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Conformational Dependence of σ‐Electron Delocalization in Linear Chains: Permethylated Oligosilanes
Author(s) -
Bande Annika,
Michl Josef
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901521
Subject(s) - delocalized electron , electron delocalization , electron , chemistry , computational chemistry , physics , quantum mechanics , organic chemistry
The effects of σ‐electron delocalization on optical properties of saturated linear chains of permethylated oligosilanes are strongly conformation dependent. We analyze the origin of the conformational dependence of the energies of molecular orbitals and of electronic excitations in simple intuitively understandable terms by using a first‐order approximation to the Hückel version of the “Ladder C” model. The analysis is supported by comparison with results of numerical calculations from time‐dependent density functional theory, which agree well with experiment. To facilitate the comparison, a simple procedure has been developed that defines the overall and local fractional σ and π characters of a backbone molecular orbital and a fractional overall and local σσ* and σπ* characters of an excited state for any conformation of a linear chain.