Protolytic behavior of axially coordinated hydroxy groups of Tin(IV) porphyrins as promising molecular catalysts for water oxidation
| Autor: | Siby Mathew, Yutaka Ohsaki, Daisuke Yamamoto, Sebastian Nybin Remello, Fazalurhaman Kuttassery, Haruo Inoue, Hiroshi Tachibana, Yu Nabetani, Arun Thomas |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Chemistry
General Chemical Engineering Inorganic chemistry General Physics and Astronomy chemistry.chemical_element 02 engineering and technology General Chemistry Pourbaix diagram 010402 general chemistry 021001 nanoscience & nanotechnology Electrochemistry 01 natural sciences Medicinal chemistry 0104 chemical sciences Catalysis Artificial photosynthesis chemistry.chemical_compound Deprotonation Cyclic voltammetry 0210 nano-technology Hydrogen peroxide Tin |
| Zdroj: | Journal of Photochemistry and Photobiology A: Chemistry. 358:402-410 |
| ISSN: | 1010-6030 |
| DOI: | 10.1016/j.jphotochem.2017.09.053 |
| Popis: | A series of four Tin(IV)porphyrins with different substituents on meso-phenyl groups, trans-dihydroxy-5,10,15,20-tetra(p-tolyl)porphyrinatetin(IV) (Sn(IV)TTP(OH)2), trans-dihydroxy-tetra(2,4,6-trimethyl)phenylporphyrinatetin(IV) (Sn(IV)TMP(OH)2), trans-dihydroxy-5,10,15,20-tetra(p-carboxyphenyl)porphyrinatetin(IV) (Sn(IV)TCPP), and trans-dihydroxy-5,10,15,20-tetra(N-methyl-4′-pyridiniumyl)porphyrinatetin(IV) (Sn(IV)TMPyP(OH)2) have been prepared and characterized focusing on their protolytic behavior of the axial ligands, hydroxy groups, both in the ground and excites states as well as their electrochemical oxidation behavior. The two axially ligating hydroxy groups on each Tin(IV)-porphyrins exhibit protonations and deprotpnations in five steps. The pKa value of each protolytic equilibrium in the ground states was spectrophotometrically determined, while fluorescence decay time profiles indicate that the protolytic processes are sufficiently slower than the intrinsic fluorescence decay rates to lead to non-protolysis in the excited states. The oxidation peak potentials were determined by cyclic voltammetric analysis. Pourbaix diagram of each protolytic species of Sn(IV)TMPyP in water indicated that the one-electron oxidation of fully deprotonated Sn(IV)TMPyP(O−)2 is not a proton-coupled process, while the doubly hydroxy coordinated species Sn(IV)TMPyP(OH)2 has a proton-coupled one. Tin(IV)-porphyrins exhibit efficient catalytic currents on the first oxidation wave in their cyclic voltammetry and the saturated catalytic currents were high enough in a wide range of pH to be promising as water oxidation catalysts. This is the first detailed study on Tin(IV)-porphyrins to examine water oxidation ability of the one-electron oxidized form against twenty kinds of species (five protolytic species for each of the four Tin(IV)-porphyrins). |
| Databáze: | OpenAIRE |
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