New luminescent isomeric europium(III) complexes with carboxylic carbonyl group coordination (I and II) have been prepared by solvothermal synthesis using the ligand 2,2 '-bipyridine-4,4 '-dicarboxylic acid (bpdc), with the nonradiatively shielded Eu3+ coordination sphere completed by dimethyl sulfoxide ligands. The room temperature IR spectra and Eu3+ luminescence spectra do not provide a definitive distinction between I and II, but low-temperature luminescence can give a clear identification.