Issue 16, 1998

Synthesis of π-conjugated cobaltadithiolene cyclotrimers and significant effects of electrolyte cation and solvent on their electrochemical, optical and magnetic properties

Abstract

A new class of cobalt cyclic trinuclear complexes with four fused aromatic rings, [Co3(η-C5H5)3(S6C6)] and [Co3(η-C5H4Me)3(S6C6)], was synthesized by a condensation reaction of [Co(η-C5H5)(S2C2H2)] and [Co(η-C5H4Me)(S2C2H2)], respectively, in aqueous halogenoacid solution. The complexes undergo reversible three-step 1e reductions in aprotic media forming two mixed-valence states, with overall charges 1– and 2–. The thermodynamic stability of the mixed-valence complexes estimated from the redox potential differences and the degree of internuclear electronic interaction evaluated from the intervalence-transfer bands depends markedly on the size of the electrolyte cation and the solvent polarity; larger cations and more polar solvents increase the stability and the electronic interaction. The EPR spectra of [Co3(η-C5H5)3(S6C6)] reduced by [Co(η-C5Me5)2] in propylene carbonate (pc) indicate that the 1– and 3– species are paramagnetic with S = ½, whereas the 3– species formed by reduction with Na in thf gives a spectrum of the quartet state (S = [fraction three-over-two]) denoting ferromagnetic interaction. This difference is attributed to a weaker internuclear interaction caused by a stronger electrostatic effect of the smaller counter ion, Na+ in thf, compared to [Co(η-C5Me5)2]+ in pc.

Supplementary files

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1998, 2651-2656

Synthesis of π-conjugated cobaltadithiolene cyclotrimers and significant effects of electrolyte cation and solvent on their electrochemical, optical and magnetic properties

H. Nishihara, M. Okuno, N. Akimoto, N. Kogawa and K. Aramaki, J. Chem. Soc., Dalton Trans., 1998, 2651 DOI: 10.1039/A803028F

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