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(2)(II)(ox)(3)][M(II)(bpy)(3)] (bpy = 2,2’-bipyridine, ox = C2O42-), [M(I)M(III)(ox>(3)][M(II)(bpy)(3)] and [M(I)M(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.