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Iron Pentapyridyl Complexes as Molecular Water Oxidation Catalysts: Strong Influence of a Chloride Ligand and pH in Altering the Mechanism
Author(s) -
Das Biswanath,
Orthaber Andreas,
Ott Sascha,
Thapper Anders
Publication year - 2016
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.201600052
Subject(s) - chemistry , catalysis , ligand (biochemistry) , chloride , pyridine , rhodium , turnover number , methanol , inorganic chemistry , oxygen , noble metal , transition metal , artificial photosynthesis , metal , ton , medicinal chemistry , organic chemistry , photocatalysis , receptor , biochemistry , fishery , biology
The development of molecular water oxidation catalysts based on earth‐abundant, non‐noble metals is essential for artificial photosynthesis research. Iron, which is the most abundant transition metal in the earth's crust, is a prospective candidate for this purpose. Herein, we report two iron complexes based on the polypyridyl ligand Py5OH (Py5OH=pyridine‐2,6‐diylbis [di(pyridin‐2‐yl)methanol]) that can catalyse water oxidation to produce O 2 in Ru III ‐induced (at pH 8, highest turnover number (TON)=26.5; turnover frequency (TOF)=2.2 s −1 ), Ce IV ‐induced (at pH≈1.5 highest TON=16; TOF=0.75 s −1 ) and photo‐induced (at pH 8, highest TON=43.5; TOF=0.6 s −1 ) reactions. A chloride ligand in one of the iron complexes is shown to affect the activity strongly, improve stability and, thereby, the performance at pH 8 but it inhibits oxygen evolution at pH≈1.5. The observations are consistent with a change in mechanism for catalytic water oxidation with the Fe(Py5OH) complexes between acidic (Ce IV ) and near‐neutral pH (Ru III ).