| Autor: |
Jörg Zimmermann, Werner Fudickar, Laurent Ruhlmann, Ulrich Siggel, Jürgen-Hinrich Fuhrhop |
| Rok vydání: |
2001 |
| Předmět: |
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| Zdroj: |
Journal of Electroanalytical Chemistry. 503:1-14 |
| ISSN: |
1572-6657 |
| DOI: |
10.1016/s0022-0728(00)00538-6 |
| Popis: |
Non-covalent cofacial heterodimers and -trimers between meso -tetraphenyl-octacarboxylate-porphyrin and β-tetracationic porphyrins have been prepared in bulk water. They are held together by Coulomb interactions between four or eight β-methylpyridinium and meso -phenylcarboxylate ion pairs. The observation of the UV–vis absorption titration indicated quantitative trimerization at concentrations >10 −6 M. The equilibrium constants in water were 2.3×10 6 M −1 for the dimerization and 1.7×10 7 M −1 for the conversion of the dimer to the trimer in water. Fluorescence of free base or zinc porphyrins was strongly diminished on heterodimerization and -trimerization by redox quenching. In the case of Mn(III) heterotrimer, electrochemistry and spectroelectrochemistry showed that all three Mn(III) ions were oxidized simultaneously to Mn(IV) at a potential close to 0.20 V versus Ag ∣ AgCl at pH 12. Electroreduction of the peripheral cationic Mn(III) porphyrins was achieved at −0.20 V versus Ag ∣ AgCl and gave the first multivalent trimers, namely Mn(II)P–Mn(III)P–Mn(II)P. The reduction of the central manganese porphyrin finally occurred at −0.60 V yielding Mn(II)P–Mn(II)P–Mn(II)P trimers. Heterotrimers Mn(III)P–H 2 P–Mn(III)P and H 2 P–Mn(III)P–H 2 P were also studied as reference compounds for electrochemical measurements. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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