First Planar Binuclear Phthalocyanines Sharing a Common Carbazole Linkage: Synthesis, Optical and Photochemical Properties

Abstract

Abstract The first examples of planar binuclear phthalocyanines sharing a common carbazole unit were obtained using indirect and direct mixed cyclization approaches. The synthetic route to the starting 9-benzylcarbazole-2,3,6,7-tetranitrile was reconsidered and literature conditions were successfully optimized. In addition to the binuclear complex, a low-symmetry A3B phthalocyanine with free cyano groups was isolated and identified. Accurate assignment of absorption bands in the UV-Vis spectra was performed using magnetic circular dichroism and simplified TD-DFT calculations. The target binuclear complexes demonstrate the ability of singlet oxygen generation, with ΦΔ values reaching 0.15 for the tert-butyl-substituted compound. The products of photodegradation were studied using mass spectrometry and UV-Vis spectroscopy. Electrochemical and spectroelectrochemical studies showed a gradual oxidation of the macrocycle, accompanied by the interruption of an extended binuclear π-system.