The crystal structure and electronic properties of three novel charge transfer co-crystals TCNQFn-triphenylene (n=0, 2, 4)

The pure phase syntheses of three novel organic charge transfer complexes, obtained by combining the polyaromatic hydrocarbon triphenylene with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its fluorinated derivatives, are reported together with their crystal structures determined by 3D electron diffraction. The degree of charge transfer is estimated via examining intramolecular vibrational mode displacements between neutral TCNQF(n) and its complexes with triphenylene using infrared spectroscopy. The direct optical band gaps of 1.87, 1.76 and 1.70 eV for triphenylene-TCNQF(n) (n = 0, 2, 4) respectively, are determined via diffuse reflectance spectroscopy. The application of advanced structure determination techniques in combination with spectroscopic methods has allowed us to shed light on compelling charge transfer systems and to gain indications for the design of improved electrical organic conductors.