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Rationalizing Photo‐Triggered Hydrogen Evolution Using Polypyridine Cobalt Complexes: Substituent Effects on Hexadentate Chelating Ligands
Author(s) -
Lucarini Fiorella,
Bongni David,
Schiel Philippe,
Bevini Gabriele,
Benazzi Elisabetta,
Solari Euro,
FadaeiTirani Farzaneh,
Scopelliti Rosario,
Marazzi Marco,
Natali Mirco,
Pastore Mariachiara,
Ruggi Albert
Publication year - 2021
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.202100161
Subject(s) - substituent , chemistry , moiety , intramolecular force , ligand (biochemistry) , cobalt , polar effect , chelation , pyridine , medicinal chemistry , stereochemistry , catalysis , photochemistry , organic chemistry , receptor , biochemistry
Four novel polypyridine cobalt(II) complexes were developed based on a hexadentate ligand scaffold bearing either electron‐withdrawing (−CF 3 ) or electron‐donating (−OCH 3 ) groups in different positions of the ligand. Experiments and theoretical calculations were combined to perform a systematic investigation of the effect of the ligand modification on the hydrogen evolution reaction. The results indicated that the position, rather than the type of substituent, was the dominating factor in promoting catalysis. The best performances were observed upon introduction of substituents on the pyridine moiety of the hexadentate ligand, which promoted the formation of the Co(II)H intermediate via intramolecular proton transfer reactions with low activation energy. Quantum yields of 11.3 and 10.1 %, maximum turnover frequencies of 86.1 and 76.6 min −1 , and maximum turnover numbers of 5520 and 4043 were obtained, respectively, with a −OCH 3 and a −CF 3 substituent.