Synthesis And Characterization Of Metal Complexes Of Azotic-heterocycle And Their Catalysis Study

Polyphenol oxidase (such as tyrosinase, catechol oxidase, and so on) and catalase are two important metal containing enzymes, which can catalytic oxidize phenolic compounds and are extensively used in the phenolic compounds removal in industry. Synthesizing new enzyme model complexes that mimic the structures of active sites of the enzymes is one of effective method to obtain new catalysts. In addition, we can also gain some insight on the mechanism of enzyme catalytic reaction from the study of model compounds.Two groups of model complexes were synthesized, one is benzimidazolyl containing metal compounds:[Mnâ…¡2(bbaa)2(H2O)2](ClO4)2 (1), [Mnâ…¡(bba)2](cba)(ClO4) (2) [Mnâ…¡(bba)(H2O)Cl2] (3), and copper complexes [Cuâ…¡(bbaa)(H2O)(NO3)] (4) and [Cuâ…¡(bba)Cl2] (5); the other group is Schiff base containing compounds:[Cuâ…¡(hppg)Cl](6), [Cuâ…¡2(hppg)2Cl2] (7), [Feâ…¢(hppg)Cl2](H2O)2 (8) and [Mnâ…¢(hppg)](Im)4(H2O)4(NO3)2 (9). In which, bbaa= N,N-bis(2-benzimidazolyl methyl)amino acetic acid, bba= bis(2-benzimidazolylmethyl) amine, cba= 2-chloro benzoic acid, hppg= N-(2-hydroxybenzyl)-N-(2-picolyl) glycine.Through comparing the structures of 1,3,4, and 5, and their relative catalytic activities with three phenolic compounds as substrates, and the effects of substrates, temperature, and oxidants on their oxidation activities, we found that complex 4 was most active in group one, it can oxidize phenol, catechol, and 2,6-dimethoxyphenol as well. Comparing to the copper complexes, manganese complexes are less active. The acitivity of manganese complexes were easy affected by the reaction conditions. In the second group, ferric complex 8 is most active and had higher affinity to 2,6-dimethoxyphenol. Based on the intermediates of the catalytic reactions with these compounds, the oxidation reaction mechanisms of these catalysts were discussed.