The complexes trans-[Ru(CC-4-C 6 H 4 F)X(dppe) 2 ] [X=Cl (1), CCPh (2), CC-4-C 6 H 4 NO 2 (3)], trans-[Ru{CC-4-C 6 H 4 -(E)-CHCH-4-C 6 H 4 NO 2 }X(dppe) 2 ] [X=CCPh (4), CC-4-C 6 H 4 CCPh (5)], and [C 6 H 3 -1,3-{CC-trans-[RuCl(dppe) 2 ]} 2 -5-(CC-4-C 6 H 4 F)] (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 1064nm 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 800nm 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 800nm results are suggestive of fluorescence contributions to the 1064nm data. Z-scan studies at 820nm reveal cubic nonlinearities that increase with the size of the π-system, although error margins are significant.