Hyperpolarisability - Molecular twist correlation in diaminodicyanoquinodimethanes

Abstract

Semiempirical quantum chemical calculations are carried out on the class of diaminodicyanoquinodimethanes. The calculated first hyperpolarisabilities of these molecules manifest a close correlation with the twist angle between the diaminomethylene unit and the aromatic ring. The correlation follows earlier model calculations on a prototypical molecule and can be qualitatively explained on the basis of the well-known two-level approximation.