Encapsulation cations

Langmuir-Blodgett films, 36 195-197 Langmuir monolayers, 36 192-195 phospholipid vesicles, 36 182-187 encapsulated cations, 36 183-184... 

Texaphyrin, (II), (4), has a central core that is 20% larger than porphyrin. It has been prepared to encapsulate cations considerably larger than porphyrin containable counterpart. 

The second class of dinuclear Cu —Cu complexes is represented by several cascade complexes, in which a pair of cations is encapsulated within a cryptand host (XVII-XIX), with a bridging CN ligand spanning the space between the cations. In these cases, the dinuclear complex is stabilized due to the encapsulated cations rather than by the cyanide bridge. Lu et al., (78) reported a product of this type, [Cu°2(XVII)(CN)](C104)3 (Fig. 9), as a result of the unexpected C C bond cleavage of acetonitrile in the presence of [Cu 2(XVII)]( 104)4. These authors established that the reaction rate exhibits a first-order dependence... 

Binding of cations inside the host molecular cavity is not common but has been demonstrated in the solid state for organometallic cations. There are a small number of examples of cation capture within capsule-like assemblies. Deprotonated CTC forms clam-like capsule arrangement from hydrogen-bonding interactions between the CTC molecules. Encapsulated cationic guests include... 

Figure 4 Crystal structures of clam-like CTC dimers encapsulating cations, with O O consistent with hydrogen bonding shown as dashed lines, (a) Rb" complex (b) NEt4+ complex with only one of two disordered positions of the cation shown.

The ditopic crown ether-amide caging hgand 256, prepared in [180], co-encapsulates cationic and anionic species by Scheme 2.159. This hgand transports NaCl, KCl, NaBr, and KBr salts from their aqueous solutions through a liquid organic membrane with the selectivity changing in a row K > Na > Li. The selectivity order is reversed when this covalent capsule extracts solid alkah metal chlorides and bromides into organic phases [180],... 

Expanded bis-calix[4]arene homo- and het-erodimeric capsules 346-348 have been self-assembled in [27] from an appropriate ligand syntones 136 and 137 by Scheme 3.26. As follows from NMR, CIS, and UV-vis data, the ligand 348 forms 1 1 cage complexes with encapsulated cationic guests. 

Self-assembled hexaresorcinarene capsules 397 and 398 (Scheme 3.71) have been used in [70] as potent hosts for paramagnetic nitroxide spin probes (e.g., the derivatives of tempo). According to EPR data, they encapsulate cationic and amine nitroxide guests, which are complementary to the mostly aromatic inner cavities of these caging ligands, but discriminate 0x0- and hydroxyl-functionalized nitroxides [70]. 

We met the synthetic ionophores, the crown ethers, in Section 4.3.3 these not only act as PT catalysts to transfer ions into organic media but also encapsulate cations, and hence break up ion pairs. Naked, unpartnered, ions are much more reactive . Potassium permanganate is insoluble in benzene, so if an aqueous solution of K[Mn04] is shaken with benzene, there is no color in the organic layer. However, when 18-crown-6 (18-C-6 is the appropriate size to coordinate IC)... 

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