Mixed-valence, layered, cation radical salts of the ethane-bridged dimeric tetrathiafulvalene [(EDT-TTF-CH₂-)₂#centre dot#⁺] [X^-][THF]_0.5, X^-=FeCl₄^-, GaCl₄^-

The synthesis and X-ray crystal structure of the ethane-linked dimeric tetrathiafulvalene [(EDT-TTF-CH2)(2)], 1,2-bis(ethylenedithiotetrathiafulvalenyl)ethane (1), is reported. It oxidizes reversibly at 0.45 and 0.90 V vs SCE. Electrocrystallization in the presence of [n-Bu4N][FeCl4] or [n-Bu4N][GaCl4] affords isostructural, mixed-valence conducting 1:1 salts [1(.+)][FeCl4-][THF](0.5) and [1(.+)][GaCl4-][THF](0.5) whose X-ray crystal structures are described. The intercalation of the tetrahedral anions within the organic slabs and the resulting sliding of the molecular diads on top of each other give rise to both 1D- and 2D-type HOMO ... HOMO interactions whose origin is correlated with the details of the peculiar overlap patterns obtained with those dimeric tetrathiafulvalenes. The weak paramagnetism observed in the GaCl4- salt due to the organic spins of the conducting slabs is hidden in the FeCl4- salt by the S = 5/2 Fe(III) contribution. The absence of sizable magnetic interactions between the organic and FeCl4- sublattices is accompanied by weak antiferromagnetic FeCl4-/FeCl4- interactions, attributable to a short Cl ... Cl interanion distance at 3.419(17) Angstrom.