Structural relations in (1:1) and (2:1) Cyanobenzene-Ethylenedithio-TTF radical salts; The role of C≡N…H interactions.
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), 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 compounds present dimerization of the donor units. Compounds 1 and 2 are isomorphous with a crystal structure characterized by slipped head to tail donor dimers stacks segregated from anions columns. Compounds 3 and 4 are also 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 C≡N…H pairing interactions associated with R22(8), R24(8), R22(10), R24(10) synthons between donors in nearby dimers. 3 and 4 are semiconductors, and their magnetic susceptibility exhibit 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]-.