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Cobalt triarylcorroles containing one, two or three nitro groups. Effect of NO₂ substitution on electrochemical properties and catalytic activity for reduction of molecular oxygen in acid media.

Abstract：

:Cobalt(III) triarylcorroles containing 0-3 nitro groups on the para-position of the three meso-phenyl rings of the macrocycle were synthesized and characterized by electrochemistry, mass spectrometry, (UV-vis) and (1)H NMR spectroscopy. The examined compounds are represented as (NO2Ph)(n)Ph(3-n)CorCo(PPh3), where n varies from 0 to 3 and Cor represents the core of the corrole. Each compound can undergo two metal-centered one-electron reductions leading to formation of Co(II) and Co(I) derivatives in CH2Cl2 or pyridine containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). A stepwise two electron reduction of each NO2Ph group of the compound is also observed. The first is reversible and occurs in a single overlapping step at the same potential which involves an overall one-, two- or three-electron transfer process for compounds 2-4, respectively. This indicates the lack of an interaction between these redox active sites on the corroles. The second reduction of the NO2Ph groups is irreversible and located at a potential which overlaps the Co(II)/Co(I) process of the compounds. Thin-layer UV-visible spectroelectrochemical measurements in CH2Cl2, 0.1 M TBAP demonstrate the occurrence of an equilibrium between a Co(III) π-anion radical and a Co(II) derivative with an uncharged macrocycle after the first controlled potential reduction of the nitro-substituted corroles. All four cobalt corroles were also examined as catalysts for the electroreduction of O2 when coated on an edge-plane pyrrolytic graphite electrode in 1.0 M HClO4. This study indicates that the larger the number of nitro-substituents on the cobalt corrole, the better the compound acts as a catalyst.

journal_name

J Inorg Biochem

journal_title

Journal of inorganic biochemistry

authors

Li B,Ou Z,Meng D,Tang J,Fang Y,Liu R,Kadish KM

doi

10.1016/j.jinorgbio.2013.12.014

subject

Has Abstract

pub_date

2014-07-01 00:00:00

pages

130-9

eissn

0162-0134

issn

1873-3344

pii

S0162-0134(14)00004-X

journal_volume

136

pub_type

杂志文章

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Cobalt triarylcorroles containing one, two or three nitro groups. Effect of NO₂ substitution on electrochemical properties and catalytic activity for reduction of molecular oxygen in acid media.