Synthesis of asymmetrically substituted push-pull phthalocyanines as potential photodynamic therapy agent

Abstract

Over the past decade, photodynamic therapy (PDT) has begun to gain worldwide attention either as a primary or as an alternate treatment for solid cancers.1The success of the treatment largely depends upon the tumor-selectivity and photosensitizing properties of the photosensitizer used. Phthalocyanines with absorption extending well into the near-IR region have been considered to be potential PDT agents. In the present study, the synthesis of asymmetrically substituted phthalocyanine has been described. In order to avoid the tedious separation of a mixture of phthalocyanines prepared by statistical method, Kobayashi’s ring expansion of boron subphthalocyanine route2 has been used. This route produces exclusively 3:1 asymmetrical phthalocyanine. Fluorinated boron subphthalocyanine and diiminoisoindoline of glycol chain substituted phthalonitrile were used as reagents. Mild reaction conditions were employed using dimethylaminoethanol as the solvent. The compound has been characterized by optical absorption and emission (steady-state and time-resolved), ¹H and ¹⁹F NMR, and mass spectroscopic analysis. Studies on singlet oxygen yield and other studies are in progress.