1,1'-DISUBSTITUTED FERROCENES AS DONORS FOR CHARGE-TRANSFER COMPLEXES- SYNTHESIS, STRUCTURE, CONDUCTIVITY, AND MAGNETIC-PROPERTIES

Starting from ferrocene-1,1'-dicarbaldehyde (1), the novel electron do nors hiolo[4,5b][1,4]dithiin-2-ylidene)methyl]ferrocene (5), '-bis[(1, 3-benzodithiol-2-ylidene)methyl]ferrocene (6), and bis[2-[4-)methylthi o)phenyl]-(E)-ethenyl]ferrocene (7) were prepared, and their electroch emical properties were studied. 5 and 6 undergo two reversible oxidati on processes, whereas for 7 only the first electron removal is reversi ble in character. Crystals of 5 are monoclinic, space group P2(1)/c, w ith a = 12.448(1) angstrom, b = 12.178(1) angstrom, c = 16.219(1) angs trom, beta = 104.5(1)degrees, and Z = 4. In the solid state, molecules of 5 assume an eclipsed conformation, with the two substituents lying on top of each other (intramolecular stacking). 5 and 6 easily form 1 :2 electron-transfer complexes with TCNQ (8 and 9, respectively), wher eas 7 leads to a charge-transfer (CT) complex (10). Polycrystalline sa mples of 8 and 9 are conducting: sigma(rt)(8) = 0.26 S.cm-1 and sigma( rt)(9) = 0.20 S.cm-1. SQUID magnetic susceptibility measurements of 8 and 9 show these materials to undergo a phase transition dominated by a weak antiferromagnetic coupling (Curie-Weiss constants theta (8) = - 3 K and theta (9) = -3 K). 10 is an insulator and is characterized by a very weak degree of electron transfer. Crystals of 10 are triclinic, space group P1BAR, with a = 7.796(1) angstrom, b = 8.607(1) angstrom, c = 16.396(2) angstrom, alpha = 92.88(1)degrees, beta = 97.83(1)degre es, gamma = 100.95(1)degrees, and Z = 1. In the CT complex 10, the don or 7 assumes an antiperiplanar conformation, thus leading to a 1D-DADA type structure.