Effect And Mechanism Of Copper(â…¡) On Photolysis Of Imidazole Compounds

Under the solar irradiation, there were complex interactions between metals and organic compounds in combined pollution system, which can influence the photochemical behavior of the organic pollutants. Imidazole compounds had favorable biological activity and pharmacological effect, were used in Industry (curing agents, corrosion inhibitors), agriculture (herbicides), medicine (anticancer drugs, antihypertensive drugs) extensively. In present study, the complexation of copper-imidazole compounds were investigated. The effect of copper(Ⅱ) on photo degradation of imidazole compounds were also determined. Equation of quantitative was derived to analysis efficacy and mechanism of the interaction between copper(Ⅱ) and imidazole compounds in the photolysis process.Form of1:1copper-imidazole compounds complex was confirmed by ultraviolet spectrophotometry, the complex constants were:2.25×104L/mol (imazapyr),2.05×104L/mol (imazameth).3.24×104L/mol (imazethapyr). The structures of complex were characterized with the infrared spectroscopy, it showed the complexaction sites were the lactam nitrogen of imidazole and the pyridine nitrogen. Results of analog computation indicated that the structures of complex were stable five-membered ring. In the complex formation process, electrons transfered from imidazole compounds to copper(Ⅱ).Under simulated sunlight condition, copper(Ⅱ) can inhibit photogeradation of imidazole compounds, but had no influence on the photolysis pathway; The interactions between copper(Ⅱ) and excited state of imidazole compounds was proved by fluorescence spectroscopy and the addition of EDTA which act as a competitive ligand. The interaction can aslo inhibit as the complexation. The results of the quantitative equation showed photolysis rate of complex in the following order:imazapyr(1×10-5min-1)<imazameth(4×10-5min-1)<imazethapyr(2×10-5min-1), and the interaction constants of copper(Ⅱ) and Imidazole compounds were6.05×104L/mol(imazapyr),1.37×105L/mol(imazameth),1.28×103L/mol(imazethapyr); Effect of Ni, Mn, Mg, Ca, Cd, Co, Zn on photolysis of Imidazole compounds were also observed. Exciplex were formed with metals and excited state of Imidazole compounds. In this formation process electron transfered from imidazole compounds to metal ions. Complexation of metals can strengthen the stability of the structures of imidazole compounds, thus, inhibit the photolysis of imidazole compounds. Metals can also inhibit the photo degradation of imidazole compounds by the formation of exciplex with the excited state of imidazole compounds which have more efficacy than the complexation.