The new salt κ-ET2[Hg(SCN)2I]: crystal structure and physical properties

The structure, resistivity and ESR of a new organic conductor κ-ET2[Hg(SCN)2I](ET=bis(ethylenedithio) tetrathiafulvalene) are studied. Its main crystallographic parameters are found to be: M-1213.2, a-38.03(1), b= 11.80(1), c = 8.329(9) Å; γ=98.1(2)°; V-3700(2) Å3; space group P21Ib; Z = 4. It is shown that the radical cations are packed according to the κ-type in the organic sheets, and the anions form polymerized chains. Two different radical cation layers with different amounts of shortened S···S contacts and distinct interaction between anionic and cationic sheets are found. ESR linewidth is found to be 9-11G (300 K), which is substantially narrower than a typical linewidth for ET-based radical cation salts of the κ-type. Based on temperature dependences of the resistance anisotropy and ESR parameters, we suggest that a structure rearrangement with electron localization may take place around 50 K. The comparison of crystal structure and properties of the title compound with other salts of the family ET2[Hg(SCN)3−nXn], where X=Cl, Br, and n = 1.2, is camed out.