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

Abstract

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 π-delocalized terpyridine moieties bearing a D and an A group, respectively, leading to a large quadratic hyperpolarizability hugely dominated by the octupolar contribution.