ADVANCEMENTS IN PORPHYRIN SENSITIZED PHOTOELECTROCHEMICAL CELLS FOR TEMPO OXIDATION

Porphyrin sensitizers play a pivotal role in the development of dye-sensitized photoelectrochemical (DSPEC) devices thanks to their strong UV-Vis absorption, excellent electrochemical and photochemical stability, and adjustable electronic properties through structural modifications.[1] By carefully tuning the porphyrin structure, the ground-state potential of the sensitizers can be optimized to facilitate photo-oxidation processes at the anodic counterpart of DSPEC devices as for hydrobromic acid[2] and water splitting.[3] This crucial attribute can be attained by incorporating electron-withdrawing groups as fluorine atoms into the porphyrin core, inducing a significant electron deficiency. Recently, the implementation of porphyrin sensitizers in the oxidation of the stable organic radical 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) has gained significant attention.[4] In this contribution, we report a novel series of perfluorinated ZnII-porphyrin-based sensitizers specifically tailored for TEMPO oxidation (Figure 1). A4 β-pyrrolic and A3B meso-substituted zinc porphyrins, equipped with both donating amine groups and π-accepting spacers to optimize donor-acceptor interactions, are investigated. The impact of the molecular design of porphyrins on electronic properties is comprehensively explored through a combination of electrochemical, spectroscopic, computational, and photophysical analyses. The key parameters which govern the performances of porphyrin-based DSPEC devices for TEMPO oxidation are also evaluated. The insights gained from these studies pave the way for the development of efficient and stable DSPEC systems for energy conversion and storage applications.