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Spectroscopic Characterisation of a Bio‐Inspired Ni‐Based Proton Reduction Catalyst Bearing a Pentadentate N 2 S 3 Ligand with Improved Photocatalytic Activity
Author(s) -
Gotico Philipp,
Moonshiram Dooshaye,
Liu Cunming,
Zhang Xiaoyi,
Guillot Régis,
Quaranta Annamaria,
Halime Zakaria,
Leibl Winfried,
Aukauloo Ally
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201904934
Subject(s) - catalysis , chemistry , ascorbic acid , photocatalysis , ligand (biochemistry) , photochemistry , trigonal bipyramidal molecular geometry , ultrafast laser spectroscopy , inorganic chemistry , crystallography , spectroscopy , organic chemistry , crystal structure , biochemistry , food science , receptor , physics , quantum mechanics
Inspired by the sulfur‐rich environment found in active hydrogenase enzymes, a Ni‐based proton reduction catalyst with pentadentate N 2 S 3 ligand was synthesised. When coupled with [Ru(bpy) 3 ] 2+ (bpy=2,2′‐bipyridine) as photosensitiser and ascorbate as electron donor in a 1:1 mixture of dimethylacetamide and aqueous ascorbic acid/ascorbate buffer, the catalyst showed improved photocatalytic activity compared with a homologous counterpart bearing a tetradentate N 2 S 2 ligand. The mechanistic pathway of photoinduced hydrogen evolution was comprehensively analysed through optical transient absorption and time‐resolved X‐ray absorption spectroscopy, which revealed important electronic and structural changes in the catalytic system during photoirradiation. The Ni II catalyst undergoes a photoinduced metal‐centred reduction to form a Ni I intermediate with distorted square‐bipyramidal geometry. Further kinetic analyses revealed differences in charge‐separation dynamics between the pentadentate and tetradentate forms.