Theoretica chimica acta

, Volume 26, Issue 2, pp 131–140 | Cite as

The use of the CNDO method in spectroscopy

VI. further n — π* transitions
  • R. L. Ellis
  • G. Kuehnlenz
  • H. H. Jaffé
Commentationes

Abstract

The Pariser approximation for the two center Coulomb repulsion integrals Γrshas been replaced by the Nishimoto-Mataga approximation in the original CNDO/S method. This modification has significantly improved the calculated position of the benzene 1B1u1A1g(1La) electronic transition in benzenoid compounds. The calculation of transition moments of n — π* transitions is also considered. These moments vanish formally in any theory employing the ZDO approximation since integrals of the form 〈2s¦er2p〉 vanish even when the 2s and 2p atomic orbitals are on the same center. In this work the ZDO approximation is abandoned in the evaluation of the electronic transition moment resulting in calculated intensities for n — π*, 1W←1A, transitions which are in good agreement with experiment.

Zusammenfassung

Die Näherung für die Zweizentrencoulombintegrale nach Pariser in der ursprünglichen Form des CNDO/S-Verfahrens wurde durch die von Nishimoto-Mataga ersetzt, wodurch sich der 1B1u1A1g(1La)-Übergang in benzoiden Verbindungen besser ergibt. Die n — π*-Übergangsmomente, die bei ZDO-Annahme immer verschwinden, weil dann 〈2s¦er¦2p〉 auch für an gleichen Zentren liegende Orbitale Null ist, werden hier berechnet, und zwar für den 1W1A-Übergang, wobei die Übereinstimmung mit dem Experiment befriedigend ausfällt.

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Copyright information

© Springer-Verlag 1972

Authors and Affiliations

  • R. L. Ellis
    • 1
  • G. Kuehnlenz
    • 1
  • H. H. Jaffé
    • 1
    • 2
  1. 1.Department of ChemistryUniversity of CincinnatiCincinnatiUSA
  2. 2.Centre de Méchanique Ondulaire Appliquée 23Paris XIXFrance

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