DFT study of five naphthalimide derivatives: Structures and redox properties

Abstract

Geometries for five naphthalimide (NI) derivatives proposed as photoactive redox units in cancer treatment, have been optimized in the ground state, reduced and oxidized states using density functional theory (DFT) with the B3LYP hybrid functional and the 6-31G (d,p) basis set. The bond lengths of the N-[3-(dimethylamino)propyl]-1,8-naphthalimide derivative showed the most variation from the other four NI derivatives due to the nature of its substituent. An examination of atomic charges and spin densities shows in general that the ring carbons are most significant, except in the N-(propyl)-1,8-naphthalimide,3′-phosphoric acid derivative, where charges and densities are localized in the phosphate group. Single point energy calculations, both in vacuum and solution were performed for each NI derivative. The adiabatic and vertical electron affinities and ionization potentials are given for each of the NI derivatives in the ground state. The results suggest that none of the five NI derivatives studied can oxidize DNA nucleobases via direct electron transfer from the ground states, and that the dark toxicity of the compounds is thus most likely very low.