Molecular resistivities in organic polyenic wires - I. A one-dimensional photoconduction charge transfer model

In the present work we have developed a one-dimensional photoconduction cha rge transfer model, which allows us to determine the resistivities associat ed to pi-conduction molecular channels of organic polyenic wires. In order to calculate the charge transmission coefficient through the conductor mole cular wire, our model is based on the scattering process of electrons in me tals according to Landauer's one-dimensional conductor approach. This model can be applied to those D-bridge-A molecular systems, constituted by an el ectron-donor group (D), an electron-acceptor group (A) and a polyenic condu ctor molecular bridge, which present a photoinduced charge transfer absorpt ion band. According to the present model, molecular resistivities and resis tances in the charge transfer excited state of a series of polyenic compoun ds containing several kinds of electron-donor groups and CO, as an electron -acceptor group, have been calculated by means of the INDO/S-CI method, in the framework of ZINDO semiempirical molecular orbital theory. The calculat ions allow us to determine the linear and nonlinear contributions to the to tal molecular resistance of the pi-conduction channel in the charge transfe r excited state. Linear resistivities for a series of polyenic aldehydes su bstituted by an electron-donor group (D = -CH3, -OCH3, -NH2 and -N[CH3](2)) range between 18 and 42 mu Ohm cm and these results agree with the order o f magnitude expected in classic conductors such as metals, nonmetals, and d oped polyacetylenic compounds in the ground state. (C) 1999 Elsevier Scienc e B.V. All rights reserved.