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 ( 1 O 2 ) photoproduction. The ethanol/toluene 20:80 vol % solvent mixture was found to dissolve perfluorinated F n PcZn complexes, n = 16, 52, and 64, and minimize the aggregation of the sterically unencumbered F 16 PcZn. The 1 O 2 production ability of F n PcZn 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 F 52 PcZn and F 64 PcZn in the presence of redox-active TEMP lowered 1 O 2 production, DMA was a suitable 1 O 2 trap for ranking the complexes. The solution reactivity was complemented by solid-state studies via the construction of photoelectrochemical sensors based on TiO 2 -supported F n PcZn, F n PcZn|TiO 2 . Phenol photo-oxidation by 1 O 2 , followed by its electrochemical reduction, defines a redox cycle, the 1 O 2 production having been found to depend on the value of n and structural features of the supported complexes. Consistent with solution studies, F 52 PcZn was found to be the most efficient 1 O 2 generator. The insights on reactivity testing and structural-activity relationships obtained may be useful for designing efficient and robust sensors and for other 1 O 2 -related applications of F n PcZn.