New radical salts of diferrocenyl-VT (VT: bis(vinylenedithio)tetrathiafulvalene)

Abstract

1,1′-Diferrocenyl-VT 5 is successfully prepared by phosphite-based coupling reaction of ferrocenyl 1,3-dithiol-2-one 4. It shows one reversible cyclic voltammogram with E _pa = 0.66 V and forms radical cation salts with I ₃ ^– and BF ₄ ^– . In compound 5·(I ₃ ), according to the temperature-controlled EPR and Mössbauer measurements, the VT moiety is oxidised to form a radical, while the two ferrocene groups are not oxidized. In compound 5H·(BF ₄ ) ₄ , however, a mixed ferrocene/ferrocenium system consisting of low-spin Fe(II), high-spin Fe(II) and Fe(III) is detected by Mössbauer spectroscopy. Due to the protonation of VT by HBF ₄ , the extended π-electron system of VT is degraded into the TTF system. The electrical conductivities of pressed pellets of the radical cationic salts are 7 × 10 ^–3  S cm ^–1 .