The three new mono- and dimetallic tricarbonyl manganese(I) complexes with iminopyridine ligand based on acenaphthene have been prepared. The potential of complexes as catalysts for CO₂ reduction reaction and hydrogen evolution reaction was investigated. It was found that the monometallic complex has an advantage over the dimetallic complex, which is manifested by a higher catalytic performance.

Abstract

The present study reports the synthesis and structural characterization of two novel mono- and dimetallic tricarbonyl manganese(I) complexes with an acenaphthene-based iminopyridine ligand. The investigation revealed that ligand-centered reduction occurred for the monometallic complex, while Mn-centered reduction was observed for the dimetallic complex, both at the first reduction peak potentials. This determination was made through a combination of cyclic voltammetry, bulk electrolysis, and electron paramagnetic resonance spectroscopy. The study further explores the ability of both complexes as catalysts for the CO₂ reduction reaction (CO₂RR) and hydrogen evolution reaction (HER). The monometallic complex exhibited a 400-mV gain in overpotential and an 80 to 12 turnover number (TON) advantage over the dimetallic complex for CO₂RR, with 2,2,2-trifluoroethanol serving as the proton source. The monometallic Mn^I complex demonstrates notable stability in acidic media, exhibiting a high turnover frequency of 2400 s⁻¹ and a TON of 450 in HER.