Octupolar metal complexes for quadratic nonlinear optics

The classical molecular engineering schemes based on quasi one-dimensional dipolar charge transfer are enlarged to molecules with two- or three-dimensional contributions of octupolar origin. We report here a large increase in quadratic hyperpolarizability /spl beta/ values (up to 2.10/sup -27/ e.s.u.) of chiral ruthenium complexes upon successive complexation by one, two and three bipyridine derivatives. A strong metal-to-ligand charge transfer is evidenced from comparison of the experimental /spl beta/ value of the three-substituted complex with that deduced from a simple additive model of metal-ligand interaction.