Receptors macrobicyclic

Figure 12. Multiple-varied receptors macrobicycle with sites for metal ion and substrate (Reproduced from reference 65. Copyright 1990, American Chemical Society).

Figure 13. Multiple-varied receptors-macrobicyclic cyclidene with sites for metal ion and substrate top, sketch of ternary complex right, side view of substrate complex left, view into cavity that contains substrate. (Reproduced with permission from reference 69. Copyright 1989, Kluwer).

The hrst opticaUy active macrobicycles and macropolycycles were repotted by Lehn and co-woricers (187) in 1974. Employing the synthetic methodology developed in Strasbourg for the preparation of cryptands, chiral molecular receptors, such as (5)-191 and (5)-192, have been isolated and characterized. 

The macrobicycle 9 also binds NH4+, forming cryptate 24. The dynamic properties of 24 compared with 23 reflect the receptor-substrate binding complemen-... 

Lateral macrobicycles are dissymmetric by design thus, monoelectronic reduction of the Cu(ll) ion bound to the [12]-N2S2 macrocyclic subunit in the bis-Cu(ll) cryptate 45, gives a mixed valence Cu(i)-Cu(ll) complex [4.6]. Macrotricycle 46 forms a dinuclear Cu(ll) cryptate that acts as a dielectronic receptor and exchanges two electrons in a single electrochemical wave [4.7]. Complexes of type 47 combine a redox centre and a Lewis acid centre for the potential activation of a bound substrate [4.8]. 

The crystal structure 57 of the strong and selective complex formed by the terephthalate dianion with a hexaprotonated macrobicyclic polyamine shows that it is a molecular cryptate 56 with the dianion tightly enclosed in the cavity and held by formation of three hydrogen bonds between each carboxylate and the ammonium groups [4.19]. Both structures 53 and 57 illustrate nicely what supermolecules really are they show two covalently built molecules bound to each other by a set of non-covalent interactions to form a well-defined novel entity of supramolecular nature. Acyclic [4.20a,b] and macrobicyclic [4.20c] hydrogen bonding receptors... 

The medium may have a marked effect on the shape of receptor molecules itself. Shape modifications could strongly influence their substrate binding properties, for instance in the case of amphiphilic cyclophane receptors subjected to hydrophobic-hydrophilic factors in aqueous solution. Such medium effects in action are visualized by the solid state structures of two different forms of the water-soluble hexasodium salt of the macrobicyclic cyclophane 66, which could be crystallized in two very different shapes an inflated cage structure 71 building up cylinders disposed in a hexagonal array and a flattened structure 72 stacked in molecular layers separated by aqueous layers in a lamellar arrangement [4.73]. These two... 

A macrobicyclic thiazolium cyclophane 84 functions as a model of thiamine pyrophosphate-dependent ligases and effects benzoin condensations [5.38, 5.65a, A.l 1], Acyl transfer is catalysed by formation of a ternary complex between a cyclophane receptor and two substrates [5.65b]. 

Dietrich, B., Guilhem, J., Lehn, J.-M., Pascard, C., Sonveaux, E., 11. Molecular recognition in anion coordination chemistry. Structure, binding constants and receptor-substrate complementarity of a series of anion cryptates of a macrobicyclic receptor molecule. Helv. Chlm. Acta 1984, 67, 91-104. 

Lehn, J. M. Sonveaux, E. Willard, A. K. Molecular recognition. Anion cryptates of a macrobicyclic receptor molecule for linear triatomic species, J. Am. Chem. Soc. 1978,100, 4914-4916. 

The macrobicyclic ligand derived from 4,13-diaaza-18-crown-6 and Schiff-base spacer (e.g., 1,2-phenylenediamine or 1,2-ethylenediamine) forms stable lead(n) complexes of general formula [LPb(X)2 (solv),] in the presence of different counterions <2005IC5428>. The double protonation of the resulting compounds causes the demetalation of the complex without receptor destruction. Since this demetalation process is reversible and very fast, receptor L has been suggested as potential compound for lead(ll) extraction. 

The capping of both termini of three tridentate chelating units with covalent tripods provides highly rigid macrobicyclic receptors (i.e., cryptands), which are ideally suited for investigating variations of crystal-field parameters within isostructural series. Platas et al. (1999) have iso-... 

Undoubtly, cryptands remain the class of macrobicyclic and macropolycyclic receptors looking forward to a great future. The number of possible structures is practically unlimited and depends on a researcher imagination and creativity. Initially, the chemistry of cryptands had focused on the development of new synthetic strategies, either to improve the yields or to built up more complicated molecular architectures, like cylindrical, spherical or lateral macropolycycles, bi- or polynucleating, with hard and soft binding sites, etc. 

B. Dietrich, J. Guilhem, J.M. Lehn, C. Pascard, E. Sonveaux, Molecular Recognition in Anion Coordination Chemistry - Structure, Binding Constants and Receptor-Substrate Complimentarity of a Series of Anion Cryptates of a Macrobicyclic Receptor Molecule , Helv. Chim. Acta, 67,91 (1984)... 

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