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

Ground-state dipolar moments of oligomeric compounds, containing electron-d onor (D) and electron-acceptor (A) groups as two terminal units of the poly enic bridge (D-wire-A), can well be described by means of a one-dimensional molecular wire model, which considers a scattering process of electrons th rough the charge-transfer conduction channel. The dipole moment of the olig omers (mu(n)) follows a non-linear dependence of the polyenic bridge length (L) according to mu(n), = mu(0) + mu(infinity) (1 - e(-gamma L)) where mu( 0) is the dipole moment of the first compound of the series, without a poly enic unit (n = 0), mu(infinity) is a limit value fort L --> infinity and ga mma is the one-dimensional conduction constant of the pi-molecular orbital channel of the molecular wire. This model can be extended to all those conj ugated oligomers of the D-wire-A type where the electronic charge of the do nor group can induce a soliton wave as far as through the polyenic bridge t owards the acceptor group. (C) 1998 John Wiley & Sons, Ltd.