SAC and SAC-CI calculations of excitation and circular dichroism spectra of straight-chain and cyclic dichalcogens

Junji Seino, Yasushi Honda, Masahiko Hada, Hiroshi Nakatsuji

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Accurate quantum-chemical calculations of the excitation energies and the rotatory strengths of dichalcogens R-Ch-Ch-R (Ch = S, Se, Te) were carried out with the symmetry adapted cluster (SAC) and SAC-configuration interaction (CI) methods. A series of straight-chain molecules (dihydrogen dichalcogenide, dimethyl dichalcogenide, and (+)-bis(2-methylbutyl) dichalcogenide) and one cyclic molecule (2,3-(R,R)-dichalcogenadecalin) were adopted for comparative analysis. The calculated excitation and circular dichroism (CD) spectra were in good agreement with experimental ones (Laur, P. H. A. In Proceedings of the Third International Symposium on Organic Selenium and Tellurium Compounds; Cagniant, D., Kirsch, G., Eds.; Universite de Metz: Metz, 1979; pp 219-299) within 0.3 eV. The fitting CD spectra also reasonably reproduced the experimental ones. In all the molecules adopted, the first and second lowest bands were assigned to the n-σ*(Ch-Ch) transition and the third and fourth lowest bands to the n-σ*(Ch-R) transition. The first and second lowest bands apparently depended on the R-Ch-Ch-R dihedral angle, suggesting that the orbital energies of two σ*(Ch-Ch) change with the R-Ch-Ch-R dihedral angle. This calculated trend agrees with two empirical rules: the C2 rule and the quadrant rule.

Original languageEnglish
Pages (from-to)10053-10062
Number of pages10
JournalJournal of Physical Chemistry A
Issue number33
Publication statusPublished - 2006 Aug 24
Externally publishedYes


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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