The electrochemistry of water‐soluble manganese porphyrins (Mn(4‐TMPyP)) has been studied as an electrochemically‐active film on double‐stranded deoxyribonucleic acid (dsDNA) modified electrodes in solutions at various pH. An electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ deposition of DNA on gold disk electrodes, and Mn(4‐TMPyP) (manganese meso‐tetrakis‐(N‐methyl‐4‐pyridyl)porphyrin) deposition on DNA film modified electrodes. MnII(4‐TMPyP) (the reduced form) is more easily deposited on a DNA film than MnIII(4‐TMPyP) (the oxidized form). Electrodeposition of Mn(4‐TMPyP) can be performed in strong basic aqueous solutions, and shows two redox couples with electrochemically active voltammograms. The films can also be produced on glassy carbon, platinum, gold, and transparent semiconductor tin (IV) oxide electrodes. The Mn(4‐TMPyP)/DNA film was electrocatalytically oxidative for hydrazine, hydroxylamine, and SO in a basic aqueous solution through a Mn(IV) species. The electrocatalytic efficiency of MnIV(O)(4‐TMPyP) was observed to be greater than (OH)MnIV(O)(4‐TMPyP). Electrocatalytic oxidation by a Mn(4‐TMPyP) film as a catalyst for hydrazine oxidation is also discussed. This shows a new anodic peak current in the second segment after the positive scan during electrocatalytic oxidation, and is pH dependent. 相似文献
Herein, we report the synthesis of sulfur-substituted boron(III) subphthalocyanines (SubPcs) with cationic axial ligands. Subphthalocyanines were synthesized by a condensation reaction using the corresponding phthalonitriles and boron trichloride as a template. An aminoalkyl group was introduced on the central boron atom; this process was followed by N-methylation to introduce a cationic axial ligand. The peripheral sulfur groups shifted the Q band of SubPcs to a longer wavelength. The cationic axial ligands increased the polarity and enhanced the hydrophilicity of SubPcs. The effect of axial ligands on absorption and fluorescence properties is generally small. However, a further red shift was observed by introducing cationic axial ligands into the sulfur-substituted SubPcs. This change is similar to that in sulfur-substituted silicon(IV) phthalocyanines. The unique effect of the cationic axial ligand was extensively investigated by theoretical calculations and electrochemistry. In particular, the precise oxidation potential was determined using ionization potential measurements. Thus, the results of the present study provide a novel strategy for developing functional dyes and pigments based on SubPcs. 相似文献
The DNA cleavage properties of two cationic manganese porphyrins possessing different peripheral substituents were compared. The identical nature of the strand scission patterns of the porphyrins on a 139 base pair restriction fragment of pBR-322 DNA, along with other evidence, suggests that the porphyrin is end-on bound via the minor groove in a melted or partially melted region of DNA. This unusual binding mode underscores the potential of outisde binding cationic metalloporphyrins as probes for low melting regions of DNA 相似文献
The factors that affect acceleration and high trans/cis selectivity in the catalytic cyclopropanation reaction of styrene with ethyl diazoacetate by cobalt N-confused porphyrin (NCP) complexes were investigated using density functional theory calculations. The reaction rate was primarily related to the energy gap between the cobalt–carbene adduct intermediates, A and B, which was affected by the NCP skeletons and axial pyridine ligands more than the corresponding porphyrin complex. In addition, high trans/cis stereoselectivity was determined at the TS1 and, in part, in the isomerization process at the carbon-centered radical intermediates, Ctrans and Ccis. 相似文献
The oxygen reduction reaction (ORR) is essential in many life processes and energy conversion systems. It is desirable to design transition metal molecular catalysts inspired by enzymatic oxygen activation/reduction processes as an alternative to noble-metal-Pt-based ORR electrocatalysts, especially in view point of fuel cell commercialization. We have fabricated bio-inspired molecular catalysts electrografted onto multiwalled carbon nanotubes (MWCNTs) in which 5,10,15,20-tetra(pentafluorophenyl) iron porphyrin (iron porphyrin FeF20TPP) is coordinated with covalently electrografted axial ligands varying from thiophene to imidazole on the MWCNTs’ surface. The catalysts’ electrocatalytic activity varied with the axial coordination environment (i. e., S-thiophene, N-imidazole, and O-carboxylate); the imidazole-coordinated catalyst MWCNTs-Im-FeF20TPP exhibited the highest ORR activity among the prepared catalysts. When MWCNT-Im-FeF20TPP was loaded onto the cathode of a zinc−air battery, an open-cell voltage (OCV) of 1.35 V and a maximum power density (Pmax) of 110 mW cm−2 were achieved; this was higher than those of MWCNTs-Thi-FeF20TPP (OCV=1.30 V, Pmax=100 mW cm−2) and MWCNTs-Ox-FeF20TPP (OCV=1.28 V, Pmax=86 mW cm−2) and comparable with a commercial Pt/C catalyst (OCV=1.45 V, Pmax=120 mW cm−2) under similar experimental conditions. This study provides a time-saving method to prepare covalently immobilized molecular electrocatalysts on carbon-based materials with structure–performance correlation that is also applicable to the design of other electrografted catalysts for energy conversion. 相似文献
Slow electron transfer to manganese(iii) porphyrins results when the macrocycle deviates from planarity. This was demonstrated by measuring the kinetics of homogeneous electron transfer from a series of semiquinone radical anions to synthetic manganese porphyrins (shown schematically; R1=H, Cl, F; R2=H, F). Three of the four porphyrins studied have nonplanar macrocycles. These results could have implications for the role of manganese in biological electron transfer processes. 相似文献
The dark side of the Mn : A manganese(III) complex bearing a 13‐membered macrocyclic ligand ( 1 , see picture) binds a peroxo ligand in a side‐on η2 fashion. The reactivity of 1 is influenced by the introduction of anionic ligands trans to the peroxo group. Electronic and structural changes upon trans‐ligand binding explain the increased nucleophilicity of the resulting complexes 1 ‐X.
