Macrocycles chelating

There is potential in the anti-HIV field. Polyoxometallates of the Keggin type bind to viral envelope sites on cell surfaces and interfere with virus adsorption. Metal-chelating macrocyclic bicyclam ligands are among the most potent inhibitors of HIV ever described, and there is considerable interest in the role of Zn proteins in the viral life cycle. 

Metal Type of ligand Ammine, Delocalized cyano, etc. chelate /macrocyclic it-Acid Type of study Photochemical Photophysical Mechanistic Theoretical... 

Martell, A. E., Hancock, R. D., Motekaitis, R. J., Factors affecting stabilities of chelate, macrocyclic and macrobicyclic... 

The peculiarities of classical localized coordination bonds (two-electron and two-center [1,4,5]) are displayed most clearly in MCC. Mostly, the elements of the first period of the Periodic Table (C, N, O) participate as electron donors in the formation of such bonds. In complexes of this type, the role of Ji-dative interactions is significant. These interactions are revealed in coordination compounds of ligands containing the elements of the next periods as donor centers (P, As, Sb S, Se, Te Cl, Br, I). We note that the examined complexes are the most successful objects to study the influence of ligand and metal nature on the character of the coordination bond, since, in this case, the factors which could distort this influence (chelate, macrocyclic, and other effects [117,135]) are absent. 

A general feature of MC is the presence of metallocycles in their molecules, whose main role is to produce stabilization effects (chelate, macrocyclic, and other effects) on the complexes [117,135-139]. An outstanding role in the study of this type of coordination compound belongs to the Russian scientist L.A. Chugaev (to whom the... 

The synthetic route described above corresponds to strategy I of Figure 2.22. Strategy II was in fact tested at first, since it involves well-controlled steps.54a 56 This approach requires the preliminary preparation of one single chelate macrocyclic component. However, once intermediate (F)... 

Figure 2.26. Assembly, by Cu(I)-templated threading, of two zinc porphyrins appended to a chelating macrocycle (67). Bis-chelate molecular threads 68, 69, and 70 provide threaded complexes 71, 72, and 73 respectively.

Thus, certain structural features, in particular incorporation of the central atom into a five-membered ring, chelate, macrocyclic and cryptate effects may stabilize the geometry of penta- and hexa-coordinate silicon species. Much of the insight as to which structural features might be expected to stabilize this species comes from studies of species involving higher valent states of other nonmetallic elements of the third row of the periodic table os-so )... 

Figure 32 Assembly, by copper(I)-templated threading, of a zinc(II) poq>hyrin (82) and a gold(III) porphyrin (89) appended to a chelating macrocycle. The bis-chelate molecular thread (85) affords complexes (90), (91), and (92) [123].

Figure 51 Principle of transition metal-templated synthesis of a [3]-rotaxane, from two chelating macrocycles (B) and a bis-chelate-containing molecular thread (A) functionalized with reactive end groups X (same conventions as in Figure 43). (ii) Threading step, affording prerotaxane (C) construction of the porphyrin stoppers providing copper(I)-complexed [3]-rotaxane (D).

In seeking to produce stable iron(O) complexes for the activation of arenes, a variety of interesting arsenic-sulfur heterocycles has been synthesized. Thus, with use of bis(3-chlofopropyl)phenylarsine (66) as the electrophile, the potentially chelating macrocycles (73)-(80) were prepared under high-dilution conditions in ethanol at 70°C from sulfide or various thiolates (Scheme 12) <81TL5035, 85CB2703>. The products were purified on alumina columns with use of benzene-diethyl ether as eluant. Except for crystalline (75), (77), and (78), the products were oils. 

Martell, A.E. Hancock, R.D. The chelate, macrocyclic, and cryptate effects. In Coordination Chemistry A Century of Progress Kaufman, G.B., Ed. American Chemical Society Washington, 1994, 241-254. 

Topology and the Chelate, Macrocycle and Cryptate Effects Increasing Topological Constraint... 

Figure 7. Topology and the chelate, macrocycle, and cryptate effects (Reproduced with permisison from reference 53. Copyright Battelle, 1993).

MARTEIX HANCOCK Chelate, Macrocyclic, and Cryptate Effects... 

The concepts described in this paper provide an understanding of the general principles governing the stabilities of metal complexes, chelates, macrocyclic complexes, and cryptate complexes. 

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