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  • 1
    Electronic Resource
    Electronic Resource
    On the aromatic character of some ten π-electron systems (1963)
    Springer
    Theoretical chemistry accounts 1 (1963), S. 206-208 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Elektronenstruktur des 1,4,5-triaza-cycloheptadien-2,6 wurde theoretisch untersucht. Das Ergebnis erklärt das Mißlingen von Versuchen, in diesem und verwandten Siebenringsystemen zyklische Konjugation aufzufinden.
    Abstract: Résumé La structure électronique du 1,4,5-triaza-cycloheptadiène-2,6 a été étudiée. Le résultat explique pourquoi une conjugaison cyclique n'a pas été trouvée expérimentalement ni dans ce composé ni dans d'autres systèmes cycliques semblables à sept membres.
    Notes: Abstract The electronic structure of 1,4,5-triaza-cyclohepta-2,6-diene has been studied. The treatment accounts for the failure of detecting, by experiment, a cyclic conjugation in this and related seven membered ring systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526872
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  • 2
    Electronic Resource
    Electronic Resource
    Self consistent field molecular orbital calculation for pyrrole (1963)
    Springer
    Theoretical chemistry accounts 1 (1963), S. 199-205 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Elektronenstruktur und -spektrum des Pyrrols wurden nach, der halbempirischen LCAO SCF MO-Methode untersucht. Unter Einschluß der Konfigurationenwechselwirkung wurden niedrigliegende angeregte Singulettniveaus bei 5,98, 6,74, 7,33 und 8,20 eV (über dem Grundzustand) errechnet, in guter Übereinstimmung mit den experimentellen Werten von etwa 5,88, 6,77 und 7,21 eV. Das Dipolmoment des Moleküls ergibt sich zu 1,84 D, bei einem experimentellen Wert von 1,80 D.Tabellen von (sphärischen) Rumpf-Elektron-Integralen für alle vier Kombinationen von C und N werden angegeben.
    Abstract: Résumé La structure et le spectre électroniques du pyrrole ont été étudiés à l'aide de la méthode sémiempirique LCAO SCF MO. L'interaction de configurations inclue, le calcul donne des états excités à 5,98, 6,74, 7,33 et 8,20 eV (au-dessus de l'état fondamental), en bon accord avec les valeurs expérimentales de 5,88, 6,77 et 7,21 eV. Le moment dipolaire calculé de la molécule est 1,84 D, l'expérience donnant 1,80 D. Des tables d'intégrales d'attraction entre un coeur sphérique et un électron d'un autre atome sont données pour les quatre combinaisons d'atomes C et N.
    Notes: Abstract The electronic structure and spectrum of pyrrole have been studied using the semiempirical LCAO SCF MO method. With configuration interaction included, low excited singlet states are calculated to occur at 5.98 ev, 6,74 ev, 7,33 ev, and 8,20 ev, in good agreement with the experimental values of about 5.88 ev, 6.77 ev, and 7,21 ev. The dipole moment of the molecule is calculated to 1.84 D, to be compared with the experimental value 1.80 D. Tables of coreattraction integrals for combinations of carbon and nitrogen atoms are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526871
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  • 3
    Electronic Resource
    Electronic Resource
    Recensiones (1967)
    Springer
    Theoretical chemistry accounts 7 (1967), S. 256-258 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01045585
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  • 4
    Electronic Resource
    Electronic Resource
    A CNDO-MO calculation of TiCl4 (1969)
    Springer
    Theoretical chemistry accounts 14 (1969), S. 26-38 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Elektronenstruktur des tetraedrischen TiCl4-Moleküls wird im Rahmen des CNDO-MO-Verfahrens untersucht. Dabei werden Metall- und Ligandenorbitale stark variiert und die AbhÄngigkeit der Reihenfolge des MOs sowie die der Energie der Dipol-erlaubten EinelektronenübergÄnge davon verfolgt.
    Abstract: Résumé La structure électronique de la molécule tétraédrique TiCl4 est étudiée dans le cadre des approximations CNDO MO. Les orbitales de valence du métal et du ligand ont été largement variées et l'on a étudiée l'effet de ces variations sur l'ordre des niveaux des orbitales moléculaires et sur les énergies calculées des transitions monoélectroniques permises.
    Notes: Abstract The electronic structure of the tetrahedral molecule TiCl4 is investigated within the CNDO-MO approximations. The metal and ligand valence orbitals have been extensively varied, and the dependency of the ordering of molecular orbital levels and of the calculated energies for the expected electric dipole allowed one-electron transitions with respect to these component atomic orbitals has been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527325
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  • 5
    Electronic Resource
    Electronic Resource
    A CNDO-MO calculation of VCl4 (1970)
    Springer
    Theoretical chemistry accounts 19 (1970), S. 135-154 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Elektronenstruktur von VCl4 wird mittels des CNDO-Verfahrens untersucht, wobei die Metallorbitale mitn = 3 und 4 systematisch variiert wurden. Optimale Werte für V-4s und V-4p werden angegeben, jedoch V-3d und Cl(-δ) ergeben tiefere Energien nur für räumlich ausgedehnte Orbitale. Da die Zustandsfunktion des ungepaarten Elektrons besonders interessierte, wurde für drei verschiedene Fälle gerechnet: 3a 1, 2e und 4t 2-Symmetrie. Im Rahmen des Roothaan'schen Verfahrens für offene Schalen wurden nicht-Diagonal-Faktoren zwischen ganz und teilweise besetzten MO's gleicher Symmetrie vernachlässigt und der dadurch verursachte Fehler an Hand der Überlappungsintegrale abgeschätzt, wobei lediglich der2 E-Zustand schlecht abschneidet. Als Reihenfolge für die nicht doppelt besetzten Orbitale scheint sich 4t 2, 3a 1, 2e, 5t 2 zu ergeben, was interessante Fragen bezüglich des Jahn-Teller-Effektes (Symmetrie2 T 2) aufwirft. Die experimentellen Daten gestatten leider keine eindeutige Bestätigung der Ergebnisse.
    Abstract: Resume Etude de la structure électronique de la molécule tétraédrique VCl4 dans le cadre d'approximations CNDO-MO. Les orbitales 3d, 4s et 4p du metal et les orbitales 3s et 3p du ligand out été systématiquement variées afin d'essayer de minimiser l'energie totale; on a trouve des orbitales ≪optimales≫ V 4s (χ4 = 1,10) et V 4p (d 3 p 2) mais les orbitales de valence V 3d (d n ) et Cl (-δ) ne font que favoriser une plus basse énergie orbitale. Comme la détermination de l'orbitale moléculaire occupeé par l'électron célibataire du vanadium est un des aspects principaux de cette étude, tous les calculs out été effectués en trois versions, en supposant successivement que l'électron célibataire occupe les orbitales moleculaires 3a 1, 2e et 4t 2 (configurations electroniques2 A 1,2 E et2 T 2 respectivement). Les équations de Hartree-Fock ont été résolues par la méthode SCF de Roothan pour couches ouvertes, mais les multiplicateurs non diagonaux entre orbitales moleculaires occupées et paftiellement occupées de même symétrie ont été negliges. Arm d'estimer qualitativement l'erreur ainsi introduite, on a étudié en fonction de la composition en orbitales 3d (d n ) et Cl (-δ) le recouvrement entre les fonctions propres calculées pour les trois configurations2 A 1, 2E et2 T 2. Les intégrales de recouvrement pour les calculs relatifs à2 A 1 et2 T 2 sont raisonnablement faibles, mais l'erreur introduite est importante pour les calculs sur2 E. L'ordre le plus coherent des orbitales moléculaires incomplètes de V Cl4 est: 42 2 〈 3a 1 〈 2e 〈 5t 2. Cette configuration suggérée pour l'ètat2 T 2 introduit de nouveaux aspects dans l'effet dynamique Jahn-Teller de VCl4. Les expérimentales relatives à la structure électronique de VCl4 ont été brièvement résumees, mais elles ne sont pas en measure de confirmer ou d'infirmer nos calculs.
    Notes: Abstract The electronic structure of the tetrahedral molecule VCL4 is investigated within the CNDO-MO approximations. The metal and ligand valence orbitals, 3d, 4s, 4p; and 3s, 3p; respectively, have been systematically varied in an attempt to minimize the total energy; “optimum” V 4s(χ4 = 1.10) and 4p(d 3 p 2) orbitals have been established, but V 3d(d n ) and Cl(-δ) valence orbitals are only seen to favor lower energy for expanded orbitals. Since determining the one-electron molecular orbital level which is occupied by the vanadium lone electron is a major aspect of this investigation, all calculations have been performed in triplicate: calculations assuming the unpaired electron occupies the 3a 1, 2 e and 4t 2 molecular orbital (ground state electronic configurations2 A 1,2 E, and2 T 2, respectively). The Hartree-Fock equations have been solved by Roothaan's SCF method for open shells, but off-diagonal multipliers between filled and partly filled molecular orbitals of the same symmetry have been neglected. As a qualitative estimate of the error introduced by this simplification, the pertinent overlap integrals between the eigenfunctions from calculations for the three possible configurations,2 A 1,2 E, and2 T 2, are investigated as functions of the component 3d(d n ) and Cl(-δ) valence orbitals. The overlap integrals from the relevant2 A 1 and2 T 2 calculations are reasonably small, but the neglect of off-diagonal multipliers in calculations on the2 E state is found to be a poor approximation. An ordering of the non-filled molecular orbitals in VCl4 of 4t 2 〈 3a 1 〈 2e 〈 5t 2 seems most consistent with the numerous calculations. This suggested ground state electronic configuration of2 T 2 introduces new aspects to the consideration of a (dynamic) Jahn-Teller effect in VCl4. Experimental data pertinent to the electronic structure of VCl4 has been briefly summarized, but unfortunately it is inadequate to confirm or deny the present calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185858
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic structure of the permanganate ion (1968)
    Springer
    Theoretical chemistry accounts 11 (1968), S. 8-25 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Elektronenstruktur des Permanganations wurde mit einer halbquantitativen LCAO-MO Methode ohne empirische Parameter behandelt. Die Zustandsfunktionen des Zentralatoms wurden variiert und der Einflu\ symmetrische Änderungen der BindungsabstÄnde untersucht. Um die Gegenwart von Kationen in Lösung und im Kristall zu simulieren, wurden daneben auch Rechnungen durchgeführt, bei denen einer stÄrkeren Elektronenanziehung durch die Liganden Rechnung getragen wird. Ferner wurde versucht, das Absorptionsspektrum von MnO 4 − auf Grund der vorausgesagten Bandenform und übergangsenergien zu deuten.
    Abstract: Résumé La structure électronique de l'ion permanganate est étudiée à l'aide d'une méthode LCAO MO semi-quantitative sans paramètres empiriques. La base d'orbitales atomiques pour l'ion central a été systématiquement variée et l'effet de changements symétriques des longueurs de liaison a été aussi examiné. Pour simuler la présence des cations dans la solution et dans le cristal on a fait des calculs dans lesquels la région autour des ligands était rendue plus attractive pour les électrons. Le spectre d'absorption de MnO 4 −1 est interprété à l'aide des prédictions sur les formes des bandes et les énergies de transition.
    Notes: Abstract The electronic structure of the permanganate ion has been investigated, using a semiquantitative LCAO MO method without empirical parameters. The atomic orbital basis set for the central ion has been varied systematically, and the effect of symmetric changes of bond distances has also been examined. In addition, calculations have been performed in which the regions around the ligands have been made more attractive for electrons, to simulate the presence of cations in solution and in the crystalline state. The electronic absorption spectrum of MnO 4 − has been tentatively assigned, on the basis of predicted band shapes and transition energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526064
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic structures of tetrahedral CrO 4 2− , VO 4 3− and TiCl4 (1968)
    Springer
    Theoretical chemistry accounts 11 (1968), S. 26-30 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Elektronenstrukturen der Tetraedersysteme CrO 4 2− , VO 4 3− und TiCl4 werden an Hand halbquantitativer LCAO-MO Rechnungen diskutiert.
    Abstract: Résumé Discussion des structures électroniques des systèmes tétraédriques CrO 4 2− , VO 4 3− et TiCl4 sur la base de calculs semi-quantitatifs LCAO MO.
    Notes: Abstract The electronic structures of the tetrahedral systems CrO 4 2− , VO 4 3− and TiCl4 are discussed on the basis of semiquantitative LCAO MO calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526065
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  • 8
    Electronic Resource
    Electronic Resource
    The ligand field as a pseudo-potential (1974)
    Springer
    Theoretical chemistry accounts 34 (1974), S. 169-174 
    Details
    ISSN: 1432-2234
    Keywords: Group overlap integrals ; Ligand field as pseudo-potential ; Pseudo-Potential, the ligand field as a ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The introduction of a pseudo-potential in crystal field theory is shown to lead to an expression for the orbital splittings which depend upon the squares of the group overlap integrals between the metal and ligand orbitals. A formula is derived whereby the group overlap integral can be directly expressed in terms of the diatomic sigma- and pi-integrals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00578413
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular point group adaptation of spin-free configurations (1982)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 127-148 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Symmetry adaptation of spin-free multishell electron configurations in molecules to general non-Abelian point groups has been carried out. Using the basis spanning the irreducible representation [2N/2-S, 12S, 0n-N/2-S] of the unitary group U(n) as primitives, the Wigner operators for point groups were applied to generate the required basis. In the process it was found that the segments of the Weyl tableaux could be handled individually. Using this and the matric algebra of permutation group a viable procedure has been developed for point groups adaptation. A program based on the procedure has been generated and implemented.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560220113
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