Inclusion complexes with iodide

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Other measures of nucleophilicity have been proposed. Brauman et al. studied Sn2 reactions in the gas phase and applied Marcus theory to obtain the intrinsic barriers of identity reactions. These quantities were interpreted as intrinsic nucleo-philicities. Streitwieser has shown that the reactivity of anionic nucleophiles toward methyl iodide in dimethylformamide (DMF) is correlated with the overall heat of reaction in the gas phase he concludes that bond strength and electron affinity are the important factors controlling nucleophilicity. The dominant role of the solvent in controlling nucleophilicity was shown by Parker, who found solvent effects on nucleophilic reactivity of many orders of magnitude. For example, most anions are more nucleophilic in DMF than in methanol by factors as large as 10, because they are less effectively shielded by solvation in the aprotic solvent. Liotta et al. have measured rates of substitution by anionic nucleophiles in acetonitrile solution containing a crown ether, which forms an inclusion complex with the cation (K ) of the nucleophile. These rates correlate with gas phase rates of the same nucleophiles, which, in this crown ether-acetonitrile system, are considered to be naked anions. The solvation of anionic nucleophiles is treated in Section 8.3. 

The s-triazines undergo chlorination at nitrogen to yield reactive N-chloro derivatives which oxidize iodide to iodine in the second step. This then forms an intense blue iodine-starch inclusion complex with starch. 

Primary and secondary amines and amides are first chlorinated at nitrogen by the chlorine released by the gradually decomposing calcium hypochlorite. Excess chlorine gas is then selectively reduced in the TLC layer by gaseous formaldehyde. The reactive chloramines produced in the chromatogram zones then oxidize iodide to iodine, which reacts with the starch to yield an intense blue iodine-starch inclusion complex. 

Substances containing active chlorine or bromine oxidize iodide ions — if necessary under the influence of UV light - to iodine, which reacts with starch to yield the well-known intense blue starch-iodine inclusion complex. 

Cyanine dye-CD complexes were first reported by Kasatani et al. in 1984 using 3,3 -diethyloxadicarbocyanine iodide (DODC) [22]. It was found that this dye formed complexes with (3- and y-CDs but not with a-CD. Later, they demonstrated the same tendency with cyanines 1 and 2 [23]. It was shown that inclusion of cyanine dyes in [i-CD and Me-(3-CD helps to inhibit dimer formation as well as to enhance the photostability of these cyanines, thereby enhancing the dyes utility as a fluorescent probe [7, 24],... 

When exposed to methyl iodide vapor at room temperature for 5 h, the crystalline powder of 1 d was changed into the 1 2 inclusion complex of 1 d with methyl iodide. 

Complexes 7-10 are dimerized through bridging of the terphenyl bound chromiums by the chlorides. For 9 and 10, the bridging chloride positions are contaminated with iodide due to its inclusion as a Lil impurity in the ArLi salt. The structures... 

The complexation of anionic species by tetra-bridged phosphorylated cavitands concerns mainly the work of Puddephatt et al. who described the selective complexation of halides by the tetra-copper and tetra-silver complexes of 2 (see Scheme 17). The complexes are size selective hosts for halide anions and it was demonstrated that in the copper complex, iodide is preferred over chloride. Iodide is large enough to bridge the four copper atoms but chloride is too small and can coordinate only to three of them to form the [2-Cu4(yU-Cl)4(yU3-Cl)] complex so that in a mixed iodide-chloride complex, iodide is preferentially encapsulated inside the cavity. In the [2-Ag4(//-Cl)4(yU4-Cl)] silver complex, the larger size of the Ag(I) atom allowed the inner chloride atom to bind with the four silver atoms. The X-ray crystal structure of the complexes revealed that one Y halide ion is encapsulated in the center of the cavity and bound to 3 copper atoms in [2-Cu4(//-Cl)4(//3-Cl)] (Y=C1) [45] or to 4 copper atoms in [2-Cu4(/U-Cl)4(/U4-I)] (Y=I) and to 4 silver atoms in [2-Ag4(/i-Cl)4(/i4-Cl)] [47]. NMR studies in solution of the inclusion process showed that multiple coordination types take place in the supramolecular complexes. 

The location of the cation in these canal compounds is not clear, but the cation definitely influences the nature of the crystal which is formed. With sodium and lithium iodides, a form II type of complex crystallizes as hexagonal plates. In the sodium iodide-iodine complex, the inclusion compound is not stoichiometric but rather the iodine atoms are packed into the canals in linear rows, with a spacing not related to the spacing of the dextrin molecules. 

The formation of these charged complexes in solution has been used as the basis for an electrophoretic separation of the Schardinger dextrins. Beckmann and Forster also found that complex formation with a-dextrin enhances approximately 2J- -fold the ultraviolet absorption maxima in iodine-iodide solutions at 290 and 350 m/i. It is probable that the colored complexes of iodine with methyl ethers and with the tosyl and mesyl esters of the Schardinger dextrins are also inclusion compounds of the same general type. 

Now follow several later synthetic methods, some of them of limited general application. 6-Azido-l,3-dimethylpyrimidine-2,4-dione (65), when refluxed with potassium carbonate in dimethylformamide, yielded 30% of 1,3-dimethyl-8-azapurine-2,6-dione. Inclusion of an alkyl halide in the reaction mixture gave an N-alkylated product (77% yield for methyl iodide, much less for other halides). The alkyl group was assigned to the 7 position without proof.Omission of the potassium carbonate gave the more complex molecule 66. ... 

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