CHIRAL METAL-COMPLEXES WITH LARGE OCTUPOLAR OPTICAL NONLINEARITIES

OPTICALLY nonlinear organic materials show considerable potential for applications in optical signal processing and telecommunications(1,2). Most materials are based on the p-nitroaniline template, in which the optical nonlinearities are intimately associated with quasi-one-dimen sional charge transfer. But there are problems associated with this co nventional approach, arising from the strongly dipolar nature of the m olecules(2). It has recently been recognized(3-5) that two- and three- dimensional stereochemistry offers new possibilities for the design an d synthesis of optically nonlinear molecules, in which charge transfer is multidirectional rather than dipolar in character; octupolar nonli nearities have now been demonstrated in several molecular systems(5-7) . Tri-substituted ruthenium complexes(6) appear particularly attractiv e because intense, multidirectional metal-to-ligand charge transfer le ads to a significant enhancement of the optical nonlinearity, as quant ified by the quadratic hyperpolarizability, beta. Here we show that th e choice of ligand can further increase beta to values in excess of 10 (-27) e.s.u., comparable to the best dipolar optically nonlinear molec ules.