CIS-BIS(BIPYRIDINE)RUTHENIUM IMIDAZOLE DERIVATIVES - A SPECTROSCOPIC,KINETIC, AND STRUCTURAL STUDY

The ruthenium bis(bipyridine) complexes cis-[Ru(bpy)(2)Im(OH2)](2+), c is-[Ru(bpy)(2)(Im)(2)](2+), cis-[Ru(bpy)(2)(N-Im)(2)](2+), cis-[Ru(dmb py)(2)Im(OH2)](2+), cis-[Ru(dmbpy)(2)(N-Im)(OH2)](2+)(bpy = 2,2'-bipyr idine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, Im = imidazole, N-Im = N -methylimidazole), have been synthesized under ambient conditions in a queous solution (pH 7). Their electrochemical and spectroscopic proper ties, absorption, emission, and lifetimes were determined and compared . The substitution kinetics of the cis-[Ru(bpy)(2)Im(OH2)](2+) complex es show slower rates and have lower affinities for imidazole ligands t han the corresponding cis-[Ru(NH3)(4)Im(OH2)](2+) complexes. The cryst al structures of the monoclinic cis-[Ru(bpy)(2)(Im)(2)](BF4)(2), space group = P2(1)/a, Z = 4, a = 11.344(1) Angstrom, b = 17.499(3) Angstro m, c = 15.114(3) Angstrom, and beta = 100.17(1)degrees, and triclinic cis-[Ru(bpy)(2)(N-Im)(H2O)](CF3COO)(2) . H2O, space group = P (1) over bar, Z = 2, a = 10.432(4) Angstrom, b = 11.995(3) Angstrom, c = 13.91 2(5) Angstrom, alpha = 87.03(3)degrees, beta = 70.28(3)degrees, and ga mma = 71.57(2)degrees, complexes show that these molecules crystallize as complexes of octahedral Ru(II) to two bidentate bipyridine ligands with two imidazole ligands or a water and an N-methylimidazole ligand cis to each other. The importance of these molecules is associated wi th their frequent use in the modification of proteins at histidine res idues and in comparisons of the modified protein derivatives with thes e small molecule analogs.