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<p>Oxygen activation is one of the most challenging scientific issues confronting our universe. Chemistry plays a central role in solving this activation by developing molecular containers tailored to this application. In this study, six pyrazole-based ligands have been synthesized, characterized and investigated for their catalytic properties in the oxidation reactions of catechols to o-quinones and 2-aminophenol (OAP) to 2-aminophenoxazinone (APX). The synthesized ligands were characterized using Fourier-transform infrared spectroscopy (FTIR) measurements, UV–Vis spectroscopy, thermal analysis (Kofler bench and electrothermal capillary tube apparatus), thin-layer chromatography (TLC), nuclear magnetic resonance (<sup>1</sup>H NMR and <sup>13</sup>C NMR) analyses and mass spectrometry (MS). Their catalytic activities were evaluated through kinetic studies using different solvents, including tetrahydrofuran (THF) and acetonitrile (CH₃CN). The findings indicate that the in situ combination L<sub>6</sub>/Cu(CH<sub>3</sub>COO)<sub>2</sub> in THF exhibited the highest catecholase-like activity, with a catalytic rate of V = 5.596&#xa0;μmol.L⁻<sup>1</sup>&#xa0;min⁻<sup>1</sup>. Conversely, the L<sub>4</sub>/CoCl₂ complex in THF was the most effective catalyst for phenoxazinone synthase activity, achieving a reaction rate of V = 2.034&#xa0;μmol.L⁻<sup>1</sup>&#xa0;min⁻<sup>1</sup>. Notably, no catecholase activity was observed in acetonitrile. These results underscore the significant role of solvent choice in modulating catalytic efficiency. The present work expands upon these findings by incorporating a detailed kinetic study and analyzing solvent effects. The results are presented through comprehensive tables and figures, offering valuable insights into the catalytic mechanisms of these transition metal complexes. </p>

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Pyrazole-linked metal catalysts: driving oxidation of catechol and 2-aminophenol

  • 期刊论文

  • 发表日期：

    2025年5月9日

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  • Mohamed El Boutaybi,
  • Majda Chaabane,
  • Nadia Bouroumane,
  • Mohamed El Miz,
  • Mohamed Abou-Salama,
  • Rachid Touzani,
  • Zahra Bahari

摘要

Oxygen activation is one of the most challenging scientific issues confronting our universe. Chemistry plays a central role in solving this activation by developing molecular containers tailored to this application. In this study, six pyrazole-based ligands have been synthesized, characterized and investigated for their catalytic properties in the oxidation reactions of catechols to o-quinones and 2-aminophenol (OAP) to 2-aminophenoxazinone (APX). The synthesized ligands were characterized using Fourier-transform infrared spectroscopy (FTIR) measurements, UV–Vis spectroscopy, thermal analysis (Kofler bench and electrothermal capillary tube apparatus), thin-layer chromatography (TLC), nuclear magnetic resonance (1H NMR and 13C NMR) analyses and mass spectrometry (MS). Their catalytic activities were evaluated through kinetic studies using different solvents, including tetrahydrofuran (THF) and acetonitrile (CH₃CN). The findings indicate that the in situ combination L6/Cu(CH3COO)2 in THF exhibited the highest catecholase-like activity, with a catalytic rate of V = 5.596 μmol.L⁻1 min⁻1. Conversely, the L4/CoCl₂ complex in THF was the most effective catalyst for phenoxazinone synthase activity, achieving a reaction rate of V = 2.034 μmol.L⁻1 min⁻1. Notably, no catecholase activity was observed in acetonitrile. These results underscore the significant role of solvent choice in modulating catalytic efficiency. The present work expands upon these findings by incorporating a detailed kinetic study and analyzing solvent effects. The results are presented through comprehensive tables and figures, offering valuable insights into the catalytic mechanisms of these transition metal complexes.