PERYLENE SALTS WITH TETRAHALOGENOFERRATE(III) ANIONS - SYNTHESIS, CRYSTAL-STRUCTURE OF [(C20H12)(3)][FECL4] AND CHARACTERIZATION

Two new perylene (C20H12) salts [(C20H12)(3)][FeCl4] 1 and [(C20H12)(3)][FeBr4] 2 have been synthesised and characterised. Compound 1 crystallises in the triclinic system, space group P (1) over bar, with a = 12.8393(11), b = 14.1333(11), c = 14.8391(14) Angstrom, alpha = 91.680(7), beta = 113.114(7), gamma = 115.119(7) and Z = 2, and its structure consists of tetramerised stacks of perylenes flanked by additional pseudo-orthogonal perylene molecules and tetrachloroferrate(III) anions. Resistivity and thermopower measurements characterise [(C20H12)(3)][FeCl4] 1 as a semiconductor with a room-temperature conductivity sigma approximate to 0.17 S cm(-1) with an activation energy of 0.12 eV. The magnetic behaviour of both compounds is dominated by the contribution of the paramagnetic iron(III) centres. Magnetic susceptibility data in the temperature range 3-300 K were fitted to the equation for a binuclear S = S' = 5/2 interaction, with J/k = -1.26(1) K and g = 2.022(4) for 1 and J/k = -3.72(4) K and g = 2.03(2) )for 2.