Preparation and spectroscopic properties of bis(2,2′-bipyridine)-ruthenium(II) complexes and related complexes with sulfur-rich dithiolato ligands and electrical conductivities of their oxidized species

Ru(bpy)2L [bpy=2,2′-bipyridine; L=C3S5 2− (4,5-disulfanyl-1,3-dithiole-2-thionate(2−)) or C8H4S8 2− [2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithionate(2−)] and [NBun 4][Ru(C3S5)2] were prepared. The Ru(bpy)2L (L=C3S5 2− and C8H4S8 2−) complexes exhibit Ru(II)/Ru(III) redox potentials of −0.05 and −0.35 V (vs. SCE), respectively, and the dithiolate ligands are further oxidized at +0.62 and +0.26 V (vs. SCE). [NBun 4][Ru(C3S5)2] is oxidized at +0.25 V (vs. SCE) in the C3S5 ligand, the Ru(III) ion being reduced to the Ru(II) ion at −0.32 V. The Ru(bpy)2L complexes were oxidized by iodine to afford essentially one-electron and over two-electron oxidized species as solids, where the metal oxidation occurs in the former species and the dithiolate ligands are further oxidized in the latter species. [NBun 4][Ru(C3S5)2] was oxidized by iodine to give [NBun 4]0.1[Ru(C3S5)2]. The oxidized species [Ru(bpy)2(C8H4S8)](I3)2.1 and [NBun 4]0.1[Ru(C3S5)2] exhibit electrical conductivities of 2.0×10−4 and 1.8×10−3 S cm−1, respectively, measured for compacted pellets at room temperature, while the conductivities of the other oxidized species obtained are small (<10−6 S cm−1). Electronic states of the complexes are discussed on the basis of IR, electronic absorption, and ESR spectra.