Abstract

The combination of the electron donor tetrathiafulvalene, ttf, with the gold complex bis(pyrazine-2,3-diselenolate)aurate(III), Au(pds)₂⁻, afforded three different compounds depending on the preparative conditions: (ttf)₂[Au(pds)₂]₂ (1), (ttf)₃[Au(pds)₂]₂ (2) and (ttf)₃[Au(pds)₂]₃ (3). Compound 1 was obtained by interdiffusion of (ttf)₃(BF₄)₂ and (NBuⁿ₄)Au(pds)₂ in acetonitrile. Compounds 2 and 3 were obtained by electrocrystallisation from ttf and (NBuⁿ₄)Au(pds)₂ solutions in dichloromethane and acetonitrile respectively. These compounds were characterised by X-ray diffraction and electrical and magnetic studies. In the crystal structure of compound 1 are two types of ttf motifs; dimers and isolated units. In the structures of compounds 2 and 3 the ttf units are arranged in trimers. In compound 2 the ttf units form trimerised segregated stacks separated by Au(pds)₂ units with their long axis almost parallel to the stacking axis. In 3 each ttf trimer is surrounded by a cage of four Au(pds)₂ units, and is arranged perpendicularly to the nearest neighbouring trimers. Compounds 1 and 2 exhibit a semiconducting behaviour with room temperature conductivities of 10⁻⁴ S cm⁻¹ and 10⁻² S cm⁻¹, respectively. Compound 2 is essentially diamagnetic, while compound 1 shows a large paramagnetic susceptibility, at room temperature χ_p = 13 × 10⁻⁴ emu mol⁻¹, following a Curie–Weiss law above 50 K. Compound 3 is paramagnetic with a temperature independent EPR signal in the range 100–300 K.