Search

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. [ABSTRACT FROM AUTHOR]

An anion radical salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with the complex composition (N–Me–DABCO)(TCNQ)2 (1) has been synthesized. The crystal structure 1 has been characterized by X-ray diffraction. The structure of this salt consists of almost homogeneous stacks of TCNQ particles separated by cation layers. Interplanar spacings of 3.25 and 3.29 Å alternate in the stacks. Due to the alternating distances and uniform charge distribution in the stacks, conducting channels are formed in the structure, which determine the properties of an organic metal or a narrow-gap semiconductor, as confirmed by IR spectra containing electron-phonon interaction-related features. In particular, vibrational lines against the continuous absorption background are observed: the band gap does not exceed 0.06 eV. As a result lines of totally symmetric vibrations appear (without the electron-phonon interaction, these lines are forbidden in the IR spectra). [ABSTRACT FROM AUTHOR]

An anion radical salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with the complex composition (N–Me–DABCO)(TCNQ)2 (1) has been synthesized. The crystal structure 1 has been characterized by X-ray diffraction. The structure of this salt consists of almost homogeneous stacks of TCNQ particles separated by cation layers. Interplanar spacings of 3.25 and 3.29 Å alternate in the stacks. Due to the alternating distances and uniform charge distribution in the stacks, conducting channels are formed in the structure, which determine the properties of an organic metal or a narrow-gap semiconductor, as confirmed by IR spectra containing electron-phonon interaction-related features. In particular, vibrational lines against the continuous absorption background are observed: the band gap does not exceed 0.06 eV. As a result lines of totally symmetric vibrations appear (without the electron-phonon interaction, these lines are forbidden in the IR spectra). [ABSTRACT FROM AUTHOR]