Ternary inclusion complexes

Fig. 36 Anion inclusion in the [Cu2n(20)]2+ cryptate in aqueous solution. The stability of the ternary inclusion complex, expressed by log K for the equilibrium [Cun2(20)]4++ X- [Cun2(20)(X)]3+, at pH = 7 and 25 °C, is related to the bite length of the anion X-, with a sharp peak selectivity. The N3- ion has the right bite length to encompass the Cun-Cun distance, without inducing any serious conformational rearrangement of the dimetallic cryptate [73, 74]...

The monomer fluorescence of perylene, 23, in y-CD was quenched by iV,iV-dimethylaminoaniline (DMA) and by iV,iV-diethylaminoaniline. The formation of an exciplex emission, which was more intense in the presence of DMA, was observed. The new emission was concomitant with the red-shift and the broadening of the absorption spectrum. To maintain the solubility of 23, the solvent was an HjO/ethanol (7/3) mixture in which perylene forms a 1 1 1 complex with CD and alcohol addition of DMA causes the formation of the ternary complex y-CD-23-DMA, followed by association with the 1 1 complex y-CD-DMA to form a ternary inclusion complex 2 2 1 (CD-DMA-23) which deactivates by emitting exciplex fluorescence [137]. 

The structure of the ternary inclusion complex composed of 3-cyclodextrin, phenol, and, chloroform or carbon tetrachloride, formed in the reaction mixture, is determined by NMR spectroscopy. The selective catalysis by cyclodextrin was attributed to the regulation of molecular conformation of substrates with respect to dichlorocarbene, to trichloromethy1 cation, or to allyl cation in the ternary molecular complex. 

Figure 2. Time-averaged conformation of the binary and ternary inclusion complexes.

First, a ternary inclusion complex is formed from g-CyD, chloroform, and phenol or its derivative, in which the cavity of 3-CyD is largely occupied by chloroform. Phenol or its derivative in its anionic form penetrates shallowly in the cavity from the side involving the para carbon atom, since the inclusion of this apolar side in the apolar cavity is more favorable than the inclusion of the polar side... 

The ternary inclusion complex formation of allyl bromide, tri-methylphenol and CyD is probably favorable for the modified a-CyD, making para attack of the allyl cation effective. 

The ternary inclusion complex of indole, 3 CyD and dichlorocarbene is probably formed in the reaction mixture as shown in Fig. 7. Dichlorocarbene attacks at 3-position to yield indole-3-aldehyde. In the absence jjCyD, dichlorocarbene adds to 2,3- double bond of pyrrole ring. Then, the five-membered ring expands to six-membered ring, resulting 3-chloroquinoline. 3-CyD inhibits sterically the 2,3-double bond addition followed by ring-expansion. 

Formylations of phenol, resorcinol and indole, dichloromethylations of 4-methylphenol and 5,6,7,8-tetrahydro-2-naphthol, carboxylation of phenol, and allylation of 2,4,6-trimethylphenol proceed site-selec-tively in high yields by using 3-cyclodextrin as catalyst. The formation of ternary inclusion complex composed of cyclodextrin, substrate, and dichlorocarbene, trichloromethyl cation or allyl cation in the reaction mixture is an important factor of the site-selective reactions. The cyclodextrin is also effective by limiting the molecular size of the reaction intermediate. 

Great attention should be paid for the basic investigation and useful application of parent cyclodextrins themselves. Cyclodextrin can interact with two kinds of solutes A and B in water to form a a ternary inclusion complex, CD A B leading to specific condensation of two solutes to form... 

Scypinski and Cline Love [34] first proposed to use the ternary inclusion complex in which 1,2-dibromoethane was used as HA perturber to enhance phosphorescence of polyaromatic hydrocarbons. The author s group reported different systems for interested analytes j8-CD/l-naphthaleneacetic acid/1,2-dibromopropane [35,36], jS-CD/PAHs/epibromohydrin [37,38], and j -CD/7-methylquinoline/ bromocyclohexane [39]. 

Du et al. [61] reported that the fluorescence from naphthalene dimer could be easily observed in j -CD/Naph or j -CD/Naph/a-BrN. When n-butanol was added as the fourth component to ternary inclusion complex, the dimer emission almost disappears accompanying remarkable enhancement in the RTF from a-BrN in quarternary inclusion complex j -CD/Naph/a-BrN/n-butanol. 

In another study, it was successfully reported an intimate ternary blend system of poly(carbonate) (PC)/poly(methyl methacrylate ) (PMMA)/poly (vinyl acetate) (PVAc) obtained by the simultaneous coalescence of the three guest polymers from their common y-cyclodextrin (y-CD) inclusion complex (IC). The thermal transitions and the homogeneity of the coalesced ternary blend were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) [50]... 

FIGURE 1 Molecular structures of I, II, and a-cyclodextrin (a-CD) alkoxide. Schematic representation of the inclusion complexes and reaction intermediates involved in the hydrolysis of I affording acetic acid and m-ferf-butyl phenol. The inset shows the CAChe-minimized structure of the ternary catalytic complex I C a-CD alkoxide-ll proposed by Bender et al. (7S). The putative hydrogen bond between the alkoxide of a-CD and II is indicated by a solid line. a-CD alkoxide is shown in stick representation, and only polar hydrogen atoms are specified. I is shown in CPK representation and II in ball and stick. (See Color Insert in the back of this book.)... 

For CyD complexes a number of stoichiometric ratios has been observed [2]. The most commonly reported ratios are H G = 1 1 and H G = 2 1. However, other stoichiometries as well as ternary CyD-containing complexes [47] are known. An example of 2 1 stoichiometry is the camphor-a-CyD complex in which the guest molecule is embedded inside a capsule formed by two host molecules [48]. Fenbu-fen (y-oxo-[l,l -biphenyl]-4-butanoic acid) is an interesting example of a compound which shows stoichiometry dependence on the CyD cavity size. It does not form an inclusion complex with a-CyD, but displays H G = 1 1 stoichiometry with f-CyD and H G = 1 2 stoichiometry with y-CyD [49, 50]. Metoprolol is another such compound which forms 1 1 complexes with a-CyD and f-CyD but with y-CyD it forms an H G = 1 2 complex [51]. A similar phenomenon detected using HPLC for a complex with a first-generation dendrimer is presented in Chapter 5 [52]. On the other hand, 1-adamantanecarboxylic acid and f-CyD form a complex with temperature-dependent stoichiometry, H G = 1 1 at 25 °C and H G = 1 2 at 0 °C [28]. For the complexation of dodecyltrimethylammonium bromide with a-CyD two competing associations with stoichiometries of H G = 1 1 and H G = 2 1 have been reported [53]. Use of the method of continuous variations in such situations becomes questionable and information about the complex stoichiometry is revealed directly from the titration measurement described in Section 9.2.3. 

Like CD-based hydrogels, CB[/i]-derived hydrogels can also be divided into different classes (1) hydrogels that consist of a three-component system cross-linked by ternary CB[8] inclusion complexes and (2) hydrogels based on a two-component system of CB[6] alkylammonium ion host-guest pairs. At least one example of each hydrogel class is described. 

Supramolecular spherical assemblies of NPs with photoresponsive adhesion/dispersal behaviour were also obtained in a ternary system hierarchically combining the host-guest interaction of different types of CDs toward porphyrin and azobenzene. The inclusion complexation of an azobenzene modified water soluble porphyrin (1) with phthalo-cyanine-grafted permethyl (3-CDs (2) could be reversibly cross-linked to relatively larger nanospheres with naphthyl bridged bis(a-CD)s (3). The large spheres (12 -3) turned reversibly to small-sized particles (1 2) upon photoisomerization of the azoaromatic group in 1 (Fig. 13). 

CyS-A was expected to form a binary inclusion complex with acetone and also ternary complexes with acetone and the guest molecules examined, but no acetone peak was detected in chromatograms of lyophilized reaction mixtures. There was no acetone even in the sample prepared by stirring CyS-A with acetone or acetone solution of drugs, followed by filtration and drying in air. 

A non-covalent sensory system based on phosphorescence was also described recently. The inclusion complex of 1-bromonaphthalene with p-cyclodextrin (58) shows room temperature phosphorescence in the presence of menthol enantiomers, due to the formatiOTi of ternary complexes with both menthol and 1-bromonaphthalene included. The phosphorescence lifetime was found to be different for the two enantiomers (4.28 0.06 and 3.71 0.06 ms for (—)-menthol and (-F)-menthol, respectively) due to the higher exposure to dissolved oxygen of the latter complex [123]. 

The ultimate goal of the surface complexation modeling approach is to provide users with databases, which can be applied without significant restrictions in predictive modeling. The application would certainly be limited to cases for which the dominating sorbent phases and the relevant solution compositions are known and for which significant ternary surface complex formation, which was not experimentally studied, is not expected. The inclusion of ternary surface complexes would require a very extensive database (cf. subsections on ternary surface complexes). 

In bicomponent system consisting of CD and luminophor, ternary or more grade inclusion complex is possible [28]. For example, Brewster et al. [29]... 

The synergetic interaction or effect exists widely in various scientific and technical fields. In terms of CD-induced room temperature phosphorescence it can be defined as the principal factor(s) and secondary factor(s) affecting the characteristic properties, e.g., spectrum, quantum yield, lifetime and anisotropy, of the system concerned match automatically with each other to reach an optimization state, and cause remarkable change in the properties. The third or both third and fourth components added to the system interested form ternary or higher inclusion complex together with the CD and phosphore, and they synergetically enhance the stability of triplet states of inclusion complex, leading to increase the phosphorescent intensity or lifetime. 

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