Synthesis, characterization, electrochemistry and VOC sensing properties of novel ball-type dinuclear metallophthalocyanines

Abstract

New homodinuclear ball-type Cu(II)-Cu(II) 4, Zn(II)-Zn(II) 5, and Co(II)-Co(II) 6 phthalocyanines were synthesized from 4,4'-(9H-fluorene-9-yl-dimethoxy)diphthalonitrile 3, which was obtained by the reaction of 4-nitrophthalonitrile 2 with 9H-fluorene-9,9-dimethanol 1. The compounds were characterized by elemental analysis, UV/vis, IR, H-1 NMR, C-13 NMR and MALDI-TOF mass spectroscopies. Electrochemical and spectroelectrochemical measurements suggested that ball-type phthalocyanine compounds 4-6 form stable mixed-valence species in nonaqueous medium, as a result of the remarkable intramolecular interactions between the two metallophthalocyanine units. Ball-type cobalt phthalocyanine complex, 6 showed high catalytic activity toward dioxygen reduction. Temperature dependence of direct current (dc) conductivity of the films of 4-6 in the range of 295-523 K displayed their semiconductor behavior. Alternating current (ac) conductivity measurements (40 Hz-100 kHz) showed that dominant conduction mechanism for 4-6 can be modeled depending on temperature and frequency. Gas sensing properties of the thin films of 4-6 toward volatile organic compounds (toluene, chloroform, and acetone) at room temperature were good with reversible response. The best sensitivities were obtained with the film of 6 for the vapors of toluene (250 ppm), acetone (150 ppm), and chloroform (1500 ppm) with the values of 1.3 x 10(-1), 1.6 x 10(-2), and 2.1 x 10(-2) ppm(-1), respectively