Syntheses and Optical Properties of Azo-Functionalized Ruthenium Alkynyl Complexes

The syntheses of trans-[Ru(CC-1-C6H4-4-N=N-1-C6H4-4-CC-1-C6H4-4-NO2)Cl(L-2)(2)] (L-2=dppm (Ru1), dppe) (Ru2)), trans-[Ru(CC-1-C6H4-4-N=N-1-C6H4-4-(E)-CH=CH-1-C6H4-4-NO2)Cl(dppe)(2)] (Ru3), and trans-[Ru(CC-1-C6H4-4-(E)-CH=CH-1-C6H2-2,6-Et-2-4-N=N-1-C6H4-4-NO2)Cl(dppe)(2)] (Ru4) are reported, together with those of precursor alkynes. Their electrochemical properties were assessed by cyclic voltammetry (CV), linear optical and quadratic nonlinear optical (NLO) properties assayed by UV/Vis-NIR spectroscopy and hyper-Rayleigh scattering studies at 1064nm, respectively, and their linear optical properties in the formally Ru-III state examined by UV/Vis-NIR spectroelectrochemistry. These data were compared to those of analogues with E-ene and yne linkages in place of the azo groups. Computational studies using time-dependent density functional theory were undertaken on model compounds (Ru2-Ru4) to rationalize the optical behaviour of the experimental complexes.