Conformational Dependence of σ-Electron Delocalization in Linear Chains: Permethylated Oligosilanes
✍ Scribed by Annika Bande; Josef Michl
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 908 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
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.