Synthesis, characterization, electrochemical and CO₂ sensing properties of novel mono and ball-type phthalocyanines with four phenolphthalein units

The novel mono metallo [Zn(II) 4 and Co(II) 5] and ball-type or cofacial bis-metallo [Zn(II) 6 and Co(II) 7] phthalocyanines have been synthesized from 3, which can be obtained by the reaction of 4-nitrophthalonitrile 1 with 3,3-bis(4-hydroxy-phenyl)isobenzofuran-1(3H)-one 2 (phenolphthalein). The phthalocyanines have been characterized by elemental analysis, UV-vis, IR, ¹H NMR, and mass spectroscopy. The redox behavior of the complexes was investigated by cyclic voltammetry and controlled-potential coulometry. The electrochemical measurements suggested the formation of mixed-valent species during the redox processes of bis-metallophthalocyanines 6 and 7, as a result of the intramolecular interactions between two cofacial Pc units. The effect of temperature on the CO₂ sensing properties of a spin-coated thin film of 7 was also investigated.