Photophysicochemical properties and TD-DFT calculations of a novel terminal alkyne substituted metal free phthalocyanine

The synthesis of a novel free base tetrakis(prop-2-ynyloxy) phthalocyanine (2) is described, along with its characterization by IR, UV-visible absorption, and H-1 NMR spectroscopy and mass spectrometry. The compound exhibited good solubility in a wide range of organic solvents and no significant aggregation was observed over a wide concentration range. The values for the singlet oxygen (Phi(Delta)), photodegradation, fluorescence (Phi(F)) and triplet state quantum yields and the fluorescence and triplet state lifetimes are reported. A relatively high Phi(Delta) value of 0.46 was obtained in DMSO. The ability to carry out "click" chemistry at the ligand periphery enhances the potential utility of 2 for use in bioconjugates in photodynamic therapy (PDT). A moderately high Phi(F) value of 0.18 is observed for emission in the therapeutic window in the near-IR region, which suggests that it may also be possible to determine the level of localization of 2 in tumor cells through bioimaging.