Relaxation Process of Photoexcited meso-Naphthylporphyrins while Interacting with DNA and Singlet Oxygen Generation.

Electron donor-connecting cationic porphyrins meso-(1-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (1-NapTMPyP) and meso-(2-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (2-NapTMPyP) were designed and synthesized. DFT calculations speculate that the photoexcited states of 1- and 2-NapTMPyPs can be deactivated via intramolecular electron transfer from the naphthyl moiety to the porphyrin moiety. However, the quenching effect through the intramolecular electron transfer is insufficient, possibly due to the orthogonal position of the electron donor and the porphyrin ring and the relatively small driving force: Gibbs energies are 0.11 and 0.07 eV for 1- and 2-NapTMPyPs, respectively. It was speculated that more than 0.3 eV of the driving force is required to realize effective electron transfer in similar electron-donor connecting porphyrin systems. These porphyrins aggregated around the DNA strand, accelerating the deactivation of their excited singlet state and decreasing their photosensitized singlet oxyge...