Synthesis, Characterization, and Electrochemical and Electrical Properties of Novel Pentaerythritol‐Bridged Cofacial Bismetallophthalocyanines and Their Water‐Soluble Derivatives

Abstract

AbstractNovel cofacial bismetallophthalocyanines and theirwater‐soluble derivatives were prepared. The precursor4,4′‐(2‐phenyl‐1,3‐dioxane‐5,5‐diyl)bis(methylene)bis(oxy)diphthalonitrile 3 was obtained by the reaction of [5‐(hydroxymethyl)‐2‐phenyl‐1,3‐dioxan‐5‐yl] methanol 1 and 4‐nitrophthalonitrile 2 with K2CO3 in DMF at 50 °C. Cyclotetramerization was achieved by heating the homogenized mixture of the precursor, bisphthalonitrile, and Zn(OAc)2·2H2O or Co(OAc)2·4H2O at 300 °C, which was followed by catalytic hydrogenation of the resulting product with Pd/C(10 %) in DMF. The target water‐soluble phthalocyanines were acquired from boiling suspensions of the compounds bearing eight OH side groups in aqueous KOH (20 %) solution. The structure of the target compounds was confirmed by elemental analysis, FTIR, UV/Vis, 1H NMR, ICP‐MS, and MALDI‐TOF spectroscopic methods. The electrochemical and spectroelectrochemical measurements suggested the formation of various mixed‐valent oxidation and reduction species, as a result of the strong intramolecular interactions between the two cofacial phthalocyanine units in the compounds. Impedance spectroscopy, dc conductivity, and thermopower measurements were performed using spin‐coated films of these compounds as a function of temperature (290–440 K) and frequency (40–105 Hz). Dc conductivity showed typical Arrhenius behavior for all compounds. At low temperatures, a curved line was observed for the complex plane plots of impedance for all phthalocyanines. These curved lines transformed into a full semicircle with increasing temperature. The dependency of frequency exponent s on temperature suggested hopping‐type conduction. A positive Seebeck coefficient was observed for all compounds, which indicates that the compounds behave as a p‐type semiconductor. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)