Crystal Structure of Anion-Radical Salts of 7,7,8,8-tetracyanoquinodimethane with N-xylyl-pyridinium and N-xylyl-isoquinolinium Cations

Novel anion-radical salts of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with N-xylyl-pyridinium and N-xylyl-isoquinolinium cations of complex composition ((N-Xy-Py)(TCNQ)(2)(CH3CN) (1) and (N-Xy-iQn)(TCNQ)(2) (2), respectively) have been synthesized. The crystal and molecular structures of 1 and 2 are determined using X-ray diffraction (XRD) analysis. Salts are crystallized into different systems: the (N-Xy-Py)(TCNQ)(2)(CH3CN) structure belongs to the orthorhombic system, while the (N-Xy-iQn)(TCNQ)(2) structure belongs to the triclinic system. Crystals of salt 1 contain dimerized stacks of anion-radicals of the ABAB type, while the stacks in structure 2 are tetramerized. This structural distortion does not facilitate high electrical conductivity, which is confirmed by the IR spectral data: the spectra of salts 1 and 2 do not exhibit any specific features of high-conductivity TCNQ salts (continuous absorption and anomalous line broadening). This fact can be caused by the Peierls instability, which induces dimerization of stacks in crystals of salt 1 and tetramerization of stacks in crystals of salt 2.