Photochemical isomerization of trans- to cis-[RuCl2(dppb) (4,4′-X2-2,2′-bipy)] (X = -H, -NO2, -Me, -COOH, -SMe, -O=SMe, -Cl, -OMe) complexes

Article abstract of DOI:10.1016/j.poly.2003.07.007

A series of [RuCl₂(dppb)(4,4′-X₂-2,2′ -bipy)] complexes was synthesized from [RuCl₂(dppb)(PPh₃) and 4,4′-X₂-2,2′-bipy [dppb=1,4-bis(diphenylphosphino)butane and 4,4′-X₂-2,2′ -bipy=2,2′-bipyridine (bipy), 4,4′-dimethoxy-2,2′-bipyridine (MeO-bipy), 4,4′-dimethyl-2,2′-bipyridine (Me-bipy), 4,4′-dicarboxy-2,2′-bipyridine (COOH-bipy), 4,4′ -dithiomethyl-2,2′-bipyridine (MeS-bipy), 4,4′-dichloro-2,2′ -bipyridine (Cl-bipy), 4,4′-dinitro-2,2′-bipyridine (NO ₂-bipy), and 4,4′-dithiomethylsulphoxide-2, 2′-bipyridine (MeS=O-bipy)]. The complexes were characterized by elemental analysis, cyclic voltammetry and differential pulse voltammetry, and by UV-Vis and ³¹P{¹H}NMR spectroscopies. The pK _a of the ligands were determined. The trans-[RuCl ₂(dppb)(4,4′-X₂-2,2′-bipy) complexes were photoisomerized under white light and the isomerization rate constants from trans to cis isomers were consistent with first order reactions and were correlated with the pK_a of the ligands and with the E_1/2 of the complexes. The suggested mechanism of isomerization reactions is consistent with an intramolecular twist process.