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DOI: 10.1039/A905723D (Paper) Reference Section for: J. Mater. Chem., 1999, 9, 2731-2736

Synthesis, crystal structure and properties of the semiconducting molecular charge-transfer salt (bedt-ttf)2Ge(C2O4)3·PhCN [bedt-ttf=bis(ethylenedithio)tetrathiafulvalene]

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Lee Martin, Scott S. Turner, Peter Day, Philippe Guionneau, Judith A. K. Howard, Mikio Uruichi and Kyuya Yakushi

Abstract

The synthesis, crystal structure and physical properties of a new bedt-ttf charge transfer salt containing the tris(oxalato)germanium(IV) anion are described and interpreted. Electrochemical oxidation of neutral bedt-ttf in the presence of (NH4)2Ge(C2O4)3·2H2O in PhCN solution yields crystals of (bedt-ttf)2Ge(C2O4)3·PhCN. The crystal structure has been solved at 296(2) and at 120(2) K. In contrast to the well known tris(oxalato)-metallate(III) salts of bedt-ttf, the structure does not contain alternating layers of bedt-ttf cations and tris(oxalato)metallate anions, but consists of a ‘checker board’ arrangement of face-to-face bedt-ttf dimers with [Ge(C2O4)3]2– interspersed by layers of solvent molecules. Each bedt-ttf molecule has a charge close to +1, which is estimated from the empirical relationship between C[double bond, length as m-dash]C and C–S bond lengths and these charges are correlated with Raman spectra. As expected from the presence of strongly dimerised (bedt-ttf+)2 units the salt is a semiconductor between 300 and 120 K with a low activation energy of 0.127 eV.

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