Synthesis and Catalytic Water Oxidation Activities of Ruthenium Complexes Containing Neutral Ligands

Abstract

Two dinuclear and one mononuclear ruthenium complexes containing neutral polypyridyl ligands have been synthesised as pre-water oxidation catalysts and characterised by (1)H and (13)C NMR spectroscopy and ESI-MS. Their catalytic water oxidation properties in the presence of [Ce(NH(4))(2)(NO(3))(6)] (Ce(IV)) as oxidant at pH 1.0 have been investigated. At low concentrations of Ce(IV) (5 mM), high turnover numbers of up to 4500 have been achieved. An (18)O-labelling experiment established that both O atoms in the evolved O(2) originate from water. Combined electrochemical study and electrospray ionisation mass spectrometric analysis suggest that ligand exchange between coordinated 4-picoline and free water produces Ru aquo species as the real water oxidation catalysts.

Artificial Photosynthesis: Molecular Systems for Catalytic Water Oxidation

“…Structure of the [Ru 2 (OH) 2 (3,6-tBu 2 qui) 2 (btpyan)] 2+ complex 39 containing the redox-active quinone ligand, the analogous bpy complex [Ru 2 (OH) 2 (bpy) 2 (btpyan)] 2+ 40, the single-site analogue of complex 39, [Ru(OH 2 )(3,6-tBu 2 qui)(tpy)] 2+ (41), and the [Ru 2 (μ-Cl)(bpy) 2 (btpyan)] 3+ complex 42. 189 However, a more effective way of achieving this was accomplished by the group of Åkermark and Sun, who demonstrated that lowering of the oxidation potential of the catalysts could be accomplished by introducing anionic ligands into the ligand frameworks of the WOCs. Generally, the redox potentials of metal complexes can be tuned by ligand modification, and the incorporation of negatively charged ligands into metal complexes has previously been shown to stabilize metal centers at higher oxidation states and result in complexes with significantly lowered redox potentials.…”

Catalytic Water Oxidation by Ruthenium Complexes Containing Negatively Charged Ligand Frameworks

“…Examples of such dinuclear Ru-based WOCs [18][19][20][21][22] are depicted in Figure 2, and include Meyer's "blue dimer" (1), [23,24] the Ru-Hbpp catalyst [Ru 2 (OH 2 ) 2 (bpp)(tpy) 2 ] 21 (2; Hbpp 5 2,2 0 -(1H-pyrazole-3,5-diyl)dipyridine; tpy 5 2,2 0 ;6 0 ,2 00 -terpyridine), [25][26][27] and a family of Ru complexes, such as complex 3, which is based on a 3,6-bis-[6 0 -(1 00 ,8 00 -naphthyrid-2 00 -yl)-pyrid-2 0 -yl]pyridazine ligand. [28][29][30] …”

Mechanism of Water Oxidation by Ferrate(VI) at pH 7–9

“…[35,36] Oxygen evolution by coupling of two metal oxo groups (mechanism B) has also been found in an umbero fs ystems. [11,21,[37][38][39][40] Mechanism C has not been demonstrated,b ut the reverse reactionh as been reported for an umber of Cu I complexes. [41] On the other hand, for mechanismD,w ehave recently shown that in the presence of BF 3 in CH 3 CN, MnO 4 À undergoes intramolecular coupling of two oxo ligands to generateO 2 .…”

“…[1][2][3][4][5] Water oxidation provides an abundant source of protons and electrons for fuel production. An umber of WOCsb ased on ruthenium, [6][7][8][9][10][11][12] cobalt, [13][14][15][16] manganese, [17][18][19] and iridium [20][21][22][23][24][25] complexes have been reported recently.…”