Synthesis, electrochemical and photophysical studies of axially substituted quarternizable titanyl phthalocyanines

This work reports on the synthesis, characterization, photophysical properties and electrochemical characterization of new tetra-substituted titanium phthalocyanine with dimethylaminoethanol groups on peripheral positions (2) and water-soluble quaternized counterpart. The water-soluble titanium(IV) phthalocyanine derivative (3) was found to be aggregated in aqueous media but was partially or fully disaggregated in the presence of a surfactant Triton X-100. The capping of the titanyl (metaloxo) inner core with catechol derivatives (4–7) were also synthesized. The axially substituted titanium phthalocyanines show high solubility and a low aggregation tendency due to the steric hindrance. The structures of these compounds were characterized by using elemental analyses, UV–Vis, FT-IR, 1H NMR and mass spectroscopies. Their photophysical properties were also studied and fluorescence quantum yields were found to range from 0.02 to 0.13. The electrochemical properties of 2 were also investigated by using cyclic voltammetry in this report.

Graphical abstractThe synthesis, characterization, photophysical properties and electrochemical characterization of new tetra-substituted titanium phthalocyanine with dimethylaminoethanol groups on peripheral positions, water-soluble quaternized counterpart and the capping of the titanyl (metaloxo) inner core with catechol derivatives were synthesized for the first time in this study. Photophysical and photochemical studies were carried out in order to determine the potential of the complexes as photosensitizers for use in photodynamic therapy.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Titanyl phthalocyanine and axially substituted derivatives have been synthesized. ► Water soluble quaternized TiOPc has been synthesized. ► The fluorescence quantum yield is highest for TiOPc (2). ► Randles-Sevcik equation was used to determine diffusion coefficients. ► Kinetic parameters were determined for a deeper investigation on electron transfer mechanisms.