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Abstract: The new compound, (bedt-ttf)[Au(cdc)2], where bedt-ttf stands for bis(3,4;3′,4′-ethylenedithio)2,2′,5,5′-tetrathiafulvalene(+) and cdc for cyanoimidodithiocarbonate(2−), was synthesised. Its structure is monoclinic, space group P21/n, with cell parameters a =6.9031(8)Å, b =21.3213(16)Å, c =7.9833(9)Å, β =91.643(6)°, V =1174.5(2)Å3 and Z =2 and consists of alternated stacking of donor and acceptor moieties along c. This compound is a semiconductor with a room temperature resistivity of 6.5×103 Ωcm and an energy gap 2Δ =0.51eV. The anisotropy and thermal dependence of the ESR signal, only due to the bedt-ttf cations, was studied in the range 4–300K. The static and EPR spin susceptibilities indicate an almost temperature independent value of 2.5×10−4 emu/mol ascribed to a three-dimensional network of antiferromagnetic interactions. [Copyright &y& Elsevier]

The charge transfer salt (DT-TTF)4[Au(pds)2]3 (DT-TTF, Δ2,2′-bithieno[3,4-d]-1,3-dithiol; pds, pyrazine-2,3-diselenate) was prepared and characterised by X-ray diffraction, electrical conductivity, thermoelectric power, magnetic susceptibility and EPR measurements. This compound crystallises in the triclinic system, space group P1¯, with the unit cell parameters a=9.712(5) A˚, b=13.620(5) A˚, c=17.169(5) A˚, α=97.254(5)°, β=106.132(5)°, γ=95.956(5)°, V=2141.10(15) A˚3, Z=1. Its crystal structure consists of a bidimensional network of DT-TTF tetramers and orthogonal anions. The electrical properties indicate it is a small gap semiconductor (2Δ=190 meV), with a room temperature conductivity of σRT=2 S cm−1. The electrical and magnetic properties reveal two types of transitions occurring upon cooling. The first, at 238 K, as a second order change to a large gap semiconducting state and, a lower transition, of first order type, with a large hysteresis between 210 and 150 K, probably associated with a larger structural change in the DT-TTF network. [Copyright &y& Elsevier]

The synthesis and characterisation of two new radical ion salts based on the donor dithiophenetetrathiafulvalene (DT-TTF) and the anion Au(cdc)2 − (cdc=cynanodithioimido carbonate) are described. These salts were characterised as the mixed valence compound (DT-TTF)2(Au(cdc)2) (1) and the completely ionic salt (DT-TTF)(Au(cdc)2) (2). The X-ray crystal structure of both compounds show that they are formed by chains of donor molecules separated by anions, but, whereas in compound 2 the donors form uniform stacks, in compound 1 they are dimerised. The electrical conductivity measured in a single crystal at room temperature is 0.2 S cm−1 for 1 and 1.7×10−2 S cm−1 for 2, both revealing semiconducting behaviour. Magnetic measurements indicate strong antiferromagnetic interactions between the donors in compound 2, and a possible spin-Peierls transition at low temperature for compound 1. [Copyright &y& Elsevier]