New conducting radical salts based upon Keggin-type polyoxometalates and perylene

Three new radical salts, Per6[PMo12O40]·CH2Cl2 (1), Per6[PMo12O40]·CH3CN (2), and Per9(NBu4)4[SiW12O40]2 (3) (Per = perylene), have been synthesised and their electrical and magnetic properties characterised. These three salts are diamagnetic and they behave as semiconductors with room temperature conductivities of 69, 3.6 and 0.85 S cm−1. While salt 2 presents hole-type conduction and 3 exhibits electron-dominated electrical transport properties, salt 1 shows at 150 K an abrupt change in the thermal dependence of the electrical conductivity and the Seebeck coefficient suggesting a phase transition.

Cooperativity in the Iron(II) Spin-Crossover Compound [Fe(ptz)6](PF6)2 under the Influence of External Pressure (ptz = 1-n-Propyltetrazole)

The iron(II) spin-crossover compound [Fe(ptz)(6)](PF(6))(2) (ptz = 1-propyltetrazole) crystallizes in the triclinic space group Ponemacr;, with a = 10.6439(4) Å, b = 10.8685(4) Å, c = 11.7014(4) Å, alpha = 75.644(1) degrees, beta = 71.671(1) degrees, gamma = 60.815(1) degrees, and Z = 1. In [Fe(ptz)(6)](PF(6))(2), the thermal spin transition is extremely steep because of cooperative effects of elastic origin. The transition temperature at ambient pressure is 74(1) K. An external pressure of 1 kbar shifts the transition temperature to 102(1) K, corresponding to a stabilization of the low-spin state, which is smaller in volume. The volume difference between the high-spin and the low-spin stat…

Metallic Conductivity Down to 2 K in a Polyoxometalate-Containing Radical Salt of BEDO-TTF