Charge-transfer salts based on BET-TTF and the linear ions AuX2− (X = Br, I)

The organic π-electron donor E-bis(ethylenethio)-tetrathiafulvalene (BET-TTF) forms several charge-transfer salts with linear AuX2− (X = Br, I) counterions. Experimental conditions significantly affect the shape and the composition of the charge-transfer crystals. In fact, salts with different stoichiometries are obtained from each counterion. The magnetic behavior of the obtained salts have been studied by EPR spectroscopy. The EPR parameters (g, and ΔHpp) of different mixed valence salts with the same counterion are very similar. The crystal structure of (BET-TTF)AuBr2 has been determined by X-Ray diffraction: triclinic system, P-1, Z=1, a = 5.790(4)Å, b = 7.786(3)Å, c = 9.716(8)Å, α = 75.11(5)°, β = 89.30(4)°, γ = 77.20(5)°, V = 395.5(5)Å3. Single crystal electrical conductivity measurements of (BET-TTF)2AuBr2 show that this salt exhibits a semiconducting behavior with a σ(300) = 1.1 Scm−1 and an energy gap of 0.14 eV.