The first BETS radical cation salts with dicyanamide anion: Crystal growth, structure and conductivity study

Electrochemical oxidation of bis(ethylenedithio)tetraselenafulvalene (BETS) has been investigated. Simple and complex dicyanamides of transition metals (Mn2+, Ni2+ and Fe2+) were used as electrolytes. The correlation between composition of prepared radical cation salts and metal nature in electrolytes was established. Manganese dicyanamides provide the formation of BETS salts with the {Mn[N(CN)2]3}- and [N(CN)2]-XH2O anions. When Ni- or Fe-containing electrolytes were used only metalless BETS salts, α″-BETS2[N(CN)2]·2H2O (I) and θ-BETS2[N(CN)2]·3.6H2O (II), formed. Structures and conducting properties of these salts were analyzed. Both salts exhibit layered structure. Conducting radical cation layers have α″ (I)- or θ-type (II). Anion sheets appear as two-dimensional polymer networks of different types. These networks are formed by [N(CN)]2− anions and water molecules interlinked by hydrogen bonds. Salt I is a semiconductor and II demonstrates resistance drop down to150 K at normal pressure and down to 72 K at ∼0.4 kbar pressure.