Photoreduction and light-induced triplet-state formation in a single-site fluoroalkylated zinc phthalocyanine

Abstract

Electron-withdrawing perfluoroalkyl peripheral substituents enhance the photosensitizing properties of metal phthalocyanines while increasing their solubility, thus providing opportunities for advanced characterization of their catalytically-relevant excited states. Optical absorption and electron paramagnetic resonance (EPR) spectroscopy experiments reveal that red light induces the reduction of perfluoroisopropyl-substituted zinc(II) phthalocyanine (F₆₄PcZn) dissolved in ethanol. A similar photoreduction does not occur in toluene. Furthermore, intense UV irradiation causes the photodegradation of F₆₄PcZn in ethanol, but low power UV illumination favours the formation of the triplet excited state, a prerequisite for new photocatalytic applications. The UV-induced triplet state of F₆₄PcZn is characterized using a combination of transient EPR experiments and DFT computations.