Molecular wires built from binuclear cyclometalated complexes

被引:128
作者
Fraysse, S [1 ]
Coudret, C [1 ]
Launay, JP [1 ]
机构
[1] CNRS, CEMES, F-31055 Toulouse 4, France
关键词
D O I
10.1021/ja0299506
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Binuclear complexes with cyclometalated ends of the [Ru(bpy)(2)(ppH)](+) type (bpy = 2,2'-bipyridine, ppH = 2-phenylpyridine), linked by various spacers, have been prepared. These spacers are made of one or two triple bonds, or bis-ethynyl aryl groups, with aryl = benzene, thiophene, or anthracene. The complexes with bis-ethynyl aryl spacers are obtained by Sonogashira couplings with suitable bis-alkynes, starting from the [Ru(bpy)(2)(ppBr)](+) synthon. Complexes with one or two triple bonds are obtained from the true alkyne [Ru(bpy)(2)(pp-CCH)](+) cyclometalated precursor, using respectively a Sonogashira coupling with the iodo derivative [Ru(bpy)(2)(PPI)](+), or an oxidative homocoupling. Some complexes with tett-butyl-substituted bipyridine ancillary ligands have also been obtained. Oxidation of the binuclear complexes occurs near 0.5 V, i.e., more easily than with [Ru(bpy)(3)](2+)-based complexes. A single anodic wave is observed, with almost no detectable splitting, corresponding to two closely spaced one-electron processes. Differential pulse voltammetry allows the determination of the corresponding comproportionation constants involving the mixed valence Ru-II-Ru-II forms. Controlled potential electrolysis yields the mixed valence forms in comproportionation equilibrium with homovalent forms. Analysis of the intervalence transitions allows the calculation of the electronic coupling element V-ab. This series of complexes exhibit relatively large couplings when comparing with complexes of similar metal-metal distances, with a special mention for the anthracene-containing spacer, which appears particularly efficient for mediating the metal-metal interaction. The results can be rationalized by theoretical calculations at the extended Huckel level.
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页码:5880 / 5888
页数:9
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