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

Electron-withdrawing perfluoroalkyl peripheralgroups 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 offluorination also enhances the reducibility of Pcs and could altertheir singlet oxygen (1O2) photoproduction. The ethanol/toluene20:80 vol % solvent mixture was found to dissolve perfluorinated FnPcZn complexes,n= 16, 52, and 64, and minimize the aggregation of the sterically unencumbered F16PcZn. The1O2production ability of FnPcZn complexes was examined using 9,10-dimethylanthracene (DMA) and 2,2,6,6-tetramethylpiperidine(TEMP) in combination with UV-vis and electron paramagneticresonance (EPR) spectroscopy, respectively. While the photo-reduction of F52PcZn and F64PcZn in the presence of redox-active TEMP lowered1O2production, DMA was a suitable1O2trap forranking the complexes. The solution reactivity was complemented by solid-state studies via the construction of photoelectrochemicalsensors based on TiO2-supported FnPcZn, FnPcZn|TiO2. Phenol photo-oxidation by1O2, followed by its electrochemical reduction,defines a redox cycle, the1O2production having been found to depend on the value ofnand structural features of the supportedcomplexes. Consistent with solution studies, F52PcZn was found to be the most efficient1O2generator. The insights on reactivitytesting and structural-activity relationships obtained may be useful for designing efficient and robust sensors and for other1O2-related applications of FnPcZn

Automated summary

Electron-withdrawing perfluoroalkyl peripheral groups grafted on phthalocyanine macrocycles improve their properties for catalytic applications, with a high degree of fluorination enhancing reducibility and potentially altering singlet oxygen photoproduction. The use of a specific solvent mixture was found to dissolve perfluorinated complexes and minimize aggregation, while solid-state studies showed potential for developing efficient sensors based on these complexes. The most efficient generator of singlet oxygen was determined to be F52PcZn, highlighting the importance of the value of n and structural features in their applications.