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Ru(ii) water oxidation catalysts with 2,3-bis(2-pyridyl)pyrazine and tris(pyrazolyl)methane ligands: assembly of photo-active and catalytically active subunits in a dinuclear structure.
- Source :
-
Dalton transactions (Cambridge, England : 2003) [Dalton Trans] 2020 Mar 14; Vol. 49 (10), pp. 3341-3352. Date of Electronic Publication: 2020 Feb 27. - Publication Year :
- 2020
-
Abstract
- Two mononuclear Ru(ii) complexes, i.e. [RuCl(κ <superscript>3</superscript> N-terpy)(κ <superscript>2</superscript> N-dpp)]PF <subscript>6</subscript> ([1]PF <subscript>6</subscript> ; terpy = 2,2':6',2''-terpyridine; dpp = 2,3-bis(2'-pyridyl-pyrazine) and [RuCl(κ <superscript>3</superscript> N-tpm)(κ <superscript>2</superscript> N-dpp)]Cl ([2]Cl; tpm = tris(1-pyrazolyl)methane), and one dinuclear complex, i.e. [Ru <subscript>2</subscript> Cl(κ <superscript>3</superscript> N-tpm)(μ-κ <superscript>2</superscript> N:κ <superscript>2</superscript> N-dpp)Ru(κ <superscript>2</superscript> N-bpy) <subscript>2</subscript> ][PF <subscript>6</subscript> ] <subscript>3</subscript> ([3][PF <subscript>6</subscript> ] <subscript>3</subscript> ; bpy = 2,2'-bipyridine), have been synthesized and their water oxidation catalytic properties have been investigated. A combined DFT and experimental ( <superscript>35</superscript> Cl NMR and conductivity measurements) study aimed to elucidate the nature of [1] <superscript>+</superscript> and [2] <superscript>+</superscript> in aqueous solution has also been performed, indicating that one water molecule is allowed to enter the first coordination sphere of [2] <superscript>+</superscript> in the ground state, replacing one tpm nitrogen. Conversely, in the case of [1] <superscript>+</superscript> , water coordination, assumed to be needed for the water oxidation process, presumably occurs following the oxidation of the metal. For all complexes, a catalytic wave has been detected in acetonitrile/water 1 : 1 (v/v) solution in the range 1.4-1.7 V vs. SCE. In all cases, water oxidation (investigated at pH < 8) takes place initially via a proton-coupled two-electron, two-proton process with the formation of an Ru(iv)[double bond, length as m-dash]O moiety, followed by one electron oxidation and water nucleophilic attack. The TON and TOF values (within the range of 16-33 and 1.3-2.2 h <superscript>-1</superscript> , respectively) of the complexes are higher than those of the benchmark [Ru(LLL)(LL)(OH <subscript>2</subscript> )] <superscript>2+</superscript> -type species (LLL and LL are tridentate and bidentate polypyridine ligands, respectively), which is [Ru(terpy)(bpm)(OH <subscript>2</subscript> )] <superscript>2+</superscript> .
Details
- Language :
- English
- ISSN :
- 1477-9234
- Volume :
- 49
- Issue :
- 10
- Database :
- MEDLINE
- Journal :
- Dalton transactions (Cambridge, England : 2003)
- Publication Type :
- Academic Journal
- Accession number :
- 32103210
- Full Text :
- https://doi.org/10.1039/c9dt04815d