A study of the low-lying singlet and triplet electronic states of chlorophyll a and b

Chlorophylls have been extensively investigated both experimentally and theoretically owing to the fact that they are essential for photosynthesis. In the reported study, two forms of chlorophyll, chlorophyll a and chlorophyll b, were investigated by means of the density functional theory. Optimization of the S0, S1 and T1 states was performed with the B3-LYP functional. The computed fluorescence lifetimes show good agreement with available experimental data. The electronic adiabatic energies of S1 and T1 states are 2.09/2.12 and 1.19/1.29 eV for chlorophyll a and chlorophyll b, respectively. The implications of these results on triplet formation are discussed. In addition, the calculated vertical ionization potentials showed good agreement with the experimental results.