Macrocyclic complexes copper

Moi, M.K., Meares, C.F., McCall, M.J., Cole, W.C., and DeNardo, S.J. (1985) Copper chelates as probes of biological systems stable copper complexes with a macrocyclic bifunctional chelating agent. Anal. Biochem. 148, 249-253. 

In an extension of this study, the dissociation rates for the copper complexes of the corresponding 16- and 17-membered N5-macrocycles have been studied (Hay, Bembi, McLaren Moodie, 1984). Similar rate laws to that just given for the 15-membered ring complex also apply in these cases. It was found that there is an increase in rate as the ring size increases the respective kH constants being 0.049 dm6 mol-2 s 1 (15-membered), 4.85 dm6 mol 2 s 1 (16-membered) and 1.18 x 103 dm6... 

It has been recognized that sulfur donors aid the stabilization of Cu(i) in aqueous solution (Patterson Holm, 1975). In a substantial study, the Cu(ii)/Cu(i) potentials and self-exchange electron transfer rate constants have been investigated for a number of copper complexes of cyclic poly-thioether ligands (Rorabacher et al., 1983). In all cases, these macrocycles produced the expected stabilization of the Cu(i) ion in aqueous solution. For a range of macrocyclic S4-donor complexes of type... 

Subsequent reaction of porphyrazines 170 and 171 with Cu(OAc)2 resulted in the selective metalation within the macrocyclic cavity to provide the corresponding copper complexes 166 (62%) and 172 (47%). Treatment of pz 170 with manganese acetate and iron sulfate in dimethyl sulfate gave the dmso adducts 173 (70%) and 174 (85%), respectively (168). Axial ligation was also observed when other metals were incorporated such as cobalt acetate, nickel acetate, and zinc acetate to give the metal complexes 175 (83%), 176 (70%), and 177 (90%) as the hydrates. The axial ligand of... 

Copper(I) complexes can be generated by radical reduction of the corresponding Cu(II) complex. A few copper(I) macrocycles are remarkably stable but usually they are strong reducing agents reactive in O2, and disproportionate to copper(II) and metallic copper. 

A. Kandegedara, Ph.D. Dissertation, Electron-Transfer Kinetics of Copper Complexes with Macrocyclic Terdentate Ligands, Wayne State University, 2001. 

In this chapter, we would like to describe rotaxanes in which a new motion, pirouetting of the wheel around its axle, can be electrochemically triggered. The first distable copper-complexed rotaxanes 4(4)+ and 4(5)2 + synthesized in our group are represented in Fig. 14.7. The wheel of the rotaxane is a bis-coordinating macrocycle... 

The results obtained by cyclic voltammetry clearly show that upon oxidation or reduction of the central metal copper, the macrocycle is set in motion. Upon oxidation of 6(4)+, the resulting tetrahedrally coordinated Cu(II) is unstable as Cu(II) forms stable square planar complexes or higher coordination (five or six). Therefore, the macrocycle pirouettes around the axle permitting the restoration of a stable coordination, that is pentacoordination by the 2,2, 6 2"-terpyridine and 2, 2 -bipyridine... 

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... 

The value of log K for the copper complex of 6.24 is 4.3, whilst for that of 6.23 it is 1.97. The macrocyclic complex is thus about 100 times more stable than the open-chain complex, and this is presumably due to the macrocyclic effect. In this case, thermodynamic measurements have shown that Afor the macrocyclic and open-chain complexes are almost identical, and so the macrocyclic effect is due almost entirely to the entropy term. However, even with these ligands the involvement of solvation may not be neglected entirely. The stability values given above are for the complexes in aqueous solution if the measurements are repeated in 80 % aqueous methanol, the value of log K for the formation of the macrocyclic complex is only 3.5. A hole-size effect (section 6.6) is also apparent if we move to the larger thioether macrocycle 6.26. For the formation of the copper complex of 6.26 (again in 80 % aqueous methanol) log K is found to be 0.95. 

Let us start by considering the reaction of the copper(n) complex 6.49 with formaldehyde. Initially we might expect the diimine 6.50 to be formed, but this ignores the nature of the intermediates. As we saw earlier, the reaction of an amine with an aldehyde initially produces an aminol. Consider the addition of the second molecule of formaldehyde to 6.49. The product will be 6.51, which contains an imine and an aminol (Fig. 6-43). The imine is co-ordinated to a metal ion, and the polarisation effect is likely to increase the electrophilic character of the carbon. The hydroxy group of the aminol is nucleophilic and it is correctly oriented for an intramolecular attack upon the co-ordinated imine. The result is the formation of the copper(n) macrocyclic complex 6.52. 

Figure 6-44. The formation of a copper(n) macrocyclic complex from a three component reaction involving 6.49, formaldehyde and nitroethane. The product 6.54 arises from the reaction of one equivalent of 6.49 with two equivalents of formaldehyde and one of nitroethane.

When the copper complex of 7.62 reacts with ICH2(CH2OCH2)4CH2l in the presence of base, an intramolecular cyclisation occurs to form the macrocyclic ether 7.63. However, because of the arrangement of the starting ligands about the copper(i) centre, the two macrocycles are interlinked, and the consequence is the formation of the copper(i) complex of the catenand (catenand = catenane ligand) (Fig. 7-41). 

Agnus, Y., Louis, R., Weiss, R., Bimetallic copper(I) and copper(II) macrocyclic complexes as mimics for type-3 copper pairs in copper enzymes. J. Am. Chem. Soc. 1979, 101, 3381-3384. 

The examined compound behaves as an N,Te-donor ligand also in analogous cobalt and copper complexes [922]. The N,Te-ligand environment is very likely for complexes 530 [923], 531 [924], adduct 532 [925], and tellurium-containing macrocyclic Schiff bases 533 [926] ... 

Fig. 7.5 Phthalocyanine crystal structures a copper complex [12] (left) and the metal free macrocycle [13] (right)...

The use of metal ions as templates for macrocycle synthesis has an obvious relevance to the understanding of how biological molecules are formed in vivo. The early synthesis of phthalocyanins from phthalonitrile in the presence of metal salts (89) has been followed by the use of Cu(II) salts as templates in the synthesis of copper complexes of etioporphyrin-I (32), tetraethoxycarbonylporphyrin (26), etioporphyrin-II (78), and coproporphyrin-II (81). Metal ions have also been used as templates in the synthesis of corrins, e.g., nickel and cobalt ions in the synthesis of tetradehydrocorrin complexes (64) and nickel ions to hold the two halves of a corrin ring system while cycliza-tion was effected (51), and other biological molecules (67, 76, 77). 

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