Treatment of [RuCl2(DMSO)(4)] with 2-aminoethanethiol (Haet) in ethanol gave a dicationic triruthenium complex, [Ru{Ru(aet)(3)}(2)]Cl-2 ([1]Cl-2). Complex [1]Cl-2 was also obtained by treatment of RuCl(3)center dot nH(2)O with excess Haet in water. When [1](2+) was chromatographed on a cation-exchange column of SP-Sephadex C-25, meso (Delta Lambda) and racemic (Delta Delta/Lambda Lambda) isomers of the corresponding tricationic complex, [Ru{Ru(aet)(3)}(2)](3+) ([2](3+)), were eluted with aqueous NaNO3. The racemic isomer of [2](3+) was optically resolved into Delta Delta and Lambda Lambda isomers by using [Sb-2(R,R-tartrato)(2)](2-) as a resolving agent. The molecular structures of Delta Lambda- and Delta Delta/Lambda Lambda-[2](NO3)(3) were determined by X-ray crystallography. In these complexes, the central Ru atom is coordinated by six thiolato groups from two terminal fac-(S)-[Ru(aet)(3)] units in an octahedral geometry, forming a linear-type S-bridged triruthenium structure. The spectroelectrochemical studies on the electronic absorption and CD spectra, together with the electrochemical studies, demonstrated that [1](2+) and [2](3+) are interconvertible with each other through a one-electron redox process, retaining the chirality of the triruthenium structure. Their electronic structures were investigated on the basis of EPR and magnetic susceptibility measurements, which indicated that [1](2+) and [2](3+) have spin ground states of S-t = 0 and S-t = 1/2, respectively. The corresponding L-cysteinato complex, [Ru{Ru(L-cys-N,S)(3)}(2)](3-), which was formed from RuCl(3)center dot nH(2)O and excess L-cysteine (L-H(2)cys) in water followed by air oxidation, is also presented.