A TD-DFT study on triplet excited-state properties of curcumin and its implications in elucidating the photo sensitizing mechanisms of the pigment

In this Letter, we present time-dependent density functional theory (TD-DFT)-derived triplet state properties of curcumin in vacuum, benzene and DMSO. Accordingly, the photosensitizing mechanisms of curcumin are explained. It is revealed that in benzene and DMSO, excited curcumin can react with O-2 to generate O-1(2) and O-2(center dot-) through energy transfer and electron transfer, however, the O(2)(center dot-)generating pathways are different in both solvents. This indicates the potential of TD-DFT in determining the excited-state properties of pigments, which is of significance in getting a deeper insight into the photodynamic mechanisms of photo sensitizers. (c) 2005 Elsevier B.V. All rights reserved.