Transmembrane Electron Transfer Catalyzed by Porphyrin Derivtives

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1) Poly (ethylene glycol) [PEG] -linked porphyrin derivatives separated by spacer methylene groups (Cn), PEG-Cn-MPFPP (M = H_2, Mn ; n = 0,5,11), PEG-C_<11>-MTTP (M = H_2, Mn), and PEG-C_0-MPFPPBr_8 (M = H_2, Mn) (Scheme 1) were synthesized. The porphyrin portion of poly (ethylene glycol) [PEG] -linked fluorinated porphyrin derivative has been anchored onto a lipid bilayr. PEG-linked fluorinated porphyrins associated easily with phospholipid bilayrs and are chemically stable against oxidant such as H_2O_2. An efficient energy transfer from phospholipid-linked zinc porphyrin, PE-C_0-ZnPFPP (Scheme 1) to externally added PEG-Cn-H_2PFPP (n = 0,5,11) in the lipid bilayr was observed, depending on the length of Cn and the porphyrin structure.Ground state transmembrance electron transfer catalyzed by PEG-Cn-MnPFPP (n = 0,5,11) and PEG-C_<11>-MnTTP revealed that the porphyrin causes a significant accelerated electron transfer especially when n = 11. Comparison of PEG-C_<11>-MnPFPP- and PEG-C_ … More <11>-MnTTP-catalyzed electron transfer is discussed. The electron transfer rate was controlled not only by the separated spacer methylene groups between the porphyrin and PEG moieties but also by the structures of porphyrins.2) Zinc hybrid porpyrin dimer (ZnTTP-C2-H2PFPP,ZnTTP-C2-H2TTP,ZnPFPP-C2-H2PFPP and ZnPFPP-C2-H2TTP) and manganese halogenated porphyrin dimers (MnPFPP-C2-MnPFPP,MnPFPP-C2-MnDCPP,and MnDCPP-C2-MnDCPP) covalently bridged by a dimethylene moiety (Scheme 1) were synthesized and characterized by UV-vis spectra, fluoresecence spectra and cyclic voltammograms. These porphyrin dimers could be embedded into the lipid bilayrs of liposomal membrance. The redox potential of halogenated porphyrin dimers increased with increasing of halogen portions on the porphyrin rings. An efficient energy transfer of the excited singlet state in the covalently-linked zinc hybrid dimers from zinc porphyrin to a free base porphyrin was observed, depending on the porphyrin structure. The manganese halogenated porphyrin dimers showed catalytic activities of transmembrance electron transfer and the hydroxylation of toluene by H2O2, in which these catalytic activities depend on the steric effect of halogen portions on the porphyrin ring and also the presence of imidazole.3) Transmembrane electron transfer across S-cyanoethylated keration (SCEK) and liposomal membranes catalyzed by (1), MnTTP- (CH2) n-MnP (COOMe) 3, n=2,3,12 showed that an enhanced electron transfer wasobserved especially when n=2or3 on (1) in these membranes and imidazole was present. Furthermore, enhanced electron transfer between porphyrins in membranes cast on a glassy carbon electrode was observed especially in hydrophilic keratin membranes containing manganese protoporphyrin dimethyl esters (MnPPDME). An imidazole derivative playd an important role on the electron transfer in hydrophobic S-cyanoethylated keratin membranes containing MnPPDME. Less