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Effects of a strong π-accepting ancillary ligand on the water oxidation activity of weakly coupled binuclear ruthenium catalysts

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Abstract

Significant differences were found in the proton-coupled redox chemistry and catalytic behavior of the binuclear [{Ru(H2O)(bpz)}2(tpy2ph)](PF6)4 complex [bpz = 2,2′-bipyrazine; tpy2ph = 1,3-bis(4′-2,2′:6′,2′′-terpyridin-4-yl)benzene] as compared with the structurally analogous derivative with 2,2′-bipyridine (bpy) instead of bpz. The differences were assigned to the stronger π-accepting character of bpz relative to bpy as the ancillary ligand. The expectation of a positive shift for the Ru-centered redox potentials was confirmed for the lower oxidation state species, but that trend was reversed in the formation of the high-valence catalytic active species as shown by a negative shift of 0.14 V for the potential of the [RuIV/V[double bond, length as m-dash]O] process. Moreover, DFT calculations indicated a significant decrease of about 15% on the spin density and oxyl character of the [RuV[double bond, length as m-dash]O]3+ fragment. The significantly lower kcat(O2) for the bpz system was attributed to these combined electronic effects.

Graphical abstract: Effects of a strong π-accepting ancillary ligand on the water oxidation activity of weakly coupled binuclear ruthenium catalysts

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Publication details

The article was received on 18 Dec 2018, accepted on 05 Feb 2019 and first published on 05 Feb 2019


Article type: Paper
DOI: 10.1039/C8DT04963G
Citation: Dalton Trans., 2019, Advance Article

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    Effects of a strong π-accepting ancillary ligand on the water oxidation activity of weakly coupled binuclear ruthenium catalysts

    T. A. Matias, F. N. Rein, R. C. Rocha, A. L. B. Formiga, H. E. Toma and K. Araki, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C8DT04963G

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