SPECTROSCOPIC AND ELECTROCHEMICAL STUDIES OF A SERIES OF COPPER(I) AND RHENIUM(I) COMPLEXES WITH SUBSTITUTED DIPYRIDO[3,2-A-2',3'-C]PHENAZINE LIGANDS

Copper(I) and rhenium(I) complexes with the ligand dipyrido[3,2,-a:2', 3'-c]phenazine (dppz) and a number of substituted analogues have been synthesized. Their spectroscopic and electrochemical properties have b een studied. It is found that the lowest-energy transition for the com plexes is metal-to-ligand charge transfer (MLCT) in nature. This has a low epsilon value. The resonance Raman spectra for the complexes show groups of bands that shift with substitution at the ligand and groups that remain unchanged in wavenumber. Electrochemical reduction of the complexes resulted in the formation of the ligand radical anion speci es for all but one system. This was confirmed by UV/VIS spectroelectro chemistry. Using resonance Raman spectroelectrochemistry marker bands have been identified for the radical anion species. The excited states of the complexes were studied by excited-state electronic absorption and time-resolved resonance Raman techniques. The former spectra are a mbiguous as to the nature of the lowest excited state; however, the la tter spectra confirm that this state is ligand-centred for complexes o f dppz and its 11-methyl derivative. Complexes with the 11-nitro deriv ative appear to form excited states that are MLCT in nature.