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

Author(s)

Matias, Tiago A. ^[1] ; Rein, Francisca N. ^[2] ; Rocha, Reginaldo C. ^[2] ; Barboza Formiga, Andre Luiz ^[3] ; Toma, Henrique E. ^[1] ; Araki, Koiti ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Chem, Dept Chem, Av Lineu Prestes 748, BR-05508000 Sao Paulo, SP - Brazil

^[2] Los Alamos Natl Lab, Los Alamos, NM 87545 - USA

^[3] Univ Estadual Campinas, UNICAMP, Inst Chem, POB 6154, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: DALTON TRANSACTIONS; v. 48, n. 9, p. 3009-3017, MAR 7 2019.
• Web of Science Citations: 0

Abstract

Significant differences were found in the proton-coupled redox chemistry and catalytic behavior of the binuclear {[}[Ru(H2O)(bpz)](2)(tpy(2)ph)](PF6)(4) complex {[}bpz = 2,2-bipyrazine; tpy(2)ph = 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 -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 {[}Ru-IV/V?O] process. Moreover, DFT calculations indicated a significant decrease of about 15% on the spin density and oxyl character of the {[}Ru-V?O](3+) fragment. The significantly lower k(cat)(O-2) for the bpz system was attributed to these combined electronic effects. (AU)

• FAPESP's process: 14/50906-9 - INCT 2014: in Functional Complex Materials
• Grantee: Fernando Galembeck
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 18/03576-4 - Mechanistic studies in water oxidation catalysis promoted by ruthenium complexes bearing imidazole units
• Grantee: André Luiz Barboza Formiga
• Support Opportunities: Scholarships abroad - Research