Polymorphism and Metallic Behavior in BEDT-TTF Radical Salts with Polycyano Anions

Up to five different crystalline radical salts have been prepared with the organic donor BEDT-TTF and three different polynitrile anions. With the polynitrile dianion tcpd 2？ (=C[C(CN) 2] 3 2？), two closely related radical salts: α'-(ET) 4tcpd·THF ( 1) (THF = tetrahydrofurane) and α'-(ET) 4tcpd·H 2O ( 2) have been prepared, depending on the solvent used in the synthesis. With the mono-anion tcnoetOH ？ (=[(NC) 2CC(OCH 2CH 2OH)C(CN) 2] ？) two polymorphs with similar physical properties but different crystal packings have been synthesized: θ-(ET) 2(tcnoetOH) ( 3) and β''-(ET) 2(tcnoetOH) ( 4). Finally, with the mono-anion tcnoprOH ？ (=[(NC) 2CC(OCH 2CH 2CH 2OH)C(CN) 2] ？) we have prepared a metallic radical salt: β''-(ET) 2(tcnoprOH)(CH 2Cl 2CH 3Cl) 0.5 ( 5). Salts 1？ 4 are semiconductors with high room temperature conductivities and activation energies in the range 0.1–0.5 eV, whereas salt 5 is metallic down to 0.4 K although it does not show any superconducting transition above this temperature.