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Effect of Pyridyl Substitution on Chemical and Photochemical Water Oxidation by [Ru(terpyridine)(bipyridine)(OH 2 )] 2+ Scaffolds
Author(s) -
Patel Jully,
Majee Karunamay,
Ahmad Ejaz,
Das Babulal,
Padhi Sumanta Kumar
Publication year - 2017
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201601193
Subject(s) - chemistry , pyridine , catalysis , protonation , ruthenium , medicinal chemistry , terpyridine , bipyridine , ring (chemistry) , photochemistry , inorganic chemistry , crystallography , crystal structure , organic chemistry , ion , metal
The complexes [Ru(2‐py‐tpy)(bpy)(OH 2 )][PF 6 ] 2 ( 1 ; bpy = 2,2′‐bipyridine), [Ru(3‐py‐tpy)(bpy)(OH 2 )][PF 6 ] 2 ( 2 ), and [Ru(4‐py‐tpy)(bpy)(OH 2 )][PF 6 ] 2 ( 3 ; n ‐py‐tpy = 4′‐( n ‐pyridyl)‐2,2′:6′,2′′‐terpyridine, n = 2–4), as electronic modifications of the [Ru(tpy)(bpy)(OH 2 )][PF 6 ] 2 scaffold, have been synthesized and characterized thoroughly by several spectroscopic methods. All three complexes were employed as catalysts for chemical and photochemical water oxidation. The free nitrogen atom of the pyridine ring in catalysts 1 – 3 is protonated at pH 1 and acts as an electron‐withdrawing group. For 2 , the meta ‐nitrogen atom has a larger withdrawing effect compared with those of 1 and 3 , as the positive charge (δ+) is delocalized only at the carbon atoms. However, the positive charge (δ+) is distributed among the nitrogen and carbon atoms of the pyridine ring for the ortho ‐ and para ‐nitrogen atoms in 1 and 3 , respectively. Electrochemical and manometry studies revealed that 1 and 3 are better catalysts owing to the weaker electron‐withdrawing effects than that for 2 . All of these complexes also act as efficient catalysts towards the photo‐oxidation of water in pH 6.5 phosphate buffer at 20 °C in the presence of [Ru(bpy) 3 ] 2+ as a photosensitizer and Na 2 S 2 O 8 as a sacrificial electron acceptor.