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.
X-ray absorption spectroscopy combined with an in-situ electrochemical cell has been developed for characterization of unstable, but electrochemically stable metalloprotein model compounds with various oxidation states in solution. The technique has been applied to some dimanganese Sehiff base complexes as a model of Photosystem II and [Ru2(t-O)(}-CH3COO)2(bpy)2L] 2(L=pyridine and l. -methylimidazole) as a model off hemerythrin. It has been found that X-ray absorption near-edge structure (XANES) patterns correlate well with the formal oxidation states of the metal ions and aggregation. The analysis of extended X-ray absorption fine structure (EXAFS) data has revealed characteristic metal-ligand and metal-metal distances within the model compounds with different oxidation states.
A non-linear relationship between the conformational change of an n-propyl moiety and photochromic reaction was observed by performing time-dependent X-ray diffraction experiments.
Crystalline-state photochromism of a new organorhodium dinuclear complex having n-methoxypropyltetramethylcyclopentadienyl (η-C5Me4n-C3H6OCH3) and photoresponsive dithionite (μ-O2SSO2) ligands was investigated directly by performing single crystal X-ray diffraction experiments; reversible conformational change of...
Crystalline-state photoreaction of a newly prepared organorhodium dithionite complex with n-hexyltetramethylcyclopentadienyl (CpHex: η5-C5Me4n-Hexyl) ligands was studied by single crystal X-ray diffraction experiments; 2π/5 rotation of the CpHex ligand is induce...
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