Electrochemical and NMR spectroscopic studies of selenium- and tellurium-substituted ferrocenes II:: Diferrocenyl chalcogenides Fc2E, diferrocenyl dichalcogenides, Fc2E2 and bis(ferrocenylchalcogeno)-alkanes, FcE(CH2)nE′Fc (E, E′ = Se: n=1, 2, 3; E, E′ = Te: n=1, 3; E = Se, E′ = Te: n=3; Fc = [Fe(η5-C5H5)(η5-C5H4)])

1,3-Bis(ferrocenylehalcogeno)propanes, FcE(CH2)(3)E'Fc (E, E' = Se, Te), and 1,2-bis(ferrocenylseleno)ethane, FcSe(CH2)(2)SeFc have been prepared, characterised, and included in a spectroscopic and electrochemical study of a series of compounds containing two ferrocenes linked by a chalcogen-containing bridge. Cyclic and differential pulse voltammetry show that there is electronic communication between the two ferrocene units when the bridge is short (as in Fc(2)E), but that the interaction rapidly becomes weaker with increasing Fe center dot center dot center dot Fe distance, and is undetectable for the ethane and propane derivatives. Se-77 and Te-125 NMR spectroscopic measurements reveal that the Se-77 chemical shift of Fc(2)Se(2) is anomalously high, which correlates with the long wavelength of its lowest energy electronic absorption. (c) 2006 Elsevier B.V. All rights reserved.