An investigation of the excitation and emission properties of fluorescence compounds using DFT and TD-DFT methods
<p class="03Abstract">The density functional theory and time-dependent density functional theory methods were used for investigation of the excitation and emission properties of some fluorophores. The calculations were based on the optimized geometries of ground states and excited states at the B3LYP functional and LanL2DZ basis set. The results clarified the nature of the optical properties of the compounds and agreed well with the experimental data. The approximate values of excitation energies and emission energies of compounds were also identified. The calculated excitation energies were about 0.01 to 0.56 eV higher than experimental values. Meanwhile, the emission energies were from 0.34 to 0.89 eV higher than experimental values. These large errors occurred when there were great variations between the optimized geometries of ground state and excited states. They could be due to the presence of components of solvent in real solution that stabilized the excited states, leading to reduce the excitation and emission energies in the experiments.</p>