Structural relations in (1 : 1) and (2 : 1) cyanobenzene-ethylenedithio-TTF radical salts; the role of CN⋯H interactions

Abstract

Four salts of the dissymmetric TTF-derivative 4-cyanobenzene-ethylenedithio-tetrathiafulvalene (4-CNB-EDT-TTF) with different anions, namely (4-CNB-EDT-TTF)A with A = ClO₄ (1), BF₄ (2) and (4-CNB-EDT-TTF)₂[M(mnt)₂] with M = Ni (3) and Au (4), were obtained by electrocrystallization and characterized by single-crystal X-ray diffraction, magnetic susceptibility and electrical conductivity measurements in comparison with the analogues based on the donor 5-CNB-EDT-TTF. All the compounds present dimerization of the donor units. Compounds 1 and 2 are isomorphous with a crystal structure characterized by slipped head to tail donor dimer stacks segregated from anion columns. Compounds 3 and 4 are isostructural with a crystal structure characterized by alternated stacks of head to tail donor dimers and acceptors. In spite of the different structural types and stoichiometries, all of these compounds have CN⋯H pairing interactions associated with R²₂(8), R²₄(8), R²₂(10), and R²₄(10) synthons between donors in nearby dimers. 3 and 4 are semiconductors, and their magnetic susceptibility exhibits a behaviour typical of antiferromagnetically coupled spin chains with magnetic exchange values J/k = −149.9 and −60.1 K, respectively, and in the case of 3, a Curie–Weiss contribution from the paramagnetic anions [Ni(mnt)₂]⁻.