Publication 875

University of Torino, Department of Chemistry, via P. Giuria 7, 10125 Torino, Italy
Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d’Electrochimie Moléculaire, UMR 7591 CNRS, 15 rue Jean-Antoine de Baïf, Paris Cedex 13 F-75205, France
The Czech Academy of Sciences, J. Heyrovský Institute of Physical Chemistry, Dolejškova 3, 18223 Prague, Czech Republica

The novel rhenium complexes fac-Re(pdbpy)(CO)₃Cl (pdbpy = 4-phenyl-6-(phenyl-2,6-diol)-2,2'-bipyridine), 1, and fac-Re(ptbpy)(CO)₃Cl (ptbpy = 4-phenyl-6-(phenyl-3,4,5-triol)-2,2'-bipyridine), 2, have been synthesized, and the single crystal X-ray diffraction (SC-XRD) structure of 1 was solved. The electrochemical behaviors of the complexes in acetonitrile under Ar and their catalytic performances for CO₂ reduction with added water and MeOH are discussed. A detailed IR spectroelectrochemical study under Ar and CO₂ atmospheres coupled with DFT calculations allows the identification of reduced species and the interpretation of the reduction mechanisms. Comparison between the rhenium complexes and the corresponding Mn derivatives Mn(pdbpy)(CO)₃Br, 3, and Mn(ptbpy)(CO)₃Br, 4, has been also considered. Finally, photostimulated conversion of the CO₂ was investigated with catalysts (1, 3, and 4) under visible light irradiation (lambda > 420 nm) in acetonitrile as solvent. Remarkably, 1 and 3 catalysts were active toward CO₂, producing formate with good selectivity and turnover number (TON). For example, 3 gives 62% selectivity for HCOO^-- and a TON of 80, and Re compound 1 gives 74% selectivity for HCOO^- and a TON of 86.