Tris(4,4′-dimethoxy-2,2′-bipyridine)osmium(II), amperometric properties and crystal structure

The complex cation [Os(DMO-bpy)(3)](2+) (DMO-bpy = 4,4'-dimethoxy-2,2'-bipyridine) was prepared as Cl- and PF6- salts. Using cyclic voltammetry, the system (glucose oxidase + [Os(DMO-bpy)(3)]Cl-2 on graphite electrode), closely approaching the biosensor, was examined. The crystal structure of [Os(DMO-bpy)(3)] (PF6)(2), solvate with dimethylformamide, was determined at 293 K. The crystals are triclinic, a = 11.634(3), b = 13.375(6), c = 15.113(7) Angstrom, alpha = 76.95(4)degrees, beta = 84.29(3)degrees, gamma = 79.67(3)degrees, space group P1, Z = 2, R = 0.086 for 3628 reflections. The average Os-N distance of 2.052 Angstrom agrees with the value observed in other bpy complexes of Os(II). The N(metal)N bond angles and dihedral angles between the bpy ligands are less distorted as in the crystal of the isostructural Fe(II) complex with smaller Fe-N separations of 1.967 Angstrom. The terminal C atoms of CH3O-substituents are coplanar with the planes of corresponding bpy ligands but the orientations of the vectors of the C-O bonds are different. The slight increase in intermolecular contacts and metal...metal separations when going from the Fe(II) to the Os(II) structure may be explained also by exchange of the N-methyl-2-pyrrolidone solvate molecule in the Fe(II) structure for dimethylformamide in the Os(II) structure. The relation between the molecular geometry of the complex and possible types of interaction of the complex with the glucose oxidase surface is discussed. (C) 1998 Elsevier Science S.A. All rights reserved.