Journal of the American Chemical Society, Vol.117, No.26, 6880-6888, 1995
Charge-Transfer Salts of Benzene-Bridged 1,2,3,5-Dithiadiazolyl Diradicals - Preparation, Structures, and Transport-Properties of 1,3-((S2N2C)C6H4(Cn2S2))(X) and 1,4-((S2N2C)C6H4(Cn2S2))(X) (X=i,Br)
Cosublimation of 1,3- and 1,4-benzene-bis(1,2,3,5-dithiadiazolyl) and iodine/bromine affords crystals of the mixed valence salts 1,3- and 1,4-[(S2N2C)C6H4(CN2S2)][X] (X = I, Br). The crystal structures of the two iodide salts consist of perfectly superimposed stacks of molecular units with interannular spacing along the stacks of 3.487(3) and 3.415(2) Angstrom for the 1,3- and 1,4-derivatives. In both compounds the iodines are disordered along the stacking direction. The 1,3-derivative has a highly one-dimensional structure; there are no short intercolumnar S-S interactions. In the 1,4-derivative, however, lateral S-S contacts of 3.911 Angstrom afford some measure of three-dimensionality. The bromide salt of the 1,4-derivative consists of ribbons of alternating 1,4-[(S2N2C)C6H4(CN2S2)](+) units and bromide ions. Within each molecule one heterocyclic ring is closed shell, i.e., a [CN2S2](+) cation, while the other is a discrete radical. The ribbons are layered in zigzag fashion that maximizes ion pairing and isolates the radical centers. The bromide salt of the 1,3-derivative also forms ribbon-like arrays, but the unit cell repeat consists of four layers of ribbons. Within these layers the [CN2S2] rings are approximately stacked.
Keywords:E = S;ELECTRONIC-PROPERTIES;MAGNETIC-PROPERTIES;DISELENADIAZOLYL RADICALS;ORGANIC METALS;CONDUCTIVITY;DESIGN;TCNQ