Spectrophotometric and electrochemical investigations of (tetrakis(1-methylpyridinium-4-yl)porphine)iron(III) ion in aqueous solution.
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The equilibria among the species of [tetrakis(1-methylpyridinium-4-yl)porphine]iron(III) ion (Fe(III)–TMPyP) in aqueous solution and the redox reactions of their central metals were investigated by means of spectrophotometric, electrochemical and spectroelectrochemical methods. Two acid-dissociation equilibria involving three monomeric species of Fe(III)–TMPyP were found: one with a p<I>K</I><SUB>a</SUB> of 5.5 and the other with a p<I>K</I><SUB>a</SUB> of <I>ca.</I> 12. After electrochemical reduction, an equilibrium between two monomeric species of Fe(II)–TMPyP with a p<I>K</I><SUB>a</SUB> of 11 was observed. In the Fe(III)–TMPyP solution at relatively high concentration, two additional different species, probably dimeric, were found in the pH regions of 5–8 and 9–13, respectively. The consistency of specification of the species with the scheme of redox reactions is discussed.
- Bulletin of the Chemical Society of Japan
Bulletin of the Chemical Society of Japan 55(11), 3515-3519, 1982
The Chemical Society of Japan