Synthesis and Characterization of Charge Transfer Salts Based on [M(dcdmp)2] (M = Au, Cu and Ni) with TTF Type Donors

The charge transfer salts alpha-DT-TTF[Au(dcdmp)(2)] (1), BET-TTF[Au(dcdmp)(2)] (2M and 2T), alpha-DT-TTF[Cu(dcdmp)(2)] (3), ET[Cu(dcdmp)(2)] (4), (BET-TTF)(2)[Cu(dcdmp)(2)] (5), (ET)(2)[Ni(dcdmp)(2)] (6), and alpha-mtdt[Cu(dcdmp)(2)] (7) were obtained by electrocrystallization of different electron donor molecules derived from TTF (alpha-DT-TTF = alpha-dithiophene-tetrathiafulvalene; BET-TTF = (bis(ethylenethio)tetrathiafulvalene; ET = bis(ethylenedithio)-tetrathiafulvalene; alpha-mtdt = alpha-methylthiophenetetrathiafulvalene) in the presence of transition metal complex [M(dcdmp)(2)] (M = Au (III), Cu (III) and Ni (II)) (dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine). Compounds 1 and 2 (2M and 2T) have a similar packing pattern composed of mixed stacks of alternating donor-acceptor molecules. For (BET-TTF)[Au(dcdmp)(2)] two different crystal structures (2M and 2T) were obtained indicating polymorphism. Compounds 3 and 4 are isostructural being composed of zigzag chains of alternating donor and acceptor molecules. The salts with a 2:1 stoichiometry, (BET-TTF)(2)[Cu(dcdmp)(2)] (5), and (ET)(2)[Ni(dcdmp)(2)] (6) present the donor molecules fully oxidized and [M(dcdmp)(2)] (M = Ni and Cu) in a dianionic state. The salt of the dissymmetric donor alpha-mtdt with [Cu(dcdmp)(2)], alpha-mtdt[Cu(dcdmp)(2)] (7) has a crystal structure composed of segregated donor stacks that are positioned in a head-to-head fashion and alternate with the anion stacks. All charge transfer salts (1-7) are modest semiconductors with conductivities in the range 10(-1)-10(-5) S/cm, with the highest values obtained in alpha-DT-TTF salts, compounds 1 and 3.