"a}ndler (TEK model) are made. The unknown A' \(^2 \Delta\) state is predicted to lie about 21200 cm\(^{-1}\) above the ground state.},
subject = {Organische Chemie},
language = {en}
}
@article{Engels1991,
author = {Engels, Bernd},
title = {Estimation of the influence of the configurations neglected within truncated MR-CI wavefunctions on molecular properties},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58890},
year = {1991},
abstract = {Reliable prediction of the isotropic hyperfine coupling constant, a\(_{iso}\), is still a difficult task for ab initio calculations. Strong dependence on the method used for its calculation is found. Within a truncated multi-referencc ansatz a\(_{iso}\) is strongly affected by the size ofthe reference space and the nurober of terms in the truncated Cl expansion. In the present paperdifferent effects of the neglected Cl space are discussed. Modified B\(_K\) and A\(_K\) methods are used to estimate the contributions ofthe neglected configurations. lt can be shown that a combination of both methods is able to recover about 90-9 S\% of the total error in a\(_{iso}\)· Furthermore, it was found that to obtain about 90\% of the B\(_K\) correction only about I 0-20\% ofthe configurations within H0 have to be corrected.},
subject = {Organische Chemie},
language = {en}
}
@article{PericEngelsPeyerimhoff1991,
author = {Peric, M. and Engels, Bernd and Peyerimhoff, S.D.},
title = {Ab initio investigation of the vibronic structure of the C\(_2\)H spectrum Calculation of the hyperfine coupling constants for the three lowest lying electronic states},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58901},
year = {1991},
abstract = {The hyperfine coupling constants (isotropic hfcc and four Cartesian components of the ani~ tropic tensor) are calculated for all three atoms of C\(_2\)H in its three lowest-lying electronic states at various molecu)ar geometries by means of the ab initio configuration interaction ( MRO.CI) method. The off-diagonal electronic matrix elements involving the two species ofthe A' symmetry are also computed. A diabatic transforrnation is perforrned Jeading to simple geometrical depen· dences of the hyperline coupling constants.},
subject = {Organische Chemie},
language = {en}
}
@article{PericEngelsPeyerimhoff1991,
author = {Peric, M. and Engels, Bernd and Peyerimhoff, S.D.},
title = {Ab initio investigation of the vibronic structure of the C\(_2\)H spectrum Computation of the vibronically-averaged values for the Hyperfine Coupling Constants},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58915},
year = {1991},
abstract = {The vibronically averaged values for tbe hyperfine coupling constants in the X\(^2 \sum\)-A\(^2 \Pi\) system of the ethynyl radical are computed by means of tbe ab initio metbod calculations. The results point at tbe importance of taking into account the coupling of a1l tbree electronic states in question ( I\(^2\)A', 2\(^2\)A', and 1\(^2\)A") for a reliable explanation of the available experimental findings. The mean values of the hfcc's for K = 0 and 1 levels in \(^{13}\)C\(_2\)H and \(^{13}\)C\(_2\)D in the energy range up to 6000 cm\(^{-1}\) are predicted.},
subject = {Organische Chemie},
language = {en}
}
@article{MarkgrafCortDavisetal.1991,
author = {Markgraf, J. H. and Cort, J. R. and Davis, H. A. and Lindeman, N. I. and Myers, C. R. and Kraft, A. and Christl, Manfred},
title = {Strained Heterocyclic Systems. 20. Basicities of Bicyclic Quinoxalines},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58584},
year = {1991},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{BentleyChristlNorman1991,
author = {Bentley, T. W. and Christl, Manfred and Norman, S. J.},
title = {Methanesulfonate/p-Nitrobenzoate and p-Toluenesulfonate/p-Nitrobenzoate Rate Ratios. Solvolyses of 1-Adamantyl and Benzhydryl Substrates},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58599},
year = {1991},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@article{ReuterEngelsPeyerimhoff1992,
author = {Reuter, W. and Engels, Bernd and Peyerimhoff, S.D.},
title = {The Reaction of Singlet and Triplet Methylen with Ethene - A Multi-Reference CI Study},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58923},
year = {1992},
abstract = {Large-scale multireference configuration interaction (MRD-CI) calculations in a flexible atomic orbital (AO) basis are employed to study the reaction of C\(_2\)H\(_4\) with CH\(_2\) in its firSt triplet and singlet state. The minimum energy path (MEP) of both reactions is calculated, and different mechanisms are discussed. To examine the possible participation of the singlet state in the overall reaction starting from the triplet channel and terminating in the singlet-state c-C\(_3\)H\(_6\), various cuts through both hypersurfaces are calculated. lt is found that favorable interconversion from the trip1et to the singlet surface can only occur at !arge separations of the two fragments of CH2 and C\(_2\)H\(_4\). Experimental data considering the vibrational motion of CH\(_2\) in connection with the relative position of both surfaces are used to obtain an estimate for the overall barrier of the reaction. The height of the barrier is about 6 kcal/mol, while the barrier of the pure triplet reaction is calculated to be 7-9 kcal/mol.},
subject = {Organische Chemie},
language = {en}
}
@article{EngelsPericReuteretal.1992,
author = {Engels, Bernd and Peric, M. and Reuter, W. and Peyerimhoff, S.D. and Grein, F.},
title = {Study of the hyperfine coupling constants \(^{14}\)N and \(^1\)H) of the NH\(_2\) molecule in the X\(^2\)B\(_1\) ground state and the A\(^2\)A\(_1\) excited state},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58937},
year = {1992},
abstract = {The hyperfine coupling constants (hfcc) A\(_{iso}\) and A\(_{ij}\) are calculated for the atoms of NH\(_2\) in its, two lowest-lying electronk states at various molecular geometries by means of the ab initio multireference configuration interaction .method. The vibronically averaged values of the hfccs for the K = 0 and 1 levels in \(^{14}\)N \(^1\)H\(_2\) in the energy range up to 20 000 cm\(^{-1}\) are computed. Polarization elfects which determine A\(_{iso}\) as well as a simple model to describe the dipolar hfccs are discussed. All resrilts are in excellent agreement with experimental data.},
subject = {Organische Chemie},
language = {en}
}
@article{PericEngels1992,
author = {Peric, M. and Engels, Bernd},
title = {Ab initio calculations of the vibronically averaged values for the hyperfine coupling constants in NH\(_2\), NHD and ND\(_2\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58941},
year = {1992},
abstract = {Vibronically averaged values for K =0 and K = 1 bending levels in the energy range between 0 and 25 000 cm\(^{-1}\) are computed for the \(^{14}\)N, H, and D atoms in NH\(_2\), NHD, and ND\(_2\) The pure ab initio electronic potentials, as well as those derived by fitting of experimentally observed band positions are employed. Effects of vibronic coupling and local perturbations of close-lying levels belanging to different electronic states are discussed.},
subject = {Organische Chemie},
language = {en}
}
@article{PericEngels1992,
author = {Peric, M. and Engels, Bernd},
title = {Ab initio calculation of the vibronically averaged hyperfine coupling constants in the 1\(^2\)Π\(_u\) electronic state of CH\(_2 ^+\)},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58951},
year = {1992},
abstract = {The results of pure ab initio calculations of the hyperfine coupling constants for the 1 \(^2 \pi _u\) electronic state for various isotopomers of CHi in the energy range between 0 and 20 000 cm\(^{-1}\) are presented. Effects of vibronic and spin-orbit coupling are discussed.},
subject = {Organische Chemie},
language = {en}
}
@article{ChristlBraunMueller1992,
author = {Christl, Manfred and Braun, Martin and M{\"u}ller, Germar},
title = {1,2,4-Cyclohexatriene, an Isobenzene, and Bicyclo[4.4.0)deca-1,3,5,7,8-pentaene, an Isonaphthalene: Generation and Trapping Reactions},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58639},
year = {1992},
abstract = {No abstract available},
subject = {Organische 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{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{BentleyNormanGerstneretal.1993,
author = {Bentley, T. W. and Norman, S. J. and Gerstner, E. and Kemmer, R. and Christl, Manfred},
title = {Solvolysis of Tricyclo[3.1.0.0\(^{2,6}\)]hex-3-yl and Bicyclo[2.1.1]hex-2-yl Sulfonates},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58689},
year = {1993},
abstract = {No abstract available},
subject = {Organische Chemie},
language = {en}
}
@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{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{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}
}