Cations neutral molecules, simultaneous binding

The earliest reported examples of a system binding cations and neutral molecules simultaneously employed traditional inacrocyclic host molecules, such as calixarenes 1, which are described more fully below, and cyclic polyethers. Incorporating pyridyl or Schiff base groups into crown ethers leads to macrocycles with two possible binding modes. "" in the complex 2,6-pyrido[27]crown-9.LiC104.urea, both the Li" cation and urea are encapsulated within the crown ether cavity with interactions between them. In contrast, the complex of a Schiff-base-derived crown ether 2 has the Ni immobilized at the Schiff-base binding sites in a square-planar geometry. 

Cation-n Interactions, p. 214 Crown Ethers, p. 326 Fluorescent Sensors, p. 572 lonophores, p. 760 Organic Zeolites, p. 996 Platonic and Archimedean Solids, p. 1100 Protein Supramolecular Chemistry, p. 1161 Simultaneous Binding of Cations and Neutral Molecules, p. 1295... 

Inelastic Neutron Scattering, p. Ill Isostructurality of Inclusion Compounds, p. 767 The Lock and Key Principle, p. 809 Macrocycle Synthesis, p. 830 Molecular Wires, p. 925 Self-Assembling Capsules, p. 1231 Simultaneous Binding of Cations and Anions, p. 129i Simultaneous Binding of Cations and Neutral Molecules, p. 1295... 

The simultaneous binding of cations and neutral molecules can be achieved by different types of molecular hosts or assemblies. Traditional host molecules such as crown ethers and calixarenes can complex both a cation and neutral molecule within different receptor sites. Metallohosts, where a metal cation is an intrinsic part of the host assembly, can complex neutral molecules within... 

Verboom. W. Reinhoudt, D.N. Simultaneous Binding of Cations and Neutral Molecules. In Comprehensive Supra-molecular Chemistry Atwood. J.L.. Davies. J.E.D.. MacNichoL D.D.. Vbgtle, F.. Eds. Pergamon Oxford, 1996 Vol. 2. 495-517. 

Cyclophano-crown ether host (Scheme 8), possessing cyclic polyether and cyclophane moieties in a single molecule and ability to simultaneously bind a potassium cation and 6-methoxy-2-naphthonitrile in a water-methanol mixture, is of particular interest, since the contrasting solvent effects can be examined in the same host. Indeed, neutral 6-methoxy-2-naphthonitrile guest forms a 160-fold more stable complex with the cyclophane moiety in more hydrophilic 60 40 water-methanol solvent than in pnre methanol. In contrast, the affinity toward potassium ion is enhanced by a factor of 120 in pure methanol rather than in 60 40 water-methanol. Scheme 8... 

Resorcinarenes, which are closely related to caUxarenes in terms of sfructure, are attractive building blocks for a variety of supramolecular architectures owing to then-ability to bind neutral and cationic molecules inside their electron-rich cavity and simultaneously to form multiple hydrogen bonds with the eight hydroxylic groups of the upper rim of the molecule. Resorcinarenes are known to form dimeric and hexameric hydrogen bonded spherical assembUes and act as supramolecular hosts for smaller molecules. ... 

At a neutral or positive surface, the competitive adsorption of the two molecules becomes dependent on the coadsorbed Cl ion concentration. With decreasing the KCl concentration to 0.01 M a decreasing in the intensity of CPC modes at 1030 cm and 1626 cm" is observed. Simultaneously, new bands at 848 cm" and 1582 cm" develop, and this is ascribed to the corresponding vibrations of adsorbed nitropheno-late ions (cf. Fig. 9). Therefore, the coadsorbed halide ions are very important for the binding of cationic surfactants and organic pollutants in the first adsorption layer. 

---