Charge transfer salts of benzene-bridged 1,2,3,5-dithiadiazolyl diradicals. Preparation, structures, and transport properties of 1,3- and 1,4-[(S{sub 2}N{sub 2}C)C{sub 6}H{sub 4}(CN{sub 2}S{sub 2})] [X] (X = I, Br)
- Univ. of Arkansas, Fayetteville, AR (United States)
- AT&T Bell Lab., Murray Hill, NJ (United States)
- Univ. of Guelph (Canada)
Cosublimation of 1,3- and 1,4-benzene-bis(l,2,3,5-dithiadiazolyl) and iodine/bromine affords crystals of the mixed valence salts 1,3- and 1,4-[(S{sub 2}N{sub 2}C)C{sub 6}H{sub 4}(CN{sub 2}S2)][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) A 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 A afford some measure of three-dimensionality. The bromide salt of the 1,4-derivative consists of ribbons of alternating 1,4-[(S{sub 2}N{sub 2}C)C{sub 6}H{sub 4}(CN{sub 2}S{sub 2})]{sup +} units and bromide ions. Magnetic susceptibility and conductivity measurements on the two iodide salts indicate weakly metallic behavior at room temperature, with a charge density wave (CDW) driven metal-insulator phase transition occurring near 270 and 190 K for the 1,3- and 1,4-derivatives, respectively. For the 1,4-derivative, analysis of the CDW wavevector associated with the transition affords a degree of charge transfer of 1/4 of electron per radical. 34 refs., 14 figs., 3 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 81698
- Journal Information:
- Journal of the American Chemical Society, Vol. 117, Issue 26; Other Information: PBD: 5 Jul 1995
- Country of Publication:
- United States
- Language:
- English
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