An in Situ X-ray Absorption Fine Structure Study of Different Oxidation States of Oxo- and Hydroxo-Bridged Ruthenium Dimers in Acetonitrile Solution

Abstract

X-ray absorption fine structure (XAFS) experiments have been performed in acetonitrile solution with an in situ electrochemical cell at controlled electric potentials on [Ru(2)(&mgr;-O) (&mgr;-CH(3)COO)(2)(bpy)(2)L(2)](n)()(+) (bpy = 2,2'-bipyridine; L = pyridine (1) and 1-methylimidazole (2)) with the formal ruthenium oxidation states Ru(II)Ru(III), Ru(III)Ru(III), and Ru(III)Ru(IV). Spectra were also recorded for the corresponding hydroxo-bridged species, abbreviated as Ru(II)Ru(II)H, Ru(II)Ru(III)H, and Ru(III)Ru(III)H, which were formed by addition of p-toluenesulfonic acid to 1 and 2 and subsequent electrolysis. The X-ray absorption near edge structure (XANES) spectra all showed similar features, although a small shift toward higher threshold energy was observed with increasing formal ruthenium oxidation state. It is concluded from the analysis of the EXAFS data that the ruthenium-ruthenium distance of the &mgr;-oxo complexes decreases with decreasing formal ruthenium oxidation state, interpreted as resulting from decreased electrostatic repulsion between the ruthenium atoms. However, for the &mgr;-hydroxo complexes the ruthenium-ruthenium distance decreases in the order Ru(III)Ru(III)H > Ru(II)Ru(II)H > Ru(II)Ru(III)H. The present coordination structures of the oxo- and hydroxo-bridged ruthenium dimers of the different oxidation states are compared with related iron and vanadium dimers.

An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO3, and Na2CO3 solutions

“…In-situ X-ray spectroelectrochemistry [20][21][22][23][24][25][26][27][28] can be used to determine the formal potentials as well as the relative concentrations of the species at an applied potential, even if sample solutions contain other redox-active species or there is an overlying optical transition that prohibits the direct determination of the concentrations. EXAFS spectra may undergo Fourier transform into frequency space, providing a radial distribution function.…”

Di-μ-acetato-κ4O:O′-μ-oxido-κ2O:O′-bis[cis-(2,2′-bipyridine-κ2N,N′)-trans-(pyridine-κN)ruthenium(III)] bis(hexafluoridophosphate)

“…For related structures, see: Zhang et al (2011); Sudha & Chakravarty (1996). For background to hemerythrin-type diruthenium(III) complexes, see: Abe et al (2002); Dean (1985); Tembe & Ganeshpure (1999); Fukumoto et al (1998); Inomata et al (1999); Sasaki (1995); Sasaki et al (1991); Valli et al (1997). For the synthesis, see: Sasaki et al (1991); Ido et al (2013).…”

Characterization of novel redox-active triruthenium(III) complexes with a disulfide alkyl ligand. Anion-dependent redox behaviour of monolayer assemblies on gold †

“…14 Among the series, protoncoupled electron-transfer reactions were observed for monolayers of the (µ-oxo)dimetal complexes, 11, 12 as found for the discrete analogues dissolved in solution. 15 The present study explores the preparation and electrochemistry of monolayers with (µ 3 -oxo)hexakis(µ-acetato)triruthenium() cores, displaying a well defined reversible redox response in water media. The oxo-centred, acetate-bridged triruthenium complexes of the type [Ru 3 (O)(CH 3 CO 2 ) 6 L 3 ] nϩ (L = a monodentate ligand) 16,17 constitute a well known class of transition-metal cluster compounds owing to their reversible multi-step redox chemistry.…”