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Photochemical CO 2 Reduction Using Rhenium(I) Tricarbonyl Complexes with Bipyridyl‐Type Ligands with and without Second Coordination Sphere Effects
Author(s) -
Rotundo Laura,
Grills David C.,
Gobetto Roberto,
Priola Emanuele,
Nervi Carlo,
Polyansky Dmitry E.,
Fujita Etsuko
Publication year - 2021
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.202000307
Subject(s) - chemistry , moiety , photochemistry , ligand (biochemistry) , coordination sphere , deprotonation , rhenium , medicinal chemistry , metal , inorganic chemistry , stereochemistry , organic chemistry , ion , biochemistry , receptor
The effect of phenyl, phenol, aniline, amino, and CF 3 substituents of the 2,2′‐bipyridine ligand in fac ‐ReCl(L)(CO) 3 (L=2,2′‐bipyridine derivative) catalysts on photochemical CO 2 reduction in dimethylacetamide is examined, in order to understand the structure‐function relationships and to compare the catalytic activities with the previously published electrochemical results. All complexes including ReCl(bpy)(CO) 3 have similar excited‐state lifetimes and emission spectra, but complex 1 with the Ph‐NH 2 moiety exhibits a significantly larger molar absorption coefficient for its metal‐to‐ligand charge transfer (MLCT) band. All complexes we tested produce CO with only a negligible amount of H 2 and formate in self‐sensitized systems in the presence of triethanolamine (TEOA) and in some cases, BIH (1,3‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐benzo[ d ]‐imidazole). The presence of the Ph‐NH 2 moiety (complex 1 ) has a beneficial effect on both electrochemical and photochemical activity, allowing a turnover number (TON) of 32 and 120 for photochemical CO production (without and with BIH, respectively). In the case of the Ph‐OH group in the second coordination sphere (complexes 4 and 6 ), these complexes are active for photochemical CO 2 reduction, despite the formation of a stable 6‐coordinate Re‐OPh intermediate via reductive deprotonation as previously observed under electrochemical conditions. Overall, BIH accelerates the rate of formation of the one‐electron reduced species (OERS) of the Re catalysts and allows higher turnover frequency (TOF) and TON for CO formation. The X‐ray structures of complexes 1 and 4 were determined to have distorted octahedral Re centres, and show π‐π stacking interactions with neighboring molecules as well as intramolecular hydrogen bonds to the internal chloride ligands. The unusually high absorptivity of the MLCT absorption of complex 1 has been explained by TD‐DFT calculations.