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

The complexes trans-[Ru(CC-4-C6H4F)X(dppe)2] [X = Cl (1), CCPh (2), CC-4-C6H4NO2 (3)], trans-[Ru{CC-4-C6H4-(E)-CHCH-4-C6H4NO2}X(dppe)2] [X = CCPh (4), CC-4-C6H4CCPh (5)], and [C6H3-1,3-{CC-trans-[RuCl(dppe)2]}2-5-(CC-4-C6H4F)] (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.

Hyper-Rayleigh scattering (HRS) studies of ruthenium complexes with 4-fluorophenylethynyl or 4-nitro-(E)-stilbenylethynyl ligands at 1064 nm using ns pulses suggest quadratic nonlinearities for the nitrostilbenyl complexes are amongst the largest thus far for organometallic complexes, while HRS studies at 800 nm using fs pulses and amplitude modulation to remove multi-photon fluorescence contributions reveal significant fluorescence-free nonlinearities. Z-scan studies at 820 nm reveal cubic nonlinearities of these complexes increase with the size of the π-system.Figure optionsDownload as PowerPoint slide