Ternary Complexes of Copper II

Battaglia, L. P, Corradi, A. B., Menabue, L., Pellacani, G. C., Prompolini, P. and Saladani, M. (1982). Ternary complexes of copper(II) with A-protected amino acids and A -methlyimidazole. Crystal and molecular structures of bis(A-acetyl-a-alaninato)bis(M-methlyimidazole)copper(II) dihydrate. J. Chem. Soc, Dalton Trans., 781. 

There has been considerable interest in the chemistry of ternary complexes of copper(II) containing a bidentate aromatic nitrogen base such as 1,10-phen-anthroline (phen) or 2,2,-bipyridine (bpy) and a bidentate oxygen donor ligand or an amino acid,1 6 as some of these could possibly serve as models for enzyme-metal ion-substrate complexes. Two procedures are described below for the convenient, high-yield preparation of two such complexes. 

Dimeric copper caprate is responsible for the ability of capric acid to extract copper(ii) in organic solvents. Ternary complexes of copper(i) with bipy and cycloalkane-1,1-dicarboxylic acids, Cu(A)(B), are blue and contain NjOj co-ordination. Copper(ii)-edta complex solutions have much higher intensities in v(M—O) and v(M—N) than those of other metals. ... 

Patel, R.N., Gokhale, P, and Pandeya, K.B. (1999) Ternary complexes of copper-, nickel-, and zinc(II) with some peptides and imidazoles, A potentiometric study. J. Indian Ghent. Soc, 76, 475 -479. 

The effect of chloride ion was interpreted in terms of the formation of various ternary complexes between Cu(II)-ascorbate and Cl-. It was demonstrated that the involvement of copper(I) is feasible and a corresponding mechanism was presented as an alternative to the Cu(II)/ Cu(III) model. 

Patra AK, Dhar S, Nethaji M, Chakravarty AR. Visible light-induced nuclease activity of a ternary mono-phenanthroline copper(II) complex containing L-methionine as a photosensitizer. Chem Commun 2003 1562-3. 

Type IV includes chiral phases that usually interact with the enantiomeric analytes through the formation of metal complexes. There are usually used to separate amino acid enantiomers. These types of phases are also called ligand exchange phases. The transient diastereomeric complexes are ternary metal complexes between a transitional metal (usually Cu +), an amino acid enantiomeric analyte, and another compound immobilized on the CSP which is able to undergo complexation with the transitional metal (see also the ligand exchange section. Section 22.5). The two enantiomers are separated based on the difference in the stability constant of the two diastereomeric species. The mobile phases used to separate such enantiomeric analytes are usually aqueous solutions of copper (II) salts such as copper sulfate or copper acetate. To modulate the retention, several parameters—such as the pH of the mobile phase, the concentration of the copper ion, or the addition of an organic modifier such as acetonitrile or methanol in the mobile phase—can be varied. 

TABLE III. Stability Constants of Copper(II) Ternary Complexes of CDmh... 

TABLE rv. Stability Constants for the Formation of Copper(II) Ternary Complexes of CDampy with L/D-alanine or -tryptophan at 25°C and I = 0.1 mol dm (KNO3). 

Figure 7. Schematic of copper(II) ternary complexes of CDampy on the right [Cu(CDampy)(L-TrpO), on the l t [Cu(CDampy)(D-TrpO)] ...

The analysis of the c.d. spectra of copper(II) mixed complexes supports the previously hypothesis put forward for chiral recognition. In fact, whilst the spectra of aliphatic amino acid pairs are all virtually superimposible, for the mixed complexes of aromatic amino acids the c.d. spectra are remarkably different for each diastereomeric pair in both the UV and the visible region, as shown in Figure 8 for the TrpO in the copper(II) ternary complexes with CDhm [35]. 

In order to obtain independent evidence for the involvement of the cyclodextrin cavity, fluorescence measurements were carried out for copper(II) ternary complexes with L- or D-tryptophan. In fact, the fluorescence spectrum of tryptophan has already been shown to be sensitive to the polarity of the microenvironment in which it is located and has been used in many studies as a probe for the conformation of proteins and peptides [53]. As for many fluorophores, the indole fluorescence of Trp is quenched by the copper(II) ion this effect has been used as a measure of the stability constants of copper(II) complexes [54, 55]. In a recent work, it has been shown that the fluorescence of dansyl derivatives of amino acids undergo enantioselective fluorescence quenching by chiral copper(n) complexes and that fluorescence measurements can be used for the study of enatioselectivity in the formation of ternary complexes in solution [56]. Bearing this in mind, we performed the same type of experiments by adding increasing amounts of the [Cu(CDhm)] + complex to a solution of D- or L-tryptophan [36]. The fluorescence titration curve shows that the artificial receptor inhibits the indole... 

Patra AK, Dhar S, Nethaji M, Chakravaity AR (2005) Metal-assisted red light-induced DNA cleavage by ternary L-methionine copper(II) complexes of planar heterocyclic bases. Dalton Trans 896-902. doi 10.1039/B416711B... 

Sigel and co-workers" investigated the interaction between the aromatic rings of phenyl carboxylates (Ph-(CFl2)n-C02) and 1,10-phenanthroline in ternary copper(II) complexes. Variation of the number of methylene units between the aromatic ring and the carboxylate group (n=0-5) revealed that the arene - arene interaction is most pronounced for n=l. This interaction is more efficient in a 60% 1,4-... 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

In non-aqueous solution, the copper catalyzed autoxidation of catechol was interpreted in terms of a Cu(I)/Cu(II) redox cycle (34). It was assumed that the formation of a dinuclear copper(II)-catecholate intermediate is followed by an intramolecular two-electron step. The product Cu(I) is quickly reoxidized by dioxygen to Cu(II). A somewhat different model postulated the reversible formation of a substrate-catalyst-dioxy-gen ternary complex for the Mn(II) and Co(II) catalyzed autoxidations in protic media (35). 

In analogy to the carboxylate binding by zinc-containing cyclodextrin 10 (see Sect. 2), Lewis acidic centers such as a copper(II) histamine unit may also serve for the chelation of the (deprotonated) 2-aminoacetate substructure of a-amino acids [51], Rizzarelli, Marchelli et al. used a respective j8-cyclodextrin derivative for the formation of the ternary complexes 36 and 37 with racemic... 

Enantioselective metal chelation is a technique that has been applied to the separation of amino acid enantiomers. In the method, a transition metal-amino acid complex, such as copper(II)-aspartame, in which the full coordination of the complex has not been reached, is added to the buffer. The amino acid enantiomers are able to form ternary diastereomeric complexes with the metal-amino acid additive if there are differences in stability between the two complexes, enantioselective recognition can be achieved. 

The aldehyde or ketone can now desorb, leading to the initial copper(I) hydrazide complex 13 which re-enters the catalytic cycle. The replacement of DEAD-H2 12 by DEAD 19 can be easily understood when considering this catalytic cycle. Indeed, several entries to the main catalytic cycle are possible, either via the hydrazino copper species 13 or via the direct formation of the ternary loaded complex 18 from the azo-derivative 19, Phen CuCl 3 and the alcohol 1. The key-role played by the hydrazine or azo compounds can also be readily appreciated when considering the proposed mechanistic rationale. The hydrazide, not only helps in reducing the copper(II) salt to the copper(I) state but, by virtue of its easy passage into the azo derivative, it also acts as a hydrogen acceptor, allowing the efficient oxidation of the alcohol into the carbonyl compound. 

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