2-Methylimidazole Copper Iminodiacetates for the Adsorption of Oxygen and Catalytic Oxidation of Cyclohexane

Abstract

The mixed-ligand copper(II) iminodiacetates [Cu(ida)(2-mim)(H2O)2]·H2O (1), [Cu(ida)(2-mim)2]·2H2O (2), [Cu(ida)(2-mim)(H2O)]n·4.5nH2O (3), and [Cu2(ida)2(2-mim)2]n·nH2O (4) (H2ida = iminodiacetic acid, 2-mim = 2-methylimidazole) were obtained from neutral or alkaline solutions at different temperatures. The novel complex 4 contains very small holes with diameters of 2.9 Å, which can adsorb O2 selectively and reversibly between 1.89 to 29.90 bars, compared with the different gases of N2, H2, CO2, and CH4. This complex is stable up to 150 °C based on thermal analyses and XRD patterns. The four complexes show catalytic activities that facilitate the conversion of cyclohexane to cyclohexanol and cyclohexanone with hydrogen peroxide in a solution. The total conversion is 31% for 4.

Keywords

• copper
• iminodiacetic acid
• 2-methylimidazole
• catalytic oxidation of cyclohexane
• gas adsorption