Correlation between the Fluorination Degree of Perfluorinated Zinc Phthalocyanines, Their Singlet Oxygen Generation Ability, and Their Photoelectrochemical Response for Phenol Sensing.

Electron-withdrawing perfluoroalkyl peripheral groups grafted on phthalocyanine (Pc) macrocycles improve their single-site isolation, solubility, and resistance to self-oxidation, all beneficial features for catalytic applications. A high degree of fluorination also enhances the reducibility of Pcs and could alter their singlet oxygen (O) photoproduction. The ethanol/toluene 20:80 vol % solvent mixture was found to dissolve perfluorinated FPcZn complexes, = 16, 52, and 64, and minimize the aggregation of the sterically unencumbered FPcZn. The O production ability of FPcZn complexes was examined using 9,10-dimethylanthracene (DMA) and 2,2,6,6-tetramethylpiperidine (TEMP) in combination with UV-vis and electron paramagnetic resonance (EPR) spectroscopy, respectively. While the photoreduction of FPcZn and FPcZn in the presence of redox-active TEMP lowered O production, DMA was a suitable O trap for ranking the complexes. The solution reactivity was complemented by solid-state studies via the construction of photoelectrochemical sensors based on TiO-supported FPcZn, FPcZn|TiO. Phenol photo-oxidation by O, followed by its electrochemical reduction, defines a redox cycle, the O production having been found to depend on the value of and structural features of the supported complexes. Consistent with solution studies, FPcZn was found to be the most efficient O generator. The insights on reactivity testing and structural-activity relationships obtained may be useful for designing efficient and robust sensors and for other O-related applications of FPcZn.