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Three distinct functionalisation strategies have been applied to the in, in-[{RuII(trpy)}2(μ-bpp)(H2O)2]3+ (trpy=2,2′:6′,2′′-terpyridine, bpp=bis(pyridine)pyrazolate) water-oxidation catalyst framework to form new derivatives that can adsorb onto titania substrates. Modifications included the addition of sulfonate, carboxylate, and phosphonate anchoring groups to the terpyridine and bis(pyridyl)pyrazolate ligands. The complexes were characterised in solution by using 1D NMR, 2D NMR, and UV/Vis spectroscopic analysis and electrochemical techniques. The complexes were then anchored on TiO2-coated fluorinated tin oxide (FTO) films, and the reactivity of these new materials as water-oxidation catalysts was tested electrochemically through controlled-potential electrolysis (CPE) with oxygen evolution detected by headspace analysis with a Clark electrode. The results obtained highlight the importance of the catalyst orientation with respect to the titania surface in regard to its capacity to catalytically oxidize water to dioxygen. [ABSTRACT FROM AUTHOR]

The structures, spectroscopic properties, electrochemistry, and reactivity of two new isomeric [Ru(Cl)2(L)(DMSO)2] complexes are reported [L is the nonsymmetric chelating ligand 5-phenyl-3-(2-pyridyl)-1 H-pyrazole (H3p), DMSO = dimethyl sulfoxide]. It is shown that there is S-to-O linkage isomerization of the ruthenium(II) sulfoxide complexes upon one electron oxidation. The thermodynamic and kinetic properties of this linkage isomerization differ for each isomeric complex and depend strongly on the protonation grade of the ligand backbone. The corresponding data for these processes were evaluated from electrochemical data. A photolytic reaction of either of these isomers in chloroform is presented and leads to the substitution of one DMSO ligand and the formation of a third complex, [Ru(Cl)3(L)(DMSO)]. The remaining coordinated DMSO ligand retains its binding mode through the sulfur atom to a ruthenium(III) metal center. [ABSTRACT FROM AUTHOR]

A series of RuN6 dinuclear Ru-Hbpp complexes (Hbpp is the dinucleating tetraaza ligand 3,5-bis(pyridyl)pyrazole) of general formula {[RuII(R2-trpy)(MeCN)]2(μ-R1-bpp)}3+, 103+-143+, (R1 = H, Me, or NO2. and R2 = H, Me, MeO; see Scheme 1) has been prepared from their Cl- or AcO- bridged precursors. The complexes have been characterized by UV-vis, NMR, CV, and some by X-ray. Complexes 103+-143+, Ru2II,II, were oxidized by 1 equiv in solution, leading to the mixed valence Ru2II,III complexes 104+-144+ containing one unpaired electron and were characterized by EPR and UV-vis-near-IR, which showed metal-centered spin and the presence of low-energy IVCT bands. The Hab parameter indicates a relatively strong electronic coupling between the two ruthenium centers (class II). Further two electron oxidation in solution of the 103+-143+ led to the formation of EPR silent Ru2III,III complexes 105+-145+, that were further characterized by UV-vis-NIR. TD-DFT calculations are employed to assign the nature of the UV-vis transitions for the complexes in the various oxidation states, which are of metal to ligand charge transfer (MLCT) type for Ru2II,II and ligand to metal charge transfer (LMCT) type for Ru2III,II and Ru2III,III. [ABSTRACT FROM AUTHOR]

The synthesis and the full characterization of a new ruthenium(ii) complex with the pentadentate bispidine ligand L1is reported and shown to be a very active catalyst for olefin epoxidation. The selectivity in the epoxidation of cis- and trans-β-methylstyrene with the formation of cisand transproducts, each, was determined and compared with that of the iron bispidine complex of L1. There is a significant difference in selectivity between the two catalysts in the epoxidation of cis-β-methylstyrene but the epoxidation of trans-β-methylstyrene is highly stereoselective with both catalysts. Based on these results, electrochemical and labeling studies, a radical pathway for the epoxidation and isomerization is proposed, and this is supported by computational data. DFT indicates that, with both catalysts, the epoxidation is based on a stepwise mechanism, which, in the first step leads to a radical-based intermediate. This exists in two configurations, which interconvert with a relatively low energy barrier. The product ratio depends on the relative energies of the two configurations of the radical intermediate and the height of the energy barriers to the cis- and trans-epoxide products. For the Fe-based system there is, as expected, the additional complication of the availability of various spin levels, and multi-state reactivity is observed. The computed structures and energies are in agreement with the observed data. [ABSTRACT FROM AUTHOR]

Three distinct functionalisation strategies have been applied to the in,in-[{Ru(II)(trpy)}2(μ-bpp)(H2O)2](3+) (trpy=2,2':6',2''-terpyridine, bpp=bis(pyridine)pyrazolate) water-oxidation catalyst framework to form new derivatives that can adsorb onto titania substrates. Modifications included the addition of sulfonate, carboxylate, and phosphonate anchoring groups to the terpyridine and bis(pyridyl)pyrazolate ligands. The complexes were characterised in solution by using 1D NMR, 2D NMR, and UV/Vis spectroscopic analysis and electrochemical techniques. The complexes were then anchored on TiO2-coated fluorinated tin oxide (FTO) films, and the reactivity of these new materials as water-oxidation catalysts was tested electrochemically through controlled-potential electrolysis (CPE) with oxygen evolution detected by headspace analysis with a Clark electrode. The results obtained highlight the importance of the catalyst orientation with respect to the titania surface in regard to its capacity to catalytically oxidize water to dioxygen., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of RuN(6) dinuclear Ru-Hbpp complexes (Hbpp is the dinucleating tetraaza ligand 3,5-bis(pyridyl)pyrazole) of general formula {[Ru(II)(R(2)-trpy)(MeCN)](2)(μ-R(1)-bpp)}(3+), 10(3+)-14(3+), (R(1) = H, Me, or NO(2). and R(2) = H, Me, MeO; see Scheme 1) has been prepared from their Cl(-) or AcO(-) bridged precursors. The complexes have been characterized by UV-vis, NMR, CV, and some by X-ray. Complexes 10(3+)-14(3+), Ru(2)(II,II), were oxidized by 1 equiv in solution, leading to the mixed valence Ru(2)(II,III) complexes 10(4+)-14(4+) containing one unpaired electron and were characterized by EPR and UV-vis-near-IR, which showed metal-centered spin and the presence of low-energy IVCT bands. The H(ab) parameter indicates a relatively strong electronic coupling between the two ruthenium centers (class II). Further two electron oxidation in solution of the 10(3+)-14(3+) led to the formation of EPR silent Ru(2)(III,III) complexes 10(5+)-14(5+), that were further characterized by UV-vis-NIR. TD-DFT calculations are employed to assign the nature of the UV-vis transitions for the complexes in the various oxidation states, which are of metal to ligand charge transfer (MLCT) type for Ru(2)(II,II) and ligand to metal charge transfer (LMCT) type for Ru(2)(III,II) and Ru(2)(III,III).