4,4′-Dihydroxy-2,2′-bipyridine complexes of Co(III), Cu(II) and Zn(II); structural and spectroscopic characterization

New Co(III), Cu(II) and Zn(II) complexes of 4,4′-dihydroxy-2,2′-bipyridine (dhbpyH2) have been structurally characterized by single crystal X-ray diffraction methods and studied by electrochemical and spectroscopic techniques. Both bis- and tris-dhbpyH2 zinc complexes were characterized in solution and solid state. A rare case of accidental isochronism of the H5 and H6 protons was identified in the 1H NMR spectrum of the Co(III) complex. The cobalt and copper complexes show reversible one-electron electrochemical reductions. Luminescent emission with a life time t = 4.95 ns was recorded for [Zn(dhbpyH2)2]2+ upon UV irradiation.