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

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 BF4-. In compound 5.(I-3), according to the temperature-controlled EPR and Mossbauer measurements, the VT moiety is oxidised to form a radical, while the two ferrocene groups are not oxidized. In compound 5H.(BF4)(4), however, a mixed ferrocene/ferrocenium system consisting of low-spin Fe(II), high-spin Fe(II) and Fe(III) is detected by Mossbauer spectroscopy. Due to the protonation of VT by HBF4, the extended pi-electron system of VT is degraded into the TTF system. The electrical conductivities of pressed pellets of the radical cationic salts are 7 x 10(-3) S cm(-1).