Water soluble quarternizable gallium and indium phthalocyanines bearing quinoline 5-sulfonic acid: Synthesis, aggregation, photophysical and electrochemical studies

In this work, we have presented the synthesis, characterization, photophysical properties and electrochemical characterization of new tetra α and β-substituted indium and gallium phthalocyanines MPcX(α- or β-HQSA)₄ {M = Ga(III) (3) (4) and In(III) (5) (6); X = Cl} attached with 1-hydroxy quinoline-5-sulfonic acid groups on non-periphery and their water-soluble quaternized counterpart. The non-periphery substituted phthalocyanines with axially counter chlorine anion exhibit high solubility and low aggregation tendency owing to bulky HQSA steric hindrance moieties. The novel phthalocyanine precursors, 3, 4, 5, 6 synthesis, characterization, photochemical properties (singlet oxygen quantum yields and photodegradation quantum yields) and photophysical properties (fluorescence quantum yields and flouresans behavior) of their peripherally tetra substituted gallium and indium phthalocyanines are reported in this study. The new compounds (3, 4, 5, 6) have been characterized by using spectroscopic methods, FT-IR, ¹H NMR spectroscopy, electronic spectroscopy and Maldi-TOF spectra in addition to elemental analysis. General trends focus on fluorescence, photodegradation and singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO), water (H₂O). The nature of the substituent and solvent effect on the photophysical and photochemical parameters of the substituted phthalocyanines (3, 4, 5, 6) are also reported. The effect of point of substitution on the electrochemical properties of newly synthesized phthalocyanine compounds, periphery (β-) and non-periphery (α-) substituted with 8-hydroxyquinoline-5-sulfonic acid group were evaluated.