Synthesis, structures and properties of cyclopenteno annelated bis-fused TTF donors and their molecular complexes

A series of cyclopenteno annelated bis-fused TTF derivatives (CP-TTP 1a-d) have been synthesized. The present donors have produced many molecular complexes showing high conductivity. In particular, several cation radical salts based on the bis(methylthio)-(CPTM-TTP 1c) and ethylenedithio (CPET-TTP, 1d) derivatives are metallic down to liquid helium temperature, though resistivity of CPTM-TTP salts increases a little at low temperature. Among metallic salts, (CPTM-TTP)(4)X (X = PF6-, AsF6- and SbF6-) are isostructural and have two-dimensional ''beta-type'' arrangement of donor molecules. The band calculations of these salts indicate they have eclipsed Fermi surfaces characteristic of two-dimensional metals.