Variety of BEDT-TTF salts with organic polycyano anions

Cation radical salts based on BEDT-TTF (ET) with 1,1,2,4,5,5-hexacyano-3-azapentadienide (HCAPD−) and a series of 2-alkyl-1,1,3,3-tetracyanoallyl anions (R–TCA−; R=MeS, MeNH, NH2) were investigated. HCAPD− provided 1:1 (D:A) (1) and 2:1:0.5 (THF) (2) salts. Although 1 consists of ladder-like structures, the strong dimerization of ET+ molecules results in a non-magnetic state. 2 shows a semiconductor–semiconductor transition near 200 K. Magnetic susceptibility of 2 shows a peculiar behavior. R–TCA− anions provided 2:1 salts. MeS– and MeNH–TCA− salts are metallic, though NH2–TCA− salt is regarded as a Mott insulator.