Effect of Conformation on Electron Localization and Delocalization in Infinite Helical Chains [X(CH3)2]∞ (X = Si, Ge, Sn, and Pb).
J Am Chem Soc
; 141(33): 13101-13113, 2019 08 21.
Article
em En
| MEDLINE
| ID: mdl-31306578
ABSTRACT
An intuitive explanation of the effects of conformation (backbone dihedral angle) on electron delocalization in infinite saturated regular helices [(CH3)2]∞Si, [(CH3)2Ge]∞, [(CH3)2Sn]∞, and [(CH3)2Pb]∞ is offered in terms of the simple Ladder C model and confirmed by density functional theory calculations. The effective hole mass, which ranges from near zero to infinity as a function of conformation, is used as a measure of the degree of delocalization and relates to the effects of chain length extension in finite systems. The position of the Fermi level in reciprocal space has a simple counterpart in systems of finite length and is used to characterize the dominant mechanism, σ conjugation (geminal interactions) or σ hyperconjugation (vicinal interactions, through-bond coupling). Constructive or destructive interference of the two mechanisms produces three different delocalization regimes as a function of the backbone dihedral angle and analogy is drawn to polycyclic π-electron systems consisting of fused Hückel or Möbius four-membered rings.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article