Synthesis strategies and chemistry of nonsymmetrically substituted tetrachalcogenafulvalenes

The discovery of the first organic metal, TTF-TCNQ in 1973 sparked interest in the chemistry of TTF. This interest increased considerably further with the discovery of superconducting salts based on TTF derivatives. Three strategies are known for preparing these disymmetric derivatives. Strategy I is based on the double condensation of dichalcogenolate entities with tetrachloroethylene. Strategy II corresponds to the monocondensation of two 1,3-dichalcogenole rings. Strategy III consists of the replacement of one (or several) hydrogen atom(s) in TTF or TSF (tetraselenafulvalene), specifically, by a substituent (R=alkyl chalcogenoalkyl functional group). Among the three strategies, the last one is currently under full development and is very largely used.