Exploring the solvent regulated electron status properties of astaxanthin by Raman spectroscopy and DFT simulation

Astaxanthin (AST) is a carotenoid, whose configuration that can be regulated by changing the solvent environment is responsible for their specific photophysical properties. This study investigates the ground and excited states characteristics of AST through Raman and absorption spectra in solvents with varying polarizabilities. The red-shift observed in the Raman and absorption spectra confirms an increase conjugation extent in the AST molecule. Higher polarizability solvent enhances the extent of intramolecular charge transfer (ICT) increases the probability of electronic transitions in the excited state. When Rn≥0.273, the Huang-Rhys factor and the electron phonon coupling (EPC) coefficient significantly diminishes. These results suggest that higher solvent polarizability reduces the energy gap and enhances electron delocalization. Desity functional theory (DFT) simulations provide characteristics detailed of ICT within different segments in the excited state.