Organometallic complexes for nonlinear optics: Part 25. Quadratic and cubic hyperpolarizabilities of some dipolar and quadrupolar gold and ruthenium complexes

The complexes [Au(4-CCC6H4NO2)(L)] [L=PCy3 (1), PMe3 (2)], [(L)Au(μ-4-CCRCC)Au(L)] [R=C6H4, L=PCy3 (4), PPh3 (5); R=C6H4-4-C6H4, L=PCy3 (7), PPh3 (8)], trans,trans-[RuCl(dppm)2(μ-4,4′-CCC6H4C6H4CC)RuCl(dppm)2] (11), trans-[Ru(X)(Y)(dppe)2] [X=Cl, Y=4-CCC6H4I (12), 4-CCC6H4CCSiMe3 (13); X=CCPh, 4-CCC6H4CCH (14)] and {trans-[Ru(CCPh)(dppe)2]}2(μ-4,4′-CCC6H4CCCCC6H4CC) (15) have been prepared and their electrochemical (Ru complexes) and nonlinear optical properties assessed. Electronic communication between the metal centers in 10, 11 and 15 diminishes as the π-delocalizable bridge is lengthened. Quadratic nonlinear optical (NLO) merit increases on replacing triarylphosphine by trialkylphosphine, the relative β values Au(4-CCC6H4NO2)(PPh3)<1<3 being observed. Cubic NLO values are small for the gold complexes and much larger for the ruthenium examples. Complex 15 has the largest σ2/MWt (two-photon absorption cross-section/molecular weight) value observed thus far for an organometallic complex.