Four cobalt tetraphenylporphyrins which are substituted in the para-position of a phenyl ring were synthesized, and their abilities to accelerate peroxynitrite decomposition were studied in ethanol by UV-Vis spectrophotometer. The catalysis of peroxynitrite decomposition by cobalt porphyrins was firstly found, and the catalytic activities of cobalt porphyrins with electron-withdrawing groups located in the para-position of a phenyl ring were higher than those with electron-donating groups located in the para-position of a phenyl ring. The k_cat of TPPCoCl, T(p-CH₃)PPCoCl, T(p-OCH₃)PPCoCl and T(p-Cl)- PPCoCl are 1.69×10², 1.52×10², 1.43×10² and 1.20×10³ mol^－1•L•s^－1 respectively. T(p-R)PPCoCl catalyzed peroxynitrite decomposition through the formation of intermediates from the observation of kinetic traces and time-resolved UV-Vis spectrum.

Key words: cobalt porphyrin, catalytic activity, peroxynitrite, intermediate