Fluorination pattern-dependent control of electronic properties in Zn(II)-porphyrins: A combined experimental and theoretical investigation

Fluorination is a powerful strategy for tuning the electronic structure and photophysical properties of porphyrins, thereby improving performance in sensing, catalysis, and biomedical applications. In this work, we present a combined experimental and computational investigation of how meso-phenyl versus β-pyrrolic fluorination pattern modulates the optical and redox properties of Zn(II) porphyrins. Commercially available ZnTPP is used as a benchmark, and compared to its meso-perfluorinated analog ZnTPP-F 20 , and β-octafluorinated derivative ZnTPP-βF 8 . UV–Vis absorption and emission measurements, and electrochemical data reveal progressive hypsochromic shifts and systematic stabilization of frontier orbitals upon fluorination, with β-substitution producing the largest optical gap and strongest electrochemical LUMO stabilization. Population analyses and geometry optimizations performed at the M06-2X level, together with TD-DFT calculations using B3LYP, M06-2X, and CAM-B3LYP, consistently reproduce the experimental trends. The results show that meso-perfluorination primarily induces inductive electronic effects transmitted through the phenyl rings, whereas β-fluorination combines strong electron withdrawal with steric distortion of the macrocycle, reducing conjugation and amplifying its impact on excited-state energies. Overall, this study establishes clear structure–property relationships for fluorinated Zn(II) porphyrins and identifies β-fluorination as a particularly effective strategy for tuning LUMO energies, electron affinities, and photophysical responses.