Enhanced Visible Light Absorption and Photophysical Features of Novel Isomeric Magnesium Phthalocyaninates with Cyanophenoxy Substitution

Abstract

Novel metal-free and Mg(II) [3/4-(3,4-dicyanophenoxy)phenoxy]-substituted phthalocyanines were obtained and characterized using NMR, IR, UV-vis spectroscopy, and mass spectrometry. This substitution provided compounds with good solubility in organic media, and thus their spectroscopic and fluorescent properties were studied. The formation of the investigated phthalocyanine complexes with central magnesium ions led to the stabilization of macrocyclic molecules in solution, preventing aggregation through specific and universal solvation. From meta-substitution to para-substitution, insignificant spectroscopic changes were observed. The complexes exhibited higher values of molar light absorption coefficients and fluorescence quantum yields (up to 55%) compared to ligands. The efficiency of both the fluorescence-quenching and singlet oxygen generation processes in the case of magnesium [3/4-(3,4-dicyanophenoxy)phenoxy]phthalocyaninates was found to exceed that of the unsubstituted zinc phthalocyaninate, which suggests the potential applicability of these compounds as PDT sensitizers.

Keywords

• phthalocyanines
• complexes
• photochemistry
• singlet oxygen