Catalytic Water‐Oxidation Activity of a Weakly Coupled Binuclear Ruthenium Polypyridyl Complex. Issue 36 (22nd November 2016)

• Record Type: Journal Article
• Authors: Matias, Tiago A.; Mangoni, Ana P.; Toma, Sergio H.; Rein, Francisca N.; Rocha, Reginaldo C.; Toma, Henrique E.; Araki, Koiti
• Is Part Of: European journal of inorganic chemistry. Issue 36(2016)
• Page Start: 5547
• Page End: 5556
• Publication Date: 2016-11-22
• Subjects: Electrocatalysis -- Electronic coupling -- Oxygen -- Ruthenium -- Water splitting; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201600889
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : The catalytic oxidation of water by the binuclear complex [Ru2 (H2 O)2 (bpy)2 (tpy2 ph)](PF6 )4 [bpy = 2, 2′‐bipyridine; tpy2 ph = 1, 3‐bis(4′‐2, 2′:6′, 2′′‐terpyridin‐4‐yl)benzene] was investigated comparatively to its mononuclear counterpart [Ru(H2 O)(bpy)(phtpy)](PF6 )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 H2 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 (tpy2 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 O2 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 (tpy2 ph)Ru III (OH)(bpy)] 4+ . Abstract : A weakly coupled binuclear complex shows a rate constant for oxygen evolution that is up to 20 times larger than that of the analogous mononuclear complex, which indicates a major role of the second site on the catalytic activity.