Synthesis and Properties of the Geometrically Controlled Mixed-Valence Tetrahedral RuII2RuIII2L6 Cluster

The reaction of Ru(DMSO)4Cl2 and N,N'-bis[1-(pyridin-2-yl)ethylidene]benzidine (L) in the presence of NaClO4 afforded the tetranuclear ruthenium compound, Ru4L6·10ClO4, by self-assembly. Magnetic and electrochemical measurements clearly indicated the presence of both RuII and RuIII moieties within the tetrahedral ruthenium cluster. The Robin-Day Class II mixed-valence behavior was supported by the UV/Vis-NIR spectra with the electronic coupling parameter Vab of 200 cm–1. It is demonstrated that the mixed-valenceRuII2RuIII2L6 cation was stabilized by controlling the coordination geometries of the ruthenium ions between octahedral and trigonal prismatic to fit the supramolecular structure of the tetranuclear cluster. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)