Cation radical salts of cyano(ethylenedithio)tetrathiafulvalene with halogenated anions: annihilation of the CN center dot center dot center dot Hal interaction and stabilisation of conducting, antiferromagnetic square or chain-type salts
T. Devic et al., Cation radical salts of cyano(ethylenedithio)tetrathiafulvalene with halogenated anions: annihilation of the CN center dot center dot center dot Hal interaction and stabilisation of conducting, antiferromagnetic square or chain-type salts, NEW J CHEM, 25(11), 2001, pp. 1418-1424
The synthesis, X-ray crystal structure and electrochemical properties of 3-
cyano-3',4'-ethylenedithiotetrathiafulvalene (EDT-TTF-CN, 1) are described
together with electrocrystallisation experiments in the presence of various
halogenated anions, I-3(-), FeBr4-, InBr4-, AuBr4-, Mo6Br142-, Mo6Cl8Br62-
. X-Ray crystal structures are described for each salt, characterised by a
systematic absence of any short and directional CN . . . Hal interactions,
convincing evidence of the electrostatic character of this interaction, whi
ch is enhanced in the opposite situation where cationic halogenated tetrath
iafulvalenes are associated with cyanide anions such as Ag(CN)(2)(-).This b
ehaviour is further rationalised by atomic population calculations on TTF-C
N and [TTF-CN](.+) which confirm the strong decrease of the negatively char
ged character of the nitrogen atom upon TTF-CN oxidation to [TTF-CN](.+) A
conducting mixed-valence salt is obtained in [1](2)[I-3],which exhibits an
unusual structure with the I-3(-) anions embedded in the organic conducting
layer. All the other salts contain fully oxidised [1](.+) radical cations,
associated into diamagnetic diads in [1][I-3], [1](2)[Mo6Br14][CH3CN](4) a
nd [1](2)[Mo6Cl8Br6][CH3CN](4), into spin chains in the two isostructural [
1][FeBr4]and [1][InBr4]salts and into a quadratic two-dimensional spin syst
em in [1][AuBr4].