New [(D-terpyridine)-Ru-(D or A-terpyridine)][4-EtPhCO2]2 complexes (D = electron donor group; A = electron acceptor group) as active second-order non linear optical chromophores

The dipolar and octupolar contributions of the second order nonlinear optical properties of [(4?-(C6H4 - p-D)-2,2?:6?,2??-terpyridine)-Ru-(4?-(C6H4 -p-A)-2,2?:6?,2??-terpyridine)]Y2 heteroleptic complexes (D and A are donor and acceptor groups, respectively), and related free terpyridines and homoleptic complexes, have been obtained by means of a comprehensive combination of Electric Field Induced Second Harmonic generation, Third Harmonic Generation, and Harmonic Light Scattering measurements. These results evidence how a metal can act as a bridge between two ?-delocalized terpyridine moieties bearing a D and an A group, respectively, leading to a large quadratic hyperpolarizability hugely dominated by the octupolar contribution.