Enhancing chlorophyll stability by regulating charge transfer in chlorophyll self-aggregation

Chlorophyll (Chl), a natural pigment with broad applications in food systems, faces challenges due to its instability under light exposure. This study explores the relationship between solvent polarity, charge transfer (CT) in Chl self-aggregation, and photostability enhancement. By adjusting ethanol/water ratios (10–100% ethanol), environmental polarity was modulated to investigate its impact on CT dynamics using fluorescence spectroscopy, conductivity analysis, and quantum chemistry calculations. Results demonstrated that higher solvent polarity significantly strengthened CT interactions between Chl molecules, primarily mediated by porphyrin rings, while the hydrophobic phytyl tail influenced aggregate configurations and indirectly modulated CT pathways. Light stability tests revealed that Chl retention in high-polarity solvents (10%–40% ethanol) surpassed low-polarity groups (60%–90% ethanol) by 213.04% and 302.61% on days 4 and 8, respectively, highlighting the critical role of CT-driven aggregation in mitigating photodegradation. Quantum calculations further elucidated that phytyl tail removal altered CT efficiency depending on porphyrin spacing: in 'sandwich' dimers, phytyl absence enhanced CT, whereas in 'face-to-face' configurations, partial removal optimized electron redistribution. These findings underscore solvent polarity as a key regulator of CT-mediated aggregation, offering a mechanism to stabilize Chl through non-covalent interactions. The study advances the understanding of Chl aggregation mechanisms and proposes physical strategies, such as electric-field-induced CT modulation, to enhance the stability of photosensitive natural pigments in food processing and storage.