Organometallic complexes for nonlinear optics. Part 36. Quadratic and cubic optical nonlinearities of 4-fluorophenylethynyl- and 4-nitro-( E )-stilbenylethynylruthenium complexes

Abstract

The complexes trans-[Ru(CC-4-C6H4F)X(dppe) 2] [X = Cl (1), CCPh (2), CC-4-C6H4NO 2 (3)], trans-[Ru{CC-4-C6H4-(E)-CHCH-4-C 6H4NO2}X(dppe)2] [X = CCPh (4), CC-4-C6H4CCPh (5)], and [C6H 3-1,3-{CC-trans-[RuCl(dppe)2]}2-5-(CC-4-C 6H4F)] (6) have been synthesized and the identity of 1 confirmed by a single-crystal X-ray diffraction study. Cyclic voltammetry reveals a metal-centered oxidation, the potential of which is largely invariant on alkynyl ligand replacement across the series 1-5; the diruthenium complex 6 shows two oxidation processes, consistent with weakly interacting metal centers. Hyper-Rayleigh scattering (HRS) studies at 1064 nm using ns pulses suggest quadratic nonlinearities for 3-5 that are amongst the largest thus far for organometallic complexes, a trend maintained with the two-level-corrected data. HRS studies at 800 nm using fs pulses and amplitude modulation to remove multi-photon fluorescence contributions reveal significant fluorescence-free nonlinearities for 3-5; the frequency-independent nonlinearities calculated from the 800 nm results are suggestive of fluorescence contributions to the 1064 nm data. Z-scan studies at 820 nm reveal cubic nonlinearities that increase with the size of the π-system, although error margins are significant. Show more