Syntheses and Optical Properties of Azo‐Functionalized Ruthenium Alkynyl Complexes

The syntheses of trans ‐[Ru(C≡C‐1‐C 6 H 4 ‐4‐N=N‐1‐C 6 H 4 ‐4‐C≡C‐1‐C 6 H 4 ‐4‐NO 2 )Cl(L 2 ) 2 ] (L 2 =dppm ( Ru1 ), dppe) ( Ru2 )), trans ‐[Ru(C≡C‐1‐C 6 H 4 ‐4‐N=N‐1‐C 6 H 4 ‐4‐( E )‐CH=CH‐1‐C 6 H 4 ‐4‐NO 2 )Cl(dppe) 2 ] ( Ru3 ), and trans ‐[Ru(C≡C‐1‐C 6 H 4 ‐4‐( E )‐CH=CH‐1‐C 6 H 2 ‐2,6‐Et 2 ‐4‐N=N‐1‐C 6 H 4 ‐4‐NO 2 )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 1064 nm, 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.