Geometric and electronic structure and nonlinear optical properties of push-push and pull-pull conjugated systems

We present ab initio coupled perturbed Hartree-Fock (CPHF) calculations on the first-order polarizabilities of phenylene and hexatriene conjugated segments end-capped by either two push (electron donor) groups, two pull (electron acceptor) groups, or one push and one pull groups. The push groups are taken to be amine functionalities, the pull groups are nitro or aldehyde functionalities. The results obtained at the split-valence basis set, without and with polarization functions, indicate that while the α values differ by only a factor of two, the γ values are scattered over two orders of magnitude. The largest values of γ are provided by the push-pull compounds.