Electronic and structural properties of novel cyanocarbon dyes based on tetracyanoethylene

Four novel cyanocarbon dyes derived from tetracyanoethylene (TCNE) have been studied. They are carbanions isolated as tetraphenylarsonium salts of formula C 11N 7H 2 - (1), C 15N 6H 3 - (2), C 14N 7H 2 - (3), and C 13N 8H - (4). Compound (1) was obtained by a condensation reaction of TCNE promoted by Ti(bpy) 3 and its structure has already been reported. Compounds (2)-(4) are the 1,3-bistricyanovinyl derivatives of cyclopentadienyl, pyrrolyl, and imidazolyl anions, respectively. The tetraphenylarsonium salt of anion (3) gives crystals isomorphous with the crystals of the analogous salts of anions (2) and (4), whose crystal structures are reported here. Structural and electronic properties of the four anions are discussed on the basis of 13C n.m.r., i.r., u.v., and electrochemical data; electrical and magnetic properties of their radical salts with the tetrathiafulvalenium cation (TTF .+) are also reported and discussed.