Electrochemical and spectroelectrochemical studies of complexes of 1,10-phenanthroline-5,6-dione

► Redox studies of 1,10-phenanthroline-5,6-dione and its Pt, Pd and Ru complexes. ► N,N′-bound complexes undergo facile reversible one-electron reduction. ► O,O′-bound complex has reversible one-electron oxidation at low temperature. ► EPR, UV-Vis and DFT results indicate CO groups electronically important.