(PERYLENE)CO(MNT)2(CH2CL2)0.5 - A MIXED MOLECULAR AND POLYMERIC CONDUCTOR

Single crystals of the quasi-one-dimensional conductor (perylene)Co-bis(maleonitriledithiolate)(CH2Cl2)0.5 were prepared by electrocrystallization. The structure at room temperature is incommensurate with modulation wave vector (0.22a*, -0.13b*, -0.36c*). At T = 295 K it crystallizes in space group P1BAR with Z = 2 and lattice parameters a = 6.551 (2) angstrom, b = 11.732 (2) angstrom, c = 16.481 (2) angstrom, alpha = 92.08 (1)-degrees, beta = 95.30 (1)-degrees, gamma = 94.62 (1)-degrees, and V = 1251.1 (5) angstrom 3. The structure consists of almost regular perylene stacks and polymeric chains of dimerized Co-bis(dithiolate) units along the a axis, with the solvent molecules disordered in the free spaces. At room temperature, electrical conductivity (sigma(RT) congruent-to 60 OMEGA-1 cm-1) and absolute thermoelectric power (S(RT) = -8-mu-V K-1) approach metallic behavior at high temperatures. These transport properties and magnetic susceptibility measurements show a metal to insulator transition at 272-277 K and a second semiconductor to semiconductor phase transition at ca. 170-190 K, both with a remarkable hysteresis.