EFFECTS OF AXIAL LIGANDS ON THE ELECTRON-TRANSFER CATALYZED BY MANGANESE TETRAKIS(PENTAFLUOROPHENYL)PORPHYRIN IN POLY(GAMMA-METHYL L-GLUTAMATE) MEMBRANE

Poly(gamma-methyl L-glutamate) (PMLG) membrane containing manganese tetrakis(pentafluorophenyl)porphyrin(a)) (MnPFPP) has been studied for the transmembrane redox reaction between dithionite and ferricyanide in separated solutions. The effects of the ligand species, namely, OH-, Cl-, imidazole (1m), pyrazine (Pyz), triethylamine (TEA), and pyridine (Py), on the electron transfer rate in the membrane were examined. UV/VIS spectroscopy and sorption measurements confirm that these ligands are sorbed by the membrane from the external buffer, solution and coordinate to MnPFPP. With the membrane containing 160 mumol . g-1 of MnPFPP, the apparent rate factor, estimated as the pseudo-first-order rate constant of the bleach of ferricyanide times membrane thickness, follows the order Im much greater than Cl- > Pyz > TEA, OH-, Py almost-equal-to 0, suggesting that Im, Cl- and Pyz are effective ligands for the electron transfer. Such a ligand-specific transfer stems from the electron-transferability of the ligands between MnPFPP's.