How does the β-ionone effect the spectra of chlorophyll and the excitation energy transfer in solution

Abstract

This paper presents the excitation spectra and fluorescence spectra of mixed solution containing chlorophyll a(Chla), chlorophyll b(Chlb) and β-ionone of different concentration, investigates the spectral changes of Chla and Chlb caused by β-ionone through optimizing the frontier orbital of Chl-β-ionone compound, and calculates the energy transfer rate between Chla and Chlb by means of the fluorescence Gauss decomposition. The results show that the β-ionone interacts with Chl mainly via the connection between the magnesium atom in Chl molecule and the carbonyl in β-ionone molecule. The formation of Chl-β-ionone compound changes the charge distribution of Chl so greatly that it leads to the red-shift of the excitation spectra and blue-shift of the fluorescence spectra of Chls. Also in the compound the electronic energy located on carbon double bond of β-ionone can be transferred to Chl molecule by the Mg…O bond, which enhances the fluorescence intensity greatly. The calculation of the excitation energy transfer (EET) rate indicates that a small amount of β-ionone can promote the EET between Chla and Chlb.