Copper complexes coloured

The Colour Index (up to June 1991) Hsts 21 direct violets with disclosed chemical constitutions. Commercially important are Cl Direct Violet 9 [6227-14-1] (79) (Cl 27885) (sulfanihc acid coupled to cresidiue followed by alkaline coupling to V-phenyl J-acid) and Cl Direct Violet 66 [6798-03-4] (80) (Cl 29120) (a copper complex of 2-arniao-l-phenol-4-sulfonarnide (2 mol) coupled to 6,6 -imiQobis-l-naphthol-3-sulfonic acid). 

Simultaneous detenuination of Cu and Zn in the form of coloured PAR complexes is performed at pH 10 in the presence of pyrophosphate which binds the admixtures of Al, Fe and Mn into the inactive complexes. The measurements of the change in the optical density are made at 520 and 550 nm before and after the destmction of the complexes by EDTA, or at 530 nm before and after the destruction of the copper complexes by the thioglycolic acid and the destmction of the zinc complexes by EDTA. The detection limit for Cu is 2-5, for Zn - 3 p.g/diW. The application of these methodics at pH 8 enables one to determine simultaneously Cu and Zn at high excess of the latter. 

Place a drop of the acid test solution upon a spot plate, add 1 drop zinc acetate (1 %) solution and 1 drop of the reagent. The precipitated zinc tetra-thiocyanatomercurate(II) is coloured violet owing to the coprecipitation of the copper complex the composition of the precipitate is approximately Zn[Hg(SCN)4], Cu[Hg(SCN)4], The addition of copper ions to a precipitate of zinc tetrathiocyanatomercurate(II), already formed, has no effect. Sensitivity 01 pg Cu2+. Concentration limit 1 in 5 x 10s. 

Coloured copper complexes with EDTA and related reagents can be applied for determining Cu at higher concentrations. Cu has been determined as EDTA and NTA complexes by the derivative spectrophotometry [84,85]. Relatively high concentrations of Cu can be determined as the ammino complex (e = 120). Other sensitive methods are based on copper complexes with chloride (in water-acetone) and azide [86]. 

The oxidation of catecholamines like epinephrine has been widely used as source for superoxide dismutase assays. Upon oxidation the catecholamines are transformed to the coloured product adrenochrome. The rate of oxidation by superoxide is inhibited in the presence of superoxide dismutases Likewise the autoxidation of catecholamines at alkaline pH-values is diminished Intriguingly, low molecular mass copper complexes which display superoxide dismutase activity accelerate the autoxidation Therefore, the interaction between superoxide and catecholamines and its inhibition by SOD is thought not to be a simple chemical reactionRecently, this reaction was investigated in more detail Whilst adrenalin autoxidation is very specifically inhibited by SOD, the reaction with other catecholamines like noradrenalin or dihydroxyphenylalanine, having no free amino group, is much less specific. Only 20 % inhibition by CujZnjSuperoxide dismutase are observed. The autoxidation reaction itself is very complex (Scheme 2) and still not fully understood. 

Some phosphinodithioic salts are intensely coloured and have potential uses as analytical reagents. Copper complexes can be made by reacting sodium salts with a cupric halide (9.446). The copper compounds are colourless and diamagnetic and have a low solubility in organic solvents. Some octahedral tin complexes have important biocidal properties (9.447) (Figure 9.17). 

Helquist and his co-workers have now given more useful experimental details of the stereoselective synthesis of trisubstituted olefins by addition of alkyl-copper complexes, especially methylcopper, to acetylenes (Scheme 8). Clean results are obtained consistently only if the copper(i) bromide-dimethylsulphide complex (22) is white in appearance and its solutions are colourless. If either the solid or solution develops a pink colour (indicative of Cu" salts) then larger amounts of dienes formed from coupling of the alkenyl-copper intermediates (23), are obtained. Complex (22) is best stored under nitrogen, although manipu-... 

Phthalocyanine pigments. A limited colour range of blues and greens is available. The basic structure is an extremely chemically stable copper complex with outstanding heat, light and non migratory properties. 

In alkaline solution biuret, HN(CONH2)2 reacts with copper(II) sulfate to give a characteristic violet colour due to the formation of the complexes [Cu2(/l-OH)2(NHCONHCONH)4] (Fig. 28.6a) and [Cu(NHCONHCONH)2] . This is the basis of the biuret test in which an excess of NaOH solution is added to the unknown material together with a little CUSO4 soln a violet colour indicates the presence of a protein or other compound containing a peptide linkage. 

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