Interfacial Hydrolysis in the μ-oxo Dimer Formation of Tetraphenylporphinatomanganese(III) in the Toluene/Water System

Abstract

The interfacial adsorption and dimerization behavior of tetraphenylporphinatomanganese(III)chroride (Mn(TPP)Cl) in the toluene/water two phase system was studied. The absorption spectra of the porphyrin complex in the organic phase were blue shifted with increasing of pH in the aqueous phase, suggesting the formation of the µ-oxo dimer. The interfacial species in these systems were examined by means of UV/vis external reflection (ER) spectrophotometry. ER spectral maxima were also blue shifted with the increase in pH, whereas the shape of the ER spectra in the basic conditions was different from that of the µ-oxo dimer. The observed results suggest that the hydroxide-coordinated monomer, Mn(TPP)OH, was generated from the Mn(TPP)(H2O) + at the interface under the basic conditions and that was further converted to the µ-oxo dimer, which was soluble into the toluene phase.

Aerobic oxidation of β-isophorone by tetraphenylporphyrin catalysts in pyridine solution

“…Given the relatively low solvent pH in these solutions, once H 2 O is formed in the course of the reaction, we deemed it unlikely that a -oxo dimer is formed. Formation of a -oxo dimer is known due to interaction of OH − under high pH conditions [51]. Thus, none of the above mentioned factors were considered in the computational models.…”