Structural relations in (1 : 1) and (2 : 1) cyanobenzene-ethylenedithio-TTF radical salts; the role of CN⋯H interactions. Issue 48 (25th November 2019) - Lopes, Gonçalo
Abstract : Radical cation salts of 4-CNB-EDT-TTF presenting CN⋯H pairing interactions, semiconducting properties and chains of antiferromagnetically coupled donor dimers. 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 CN⋯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 ] − .