Dipole moments of polyenic oligomeric systems. Part I. A One-dimensional molecular wire model

Ground-state dipolar moments of oligomeric compounds, containing electron-donor (D) and electron-acceptor (A) groups as two terminal units of the polyenic bridge (D-wire-A), can well be described by means of a one-dimensional molecular wire model, which considers a scattering process of electrons through the charge-transfer conduction channel. The dipole moment of the oligomers (μ_n) follows a non-linear dependence of the polyenic bridge length (L) according to μ_n = μ₀ + μ_∞ (1 - e^-γL) where μ₀ is the dipole moment of the first compound of the series, without a polyenic unit (n = 0), μ_∞ is a limit value for L → » ∞ and γ is the one-dimensional conduction constant of the π-molecular orbital channel of the molecular wire. This model can be extended to all those conjugated oligomers of the D-wire-A type where the electronic charge of the donor group can induce a soliton wave as far as through the polyenic bridge towards the acceptor group.