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Catalytic Water‐Oxidation Activity of a Weakly Coupled Binuclear Ruthenium Polypyridyl Complex
Author(s) -
Matias Tiago A.,
Mangoni Ana P.,
Toma Sergio H.,
Rein Francisca N.,
Rocha Reginaldo C.,
Toma Henrique E.,
Araki Koiti
Publication year - 2016
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.201600889
Subject(s) - chemistry , ruthenium , catalysis , cerium , medicinal chemistry , redox , electron transfer , inorganic chemistry , photochemistry , stereochemistry , organic chemistry
The catalytic oxidation of water by the binuclear complex [Ru 2 (H 2 O) 2 (bpy) 2 (tpy 2 ph)](PF 6 ) 4 [bpy = 2,2′‐bipyridine; tpy 2 ph = 1,3‐bis(4′‐2,2′:6′,2′′‐terpyridin‐4‐yl)benzene] was investigated comparatively to its mononuclear counterpart [Ru(H 2 O)(bpy)(phtpy)](PF 6 ) 2 (phtpy = 4′‐phenyl‐2,2′:6′,2′′‐terpyridine). These catalysts were prepared from the synthesis of their precursor chloride complexes, which were also extensively characterized in this work. The H 2 O–Ru II complexes were found to undergo proton‐coupled electron‐transfer processes to generate the redox species HO–Ru III , O=Ru IV , and O=Ru V . The catalytically active species, [Ru V 2 (O) 2 (bpy) 2 (tpy 2 ph)] 6+ and [Ru V (O)(bpy)(phtpy)] 3+ , were generated electrochemically and by using cerium(IV) ammonium nitrate. In the presence of Ce IV , the catalytic rates for O 2 production by the binuclear and mononuclear species were 1.9 × 10 –3 and 9.5 × 10 –5 s –1 , respectively. This superior catalytic performance of the binuclear complex suggests that, despite weak electronic coupling between the Ru centers, the second site could play an important mechanistic role in the formation of the activated species [(bpy)(OO)Ru IV (tpy 2 ph)Ru III (OH)(bpy)] 4+ .