Are donor–acceptor self organised aromatic systems NLO (non-linear optical) active?

Abstract

This contribution to the understanding of non-linear optical (NLO) properties of organic systems is concentrated on donor–acceptor aromatic systems such as [2]catenanes. We report accurate ab initio quantum chemical calculations of the first static hyperpolarizability ( β) of donor–acceptor aromatic systems containing naphthalene and anthracene as electron donors and pyromellitimide and naphthadiimide as electron acceptors. We investigate the NLO effect when the donor acceptor units are not connected through a bridge. In this kind of system the electronic communication between donor and acceptor is solely due to through space charge transfer mechanism. Geometries of all molecular systems were optimised at the Hartree–Fock level with STO-3G minimal basis set and with the 3-21G split valence basis and finally with 6-31G basis set using gaussian 98W. The first static hyperpolarizabilities of these molecular systems were calculated using Hartree–Fock level using 6-31G basis set using gaussian 98W. To understand the possibility of developing these systems as NLO materials we have also calculated the linear and nonlinear optical properties of bridged donor–acceptor systems. The study suggested that these unconnected donor–acceptor systems equivalent to some [2]catenanes reported in literature in general have little influence on the first static hyperpolarizability, however, the linked macro cyclic systems may have potential applications in the development of non-linear optical materials.