Electrocatalytic Reduction Of Protons To Hydrogen By A Copper Complex Of The Pentadentate Ligand Dmphen-Dpa In A Nonaqueous Electrolyte

A copper complex based on the pentadentate aminopyridine ligand [(9-methyl-1,10-phenanthrolin-2-yl)methyl]bis-(pyridin-2-ylmethyl)amine (Dmphen-DPA), namely [Cu(Dmphen-DPA)](ClO4)(2) (1), was synthesized and characterized by elemental analysis, HR-MS spectroscopy and X-ray single crystal diffraction. The complex has five-coordinated solid-state structures, but has an open coordination site in acetonitrile. The electrochemical studies reveal that complex 1 has an electrocatalytic proton reduction activity in acetonitrile, when using acetic acid as a proton source with i(cat)/i(p) similar to 2.5. DFT calculations suggest that the parent copper complex undergoes two successive reductions to generate the radical species [Cu(i)(Dmphen-DPA(-))](0), which is protonated at the low-valence copper center to afford a reactive Cu-II-H intermediate. The Cu-II-H species combines bimolecularly and generates H(2)via reductive elimination.