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Electronic structure of. pi. systems. II. Photoelectron spectra and occupied orbitals of some. pi. donors which are derivatives and analogs of bipyranylidene

Journal Article · · J. Gen. Chem. USSR (Engl. Transl.); (United States)
OSTI ID:5646790
Quantum-chemical calculations by a simple method (parametrization based on data from photoelectron spectroscopy) objectively reproduce the structure of the occupied ..pi.. molecular orbitals of ..pi.. donors of the bichalcogenapyranylidene and tetrachalcogenafulvalene series. The occupied ..pi.. molecular orbitals of the bichalcogenapyranylidenes have the same order as do the orbitals of the tetrachalcogenafulvalenes, but they have smaller contributions from the AO's of the heteroatoms: 3b/sub 1u/, 2b/sub 2g/, 1a/sub 1u/, 1b/sub 3g/, 2b/sub 1u/, 1b/sub 2g/, 1b/sub 1u/. The first ionization potentials of the bichalcogenapoyranylidenes are somewhat lower than those of the analogous tetrachalcogenafulvalenes, but the second ionization potentials are considerably higher. As the atomic number of the chalcogen is increased, the occupied molecular orbitals approach each other to an appreciable extent in the series of bichalcogenapyranylidenes. In tetraphenylbichalcogenapyranylidenes there are electronic levels which are delocalized over the entire molecule.
Research Organization:
D. I. Mendeleev Moscow Chemical-Engineering Institute, USSR
OSTI ID:
5646790
Journal Information:
J. Gen. Chem. USSR (Engl. Transl.); (United States), Journal Name: J. Gen. Chem. USSR (Engl. Transl.); (United States) Vol. 57:3; ISSN JGCHA
Country of Publication:
United States
Language:
English