The coordination chemistry of dipyrrolic heme metabolites, referred to as propentdyopents, has been investigated with several late transition metals (Co, Ni, Cu and Zn). The crystal structures of these complexes present pseudo-tetrahedral geometries, in which each metal center is bound to two monoanionic bidentate ligands in a 1:2 binding mode. The electrochemical analysis of homoleptic propentdyopent complexes confirms the presence of two quasi-reversible one-electron redox events, which were assigned to the ligand systems. Indeed, the successive reduction of each propentdyopent ligand can be monitored by controlled potential electrolysis and simultaneously by UV-visible absorption spectroscopy. These reductions lead to the appearance of new low-energy bands, in the (670-750) nm range, which are characteristic of oligopyrrolic π radicals.  The resulting species are also accessible by chemical reduction and can be characterized by electron paramagnetic resonance (EPR) spectroscopy. This study demonstrates that propentdyopent ligands can serve as electron reservoirs in transition metal complexes and provide a platform for reversible ligand-based redox chemistry.<br/><br/>

Formation of radical anions on the dipyrrin-1,9-dione scaffold of heme metabolites

253rd National Meeting (2017)

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