Abstract
The quantum-chemical method is a crucial area of innovation for photodynamic therapy. Density Functional Theory can be used to investigate the electronic structures, excited states, and other photochemical properties of a photosensitizer. In the present study, the intensities and energies of electronic transitions are calculated, and absorption and vibrational spectra of two photosensitizers, protoporphyrin IX and pyropheophorbide-a are simulated. The calculation proved the experimental results of the fact that pyropheophorbide-a exhibits the intense absorption of Qx at longer wavelength than protoporphyrin IX, and absorption intensity is higher than protoporphyrin IX. Additionally, the influence of solvent models on IR-spectra calculation is studied. This study can lead to the design of new photosensitizers to improve PDT efficiency.