Photophysical and Photochemical Properties of Three-Dimensional Metal-Tris-Oxalate Network Structures

Abstract

Chemical variation and combination of metal ions of different valencies in the oxalate backbone as well as in the tris-bpy cation of the three-dimensional network structures of the type [M^II ₂(ox)₃][M^II(bpy)₃] (bpy = 2,2′-bipyridine, ox = C₂O₄ ^2-), [M^IM^III(ox)₃][M^II(bpy)3] and [M^IM^III(ox)3][M^III(bpy)3]ClO₄ offer unique opportunities for studying a large variety of photophysical processes. Depending upon the relative energies of the excited states of the chromophores, excitation energy transfer either from the tris-bipyridine cation to the oxalate backbone or vice versa is observed, as for instance from [Ru(bpy)₃]²⁺ as photo-sensitiser to [Cr(ox)₃]^3- as energy acceptor in the combination [NaCr(ox)₃][Ru(bpy)₃], or from [Cr(ox)₃]^3- to [Cr(bpy)₃]³⁺ in [NaCr(ox)₃][Cr(bpy)₃]ClO₄. In addition efficient energy migration within the oxalate backbone is observed. Furthermore, depending upon the excited state redox potentials, light-induced electron transfer processes may be envisaged.