Mixed Radical/Iodine Charge-Transfer Salts of Dithiadiazolyl Diradicals. Structural Characterization of the Pyridine-Bridged 2:1 Salt 2,6-[(S_2N_2C)C_5H_3N(CN_2S_2)]_2[I]

摘要

Cosublimation of 2,5-furanbis(1,2,3,5-dithiadiazolyl) [F-2,5-S] and iodine affords 1:1 and 2:1 charge-transfer salts, [F-2,5-S][I] and [F-2,5-S]_2[I]. Cosublimation of 2,6-pyridinebis-(1,2,3,5-dithiadiazolyl) [P-2,6-S] and iodine affords uniquely the 2:1 charge-transfer salt [P-2,6-S]_2[I]. Crystals of the latter belong to the space group P2_1/c, a = 3.434(3), b = 9.8914(9), c = 30.803(4) A, β = 91.52(3)°, V = 1045.9(9) A~3, Z = 2. The structure consists of [P-2,6-S] molecules stacked along the x direction. Pairs of stacks are linked head-on through iodine atoms, which themselves form disordered stacks running parallel to x. The internal structural parameters of the two CN_2S_2 rings within each molecule suggest that one (linked to iodine) is formally uncharged, while the other is partially oxidized. This latter ring is heavily coordinated through S---N linkages to neighboring CN_2S_2 rings and pyridine. Magnetic susceptibility measurements on [P-2,6-S]_2[I] indicate that it is diamagnetic below 220 K.