Spectroscopic and Kinetic Studies of Photochemical Reaction of Magnesium Tetraphenylporphyrin with Oxygen

Magnesium telraphenylporphyrin (MgTPP) was synthesized from meso-tetraphenylporphyrin (H2TPP) in N,N- dimethylformamide (DMF). The photochemical properties of M-TPP. in the presence of oxygen were investigated in dichloromethane (CHCl2) by conventional fluorescence, UV-vis, H-1 NMR, MALDI-TOF-MS, FTIR, and XPS spectroscopic techniques. Spectral analyses showed that under irradiation, MgTPP molecules reacted with O-2 molecules, and a stable 1:1 adduct was produced. During the photochemical reaction process, one oxygen molecule was bound to the pyrrolenine nitrogens in the MgTPP molecule, and the characteristic N-O bonds were identified using the FTIR and XPS techniques. The kinetics of the photochemical reaction of M-TPP with O-2 has been Studied in an oxygen-saturated solution. Under irradiation conditions, the experimental rate follows a pseudo-first-order reaction for MgTPR having a half-life from 40 to 130 min under various irradiation intensities. The kinetic rate constant of photochemical reaction of MgTPP with O-2 showed a linear dependence.