Copper complexes imidazole

The mixture is then chilled in an ice bath for at least 3 hours, and the olive-brown precipitate of the sparingly soluble copper complex of imidazole derivatives is filtered. The product is washed with about 500 ml. of cold water, suspended while moist (Note 4) in 11. of water, and rendered just acid to litmus by the addition of concentrated hydrochloric acid (about 40 ml.). Hydrogen sulfide is then passed into the suspension, with frequent shaking, until precipitation of the copper is complete (2-3 hours). The precipitate is filtered and extracted with 500 ml. of hot water in two or three portions. The clear, light brown to reddish brown filtrate and washings are boiled for 15 minutes, and then 60 g. (0.26 mole) of picric acid is added with stirring heating is continued until solution is complete. 

V to IX), the copper complexes of the imidazoles also precipitated from the reaction mixture, and were filtered off. Oxalic acid and 4(5)-imidazole (30) were determined in the filtrate.11 40,41 The complex was suspended in hot water,11,29 32-40,41,43 47 50 53,88 dilute sulfuric acid,48,49 or dilute hydrochloric acid,44 the copper was removed as the sulfide, with hydrogen sulfide or sodium sulfide,49 and the excess of hydrogen sulfide was removed with lead acetate.11 40 41,50 The clear... 

The reaction of imidazole-4,5-dicarbaldehyde with 2-aminoethylpyridine in the presence of copper(II) chloride has enabled the preparation of a binuclear complex (equation 2).29 A more common class of binuclear complex is based on template reactions of a phenolic dialdehyde with various amines and includes the copper complexes (14)30 31 and (15).32 Reactions of this type can be extended to the synthesis of macrocyclic binuclear complexes such as (16).33,34... 

Zinc and other metal ions have been found to promote pyrrole hydrogen ionization in 2-(2 -pyridyl)imidazole.269 Complexation studies114 on the systems N-methyl-histamine and NN-dimethylhistamine with bivalent zinc, copper, cobalt, and nickel have shown that the stabilities of the complexes follow the Irving-Williams series. With respect to the variation of a ligand with the same metal ion, the stability decreases in the series histamine, N-methylhistamine, NN-dimethylhistamine, possibly as a result of steric hindrance. The complexes are assigned the structure (12). 

The structure and enzyme kinetics of bovine erythrocyte superoxide dismutase are reviewed. The protein has a novel imidazolate-bridged copper(II)-zinc(II) catalytic center in each of two identical subunits. Since a C /Cu1 redox couple is responsible for the dismutase activity of the enzyme, the role of zinc is of interest. Both 220-MHz NMR measurements of the exchangeable histidine protons and chemical modifications using diethylpyrocarbonate demonstrate that zinc alone can fold the protein chain in the region of the active site into a conformation resembling that of the native enzyme. Other possible roles for zinc are discussed. Synthetic, magnetic, and structural studies of soluble, imidazolate-bridged copper complexes of relevance to the 4 Cu(II) form of the enzyme have been made. 

Figure 11. Diagrammatic representation of active site which includes a four-coordinate copper complex, sugar-substrate bound outer-sphere to the Cu(II) atom, imidazole and indole rings, and nonpolar side chains (X). The distance between the Cu(II) and indole is estimated by fluorescence energy-...

Imidazole copper(II) complexes had previously functioned as catalysts in the oxidative coupling polymerization of DMP [183-186]. The mechanism which was proposed for this reaction involved the participa-... 

Initially, copper(II) coordinates to the octapeptide angiotensin II (Asp Arg Val Tyr Ile-His-Pro-Phe) at the imidazole nitrogen. At neutral pH the main copper complex is CuL, which is a 3N complex (Figme 2). The copper(II) is bonded via the imidazole nitrogen of the histidine residue, and two deprotonated peptide nitrogens. As the pH is raised above 8.0, the coordination site changes to the N-terminus... 

Figure 3 Binuclear copper complexes in octopus hemocyanin (a) and sweet potato catechol oxidase (b) showing the thioether linkage between a cysteine residue and a directly coordinating histidine imidazole. Heteroatoms (N,0,S) are indicated by a shaded quadrant. [ortep-III views based on PDB ID 1JS8 and IBTl]...

Wilkins BJ, Moore DE. Photolytic rearrangement of metronidazole to 1-hydroxyethyl-4-hydroxyimino-5-oxo-imidazole and the formation of copper complexes of these compounds. Photochem Photobiol 1988 47 481 84. 

Collman, J. P., Zhong, M. An Efficient Diamine-Copper Complex-Catalyzed Coupling of Arylboronic Acids with Imidazoles. Org. Lett. 2000, 2,1233-1236. 

Electron transfer by copper complexes with imidazole and polypyridines 04CRV651. 

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