Electronic perturbation effects in the presence of electric field for π-conjugated systems: An electron-correlation study

In this work, the Coulson-Longuet-Higgins response function (atom-atomic polarizabilities [AAPs]) is used to describe the transfer of an electron perturbation in π-conjugated systems in the presence of a static electric field. Computations are performed using different many-electron approaches to study the effect. An accurate account of the electron correlation is shown to play a key role in the description of the interaction of a π-shell with the external electrostatic field. Studies in this work reveal that the Hückel theory widely used in calculations of electron-perturbation transfer is not reliable even at the qualitative level to describe the effects studies in this work. However, the π-electron coupled cluster theory has been proven capable of providing a reliable electronic structure (among them, AAPs and excitation energies) that agree with the results obtained with the π-electron full configuration-interaction approach. The calculations also show that these properties have an essentially nonlinear character in terms of the strength of the applied electric field. The results obtained in the present work can provide useful information relevant to the application of π-conjugated systems in molecular electronics.