Compostos de coordenação de cobalto com ligantes redox ativos do tipo o-aminofenóis
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Data
2024-12-19
Autores
Bruzeguini, Carlos Eduardo Tartaglia
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Universidade Federal do Espírito Santo
Resumo
Redox-active ligands are a class of organic ligands that exhibit reduction and oxidation processes, presenting species with different charges and ambiguity in the oxidation state. When coordinated to metal centers, these ligands maintain these processes independent of the metal ion. The coordination compounds formed with this class of ligands exhibit electronic properties that cause them to exhibit redox and magnetic properties. Due to these characteristics, redox-active ligands are explored in catalysis applications and in the study of radical systems. They are important constituents for the formation of systems that exhibit valence tautomerism (VT) characteristics. This will exhibit electronic lability, that is, they have two quasi-degenerate electronic states, with close and accessible energy values. These states are interconverted with the help of external disturbances, such as temperature variation, incidence of light and pressure. The change between these states results in different optical and/or magnetic properties for the compound. This behavior is characteristic of the application of functional materials in molecular electronic devices, as it can specify a function for each property. The aim of this research was to evaluate whether o-aminophenol ligands can replace dioxolene ligands, which are the most used redox-active ligands in VT systems, to observe new compounds with the valence tautomerism phenomenon. For this purpose, the ligands H4L and H4dP, both o-aminophenols, were selected to form progression compounds with cobalt and iron metal centers. The products obtained had their structures determined by X-ray diffraction. From the analysis of the structures of the obtained compounds, it was concluded that the systems produced did not exhibit VT. In addition, the characteristics of the chosen ligands, conformational freedom and high reactivity, showed that they tend to form radical species in solution, promoting parallel reactions of intramolecular cycles and homolytic bond breaks. By studying the structures obtained, it is assessed that to form systems with VT using redox-active ligands of the aminophenol type, they must be those that preferentially coordinate in the iminosequinone species. For this, the ligand must have a tertiary amine or be an imine, unlike H4L and H4dP, which coordinated as aminophenolate
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Ligantes redox ativos , Compostos de coordenação , Tautomeria de valência , Redox-active ligands , Coordinated compound , Valence tautomerism