Synthesis, characterization, OFET and electrochemical properties of novel dimeric metallophthalocyanines

Abstract

The synthesis of 4,4′-[6,6′-methylenebis (2-(2-(3,4-dicyanophenoxy)-5-methylbenzyl)-4-methyl-6,1-phenylene)] bis (oxy) diphthalonitrile 1 was achieved starting from 4-nitrophthalonitrile and 6,6′-methylenebis(2-(2-hydroxy-5-methylbenzyl)-4-methylphenol in DMF at 50 °C by the catalysis of K₂CO₃ under argon. The corresponding dimeric metallophthalocyanines (Zn₂Pc₂2 and Co₂Pc₂3) were tetramerized in dimethylaminoethanol with the appropriate metal salt. Newly synthesized compounds were characterized by elemental analysis, UV-vis, FT-IR (ATR), MALDI-TOF mass and ¹H-NMR spectroscopy techniques. The electrochemical properties of the complexes were examined by cyclic voltammetry, differential pulse voltammetry, controlled potential coulometry and in situ spectroelectrochemistry in nonaqueous media. The results showed that while there is considerable weak interactions between the two metal phthalocyanine units in dimeric zinc phthalocyanine, these interactions in dimeric cobalt phthalocyanine is remarkable. The catalytic performances of dimeric cobalt phthalocyanine in the reduction of oxygen in a medium similar to the working conditions of the polymer electrolyte membrane fuel-cells were found to be much higher than that of dinuclear zinc phthalocyanine. Solution-processed films of the complexes were utilized as an active semiconducting layer in the fabrication of organic field-effect transistors (OFETs) in the bottom-gate configurations. The output characteristics of the resulting p-type OFET devices were investigated to evaluate the performances such as the field effect mobility (μ_F). A relatively high field effect mobility of 7.3 × 10⁻³ cm² V⁻¹ s⁻¹ was observed for dimeric cobalt phthalocyanine.