First radical cаtion salt of bis(ethylenedithio)tetrathiafulvalene with organic anion [С(NCN)2NH2]–: synthesis, structure, and conducting properties

Abstract

The electrochemical oxidation of bis(ethylenedithio)tetrathiafulvalene (ET) in the presence of simple dicyanamide salts of rare-earth metals with the general formula M[N(CN)₂]₃ (M = Gd³⁺, Dy³⁺, and Ho³⁺) as electrolytes was studied for the first time. A novel radicalcаtion salt α-ЕТ₂[С(NCN)₂NH₂] with the unexpected (2,1-dicyano)guanidine anion was synthesized. The crystal structure of the salt and its conducting properties were studied. The structure of the salt is layered with alternating conducting radical-cation and insulating anionic layers. The cationic layers of the α-type are formed by two crystallographically independent radical-cations of ET of various charges. The anionic layers are formed of [С(NCN)₂NH₂]^– anions linked by hydrogen contacts into chains. The crystals of ЕТ₂[С(NCN)₂NH₂] demonstrate a semiconducting character of conductivity in a temperature range of 300—100 K.