Turning Off Phototriggered Linkage Isomerizations in Ruthenium Dimethyl Sulfoxide Complexes

We report on the spectroscopy, electrochemistry, and linkage isomerization in a family of [Ru(tpy)(L2)(dmso)]z+ complexes (tpy is 2,2ʹ:6ʹ,2ʹ ʹ-terpyridine, dmso is dimethyl sulfoxide, and L2 is a variable ligand: 2,2ʹ-bipyridine (bpy), 2-picolinate (pic), N,N,Nʹ,Nʹtetramethylethylenediamine (tmen), acetylacetonate (acac), or malonate (mal)). The identity of this bidentate ligand serves to tune the absorption maxima ((lambda)max = 419-502 nm) and the reduction potential (E1/2 = 1.67 to 0.82 V) of these complexes. Photochemical and electrochemical studies show that S(right arrow)O and O(right arrow)S linkage isomerization may be triggered through an electron transfer mechanism, resulting in dramatic shifts in both the absorption maxima and the reduction potential (for [Ru(tpy)(pic)(dmso)]+ Sbonded, 421 nm, 1.38 V vs Ag/AgCl; O-bonded, 527 nm, 1.38 V vs Ag/AgCl). Certain of these complexes [Ru(tpy)(acac)(dmso)]+ and [Ru(tpy)(mal)(dmso)] do not undergo isomerization. These results are discussed in the context of electron transfer triggered isomerization.