Influence of the Type of Macrocycle on the Stabilisation of the High Oxidation State of the Manganese Ion and Electrode Processes
Dinuclear di-<i>µ</i>-oxo complexes of Mn<sup>3+</sup> and Mn<sup>4+</sup> ions, and mononuclear complexes of Mn<sup>3+</sup> ions with tetraazamacrocycles ([12]aneN<sub>4</sub>, [14]aneN<sub>4</sub>, [15]aneN<sub>4</su...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-04-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/8/1860 |
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| Summary: | Dinuclear di-<i>µ</i>-oxo complexes of Mn<sup>3+</sup> and Mn<sup>4+</sup> ions, and mononuclear complexes of Mn<sup>3+</sup> ions with tetraazamacrocycles ([12]aneN<sub>4</sub>, [14]aneN<sub>4</sub>, [15]aneN<sub>4</sub>) and <i>C</i>-substituted derivative (Me<sub>6</sub>[14]aneN<sub>4</sub>) as well as mononuclear complexes of Mn<sup>2+</sup> ions with <i>N</i>-substituted derivatives ((<i>N</i>-Me)<sub>2</sub>[14]aneN<sub>4</sub>, (<i>N</i>-Me)<sub>4</sub>[14]aneN<sub>4</sub>, (<i>N</i>-Me)Me<sub>2</sub>py [14]aneN<sub>4</sub>) and with oxo<sub>2</sub>[14]aneN<sub>4</sub> were studied. Based on spectroscopic (UV VIS and IR) and conductometric studies, the types of synthesised complexes (<i>cis</i> or <i>trans</i> isomers of mononuclear Mn<sup>3+</sup> complexes, oxygen bridges and class II according to Robin and Day classification for dinuclear complexes) were determined. On the basis of voltammetric and spectroelectrochemical studies, <i>trans-cis</i> isomerisation at the level of Mn<sup>2+</sup> ion complexes and <i>cis-trans</i> isomerisation at the level of Mn<sup>3+</sup> ion complexes were demonstrated for complexes of ligands with free C positions. The <i>N</i>-substituted derivatives oxidise according to the EC mechanism, in which the follow-up reaction is a disproportionation reaction. The thermodynamic stabilisation of Mn<sup>3+</sup> ions was determined by comparing the formal potentials (<i>E<sub>f</sub></i><sup>0</sup>), the disproportionation constants (<i>k</i><sub>1</sub>) and the formation constants (<i>β<sup>III</sup></i>). The study showed the possibility of oxidation of mononuclear, pseudo-octahedral Mn<sup>3+</sup> ion complexes to dinuclear complexes and the greatest stabilisation of Mn<sup>3+</sup> ions, both in monomers and dimers of ligands with free <i>N</i> positions. |
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| ISSN: | 1420-3049 |