Trans-4,4{prime}-dichloro-1,1{prime},2,2{prime},3,3{prime}-tetrathiadiazafulvalene (DC-TAF) and its 1:1 radical cation salts [DC-TAF][X]: Preparation and solid-state properties of BF{sub 4{minus}}, ClO{sub 4{minus}}, and FSO{sub 3{minus}} derivatives
Reductive coupling of 4,5-dichloro-1,2,3-dithiazolylium chloride yields trans-4,4{prime}-dichloro-1,1{prime},2,2{prime},3,3{prime}-tetrathiadiazafulvalene (DC-TAF), the first example of this heterofulvalene system. Ab initio molecular orbital (B3LYP/6-31G**) calculations on prototypal TAF confirm that the closed shell {sup 1}A{sub g} state lies 22 kcal mol{sup {minus}1} below the {sup 3}B{sub u} diradical triplet. Cyclic voltammetry on DC-TAF reveals two reversible oxidation waves at 0.80and 1.25 V (in CH{sub 3}CN, reference SCE). The EST signal (g = 2.0117) of the radical cation [DC-TAF]{sup +} (in SO{sub 2}(1)) exhibits a five=line hyperfine coupling pattern with a{sub n} = 0.096 mT. DC-TAF forms a series of 1:1 radical ion salts [DC-TAF][X] by electrooxidation in the presence of tetrahedral counterions (X{sup {minus}} = BF{sub 4}{sup {minus}}, ClO{sub 4}{sup {minus}}, FSO{sub 3}{sup {minus}}). The crystal structures of these salts are isomorphous, monoclinic space group P2{sub 1}/n. and consist of one-dimensional ladder-like arrays of [DC-TAF]{sup +} radical cations bridged by S---S contacts ranging from 3.5 to 3.7 {angstrom}. Variable-temperature conductivity and magnetic measurements on [DC-TAF][ClO{sub 4}] indicate Mott insulator behavior, with a measured band gap of 0.30 eV.
- Research Organization:
- Univ. of Arkansas, Fayetteville (US)
- Sponsoring Organization:
- Natural Sciences and Engineering Research Council of Canada (NSERC); National Science Foundation (NSF); USDOE
- DOE Contract Number:
- FG02-97ER45668
- OSTI ID:
- 20000099
- Journal Information:
- Journal of the American Chemical Society, Vol. 121, Issue 28; Other Information: PBD: 21 Jul 1999; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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