Synthetic conducting materials X. Synthesis and characterization of charge-transfer complexes of derivatives of 1,10-phenanthroline and TCNQ

Abstract

A series of 2-, 9-substituted or disuubstituted derivatives of 1,10-phenanthroline has been synthesized by chlorination or oxidation. The charge-transfer complexes of these 1,10-phenanthroline derivatives with 7,7,8,8-tetracyanoquinodimethane (TCNQ) have been prepared and characterized by elemental analysis, infrared, electronic and mass spectroscopy. The ratio of TCNQ to TCNQ− was determined by electronic absorption spectra. The degree of charge transfer was estimated by cyano stretching, external C=C stretching and CH bending frequency in complexes. The physical state and properties of unpaired electrons in charge transfer complexes were investigated by magnetic susceptibility measurement and electron paramagnetic resonance spectra in variable temperature condition from room temperature to 77K. The magnetic susceptibility data show that the numbers of electrons in complexes are from 8.4% to 92.4% per molecule. These results show that these complexes are either in the molecular complex or simple salt form crystal. The variable temperature electric conductivity measurement show that the conductivity of these complexes are in the range of 10−2 to 10−8 S cm−1 at room temperature with activation energy of 0.11 to 0.73 eV. The structure of MPO-TCNQ has been determined by single crystal x-ray diffractometry which has P21/c space group with a=7.9625(16), b=7.2914(09), c=34.1257(16) and Beta=90.20(2).