E. Schollmeyer

New Textile Applications of Cyclodextrins

New areas of applications of cyclodextrins with textiles are possible. The abilityof cyclodextrins to form inclusion complexes can be used, e.g., to remove malodorfrom textile materials. The permanent fixation of cyclodextrins offers new textileswith interesting properties. Thus the formation of body odor is reduced by thecomplexation of the organic compounds of sweat. The release of perfumes fromcyclodextrins is possible by the use of textiles with fixed cyclodextrins. Pharmaceutical compounds are also set free in contact with the skin. Last but not least the analysis of the different compounds of the human sweat complexed by the cyclodextrins offers new possibilities in medical diagnostics.

Complexation of Some Amino Acids and Peptides by p-Sulfonatocalix[4]arene and Hexasodium p-Sulfonatocalix[6]arene in Aqueous Solution

The stability constants (log K), the reaction enthalpy(Δ H) and entropy (Δ S) of the complexesformed between some amino acids (glycine, L-alanine,L-valine, L-leucine, L-phenylalanine, L-tryptophan,L-threonine, and L-lysine) and peptides (glycyl-glycine,glycyl-L-alanine, glycyl-L-leucine, glycyl-L-phenylalanine,L-leucyl-glycine, L-leucyl-L-alanine, glycyl-L-valine,L-leucyl-glycyl-glycine, and glycyl-glycyl-glycine) withp-sulfonatocalix[4]arene and hexasodiump-sulfonatocalix[6]arene in aqueous solutions by meansof calorimetric titration have been investigated. The reportedresults demonstrate that the amino acids and peptides under studyform complexes with both p-sulfonatocalix[4]areneand hexasodium p-sulfonatocalix[6]arene. In the case of theamino acids and peptides the complexation with water-solublecalixarenes in aqueous solution is favored by enthalpiccontributions and disfavored by entropic contributions. However,no influence of the ring size of the calixarenes upon thecomplexation is observed. By comparison with the reaction ofthe sodium salt of phenol-4-sulfonic acid with amino acids amacrocyclic effect in case of the calixarenes is possible.

The Complexation of Amino Acids by Crown Ethers and Cryptands in Methanol

Complex formation between several crown ethers and the cryptand (222) and α-amino acids in methanol was studied by calorimetric titration. The ligand structure and the donor atoms of the ligands play an important role in determining the measured values of the reaction enthalpies and entropies. However, with the exception of the diaza crown ether (22) all stability constants are of the same order of magnitude. The enthalpic and entropic contributions to the stabilities of the complexes formed compensate each other. In methanolic solution the amino acids exist in their zwitterionic form. This equilibrium can be influenced. Under acidic, neutral or basic conditions different values of the reaction enthalpies are measured for the complexation of some amino acids with 18-crown-6. These results demonstrate that the concentration of the zwitterionic form of the α-amino acids can be influenced. Thus the reaction between macrocyclic and macrobicyclic ligands and amino acids should be described by at least two different reaction schemes.

Influence of ligand structure and solvent effects on complexation of neutral guests by several crown ethers

The formation of complexes between crown ethers and acetonitrile, chloroform, and nitromethane were investigated in carbon tetrachloride at 25°C. A significant influence of the ring size on the selectivity of the host is evident. The host 18-crown-6 forms complexes for which the reaction enthalpy and entropy are quite high. Host molecules with benzene side groups form complexes of lower reaction enthalpy and entropy and therefore the complexes formed are less stable than that of the analogous crown ethers without aromatic groups. Solvent effects on the stability constant K, the reaction enthalpy ΔH, and the reaction entropy ΔS were studied for the complexation of malonitrile by 18-crown-6. The reaction enthalpy and entropy values change in accordance with the dielectric constant of the solvent used, but no overall effect on complex stability with change in solvent dielectric constant was observed.

Complexation of Amino Acid Methylesters and Amino Alcohols by 18-Crown-6 and Benzo-18-crown-6 in Methanol

The complexation of protonated amino acid methylesters and amino alcohols bythe ligands 18-crown-6 (18C6) and benzo-18-crown-6 (B18C6) has been studiedin methanol using calorimetric titrations. No influence of the anions upon thestability constants and thermodynamic data for the reaction of protonated aminoacid methylesters with both ligands has been noticed, which indicates the completedissociation of the salts employed. A similar effect has been observed for thecomplexation of protonated and unprotonated amino alcohols with 18C6 andB18C6. The values obtained of the reaction enthalpies for the complexation ofprotonated amino acid methylesters with 18C6 are larger than those correspondingto the complexation with B18C6. The results demonstrate that the complex formationof unprotonated amino alcohols is favored by entropic contributions, while thecomplexation of protonated amino alcohols is favored by enthalpic contributionswith both ligands. The influence of various substituents on the complexation behaviorof amino acid and amino alcohol has also been investigated.