The regularity of Raman spectra of fluorine carotenoids isomers modulated by polarization environment

Abstract The fluorine atom serves as a valuable nuclear magnetic resonance (NMR) label due to its compact size, making it an effective substitute for hydrogen atoms. While the high electronegativity of fluorine can alter certain properties of the substrates to which it is attached, its judicious application has the potential to impart desirable new characteristics. In this paper, the effects of fluorine atom on the electronic and optical properties of π conjugated molecules in polar environment were studied by taking fluorine substituted canthaxanthin and β -carotene as examples. In the solution system, with the increased of the polarity of the local environment, affected by the solvent induced dipole effect, taking the stretching vibration of carbon–carbon double bond as an example, the Raman peak intensity increased, the wave number decreased, and the peak splitting occurred in the strong polar environment. The sensitivity of polarizability to environment of canthaxanthin was higher than that of β -carotene, and the sensitivity of polarizability to environment of 13-cis configuration was higher than that of 9-cis configuration. In most cases, the substitution of fluorine atoms lowers the vibrational energy levels, causing the Raman peaks to shift to lower wavenumbers, but this trend can be influenced by the spatial structure of the end groups and the carbon backbone. For the frontier molecular orbital, the fluorine atom of the substituted trifluoromethyl showed a small number of lone pair electronic orbital characteristics, which made a small contribution to the molecular orbital transition.