Structures and physical properties of radical cation salts based on alkyloxytetracyanoallylide anion

Various radical cation salts of a series of 2-alkyloxytetracyanoallylide anions (RO-TCA; R=Me, Et, Pr, Bu) were investigated to examine the structure-property relationship. TTT salts were classified into three groups based on their crystal and elctronic structures which were essentially determined by the stoichiometries; 3:2, 1:1 and 1:2. The crystal structures of 7 TTT salts were solved, which contained the first examples of TTT2+ structure. BEDT-TTF salts of α′ and β″ type were obtained. All the a′ type salts were semiconducting, however, MeO-TCA salt turned into a metallic one after keeping it for a month at room temperature or for a day at 330 K. RO-TCAs possess structural flexibility, which is essential to provide multiple stoichiometries and similar packing motives of donor.