engleski

NMR spectroscopy and thermodynamics of supramolecular host-guest reactions ; calixarenes and cyclodextrins

The lecture will be dedicated to the role of NMR spectroscopy in the physico-chemical investigations of host-guest complexation reactions, namely the complexation of alkali- metal cations with calix[4]arenes, and the inclusion of lipophilic moieties within hydrophobic cavity of cyclodextrins. In the first part of the lecture, comprehensive investigations of calix[4]arene complexation reactions in several solvents will be described. The thermodynamic data (complex stability constants and derived standard reaction Gibbs energies, reaction enthalpies and entropies) determined by various experimental methods will be correlated with the results of structural investigations. The solvation effects on the equilibria of binding reactions will be discussed in detail. For that purpose, thermodynamic cycles involving the reactant and the complex transfers will be prepared and explained. The role of NMR spectroscopy in revealing specific solvation effects, which can influence the complexation equilibria remarkably, will be addressed. In the second part of the lecture, the thermodynamics of various guest inclusion within the nonpolar cavity of cyclodextrins in several strongly hydrogen-bonding solvents will be reviewed. The influence of the guest structure, size, and conformational freedom on the complex stability will be discussed. The effect of temperature and solvent on the complexation reactions will be analysed in detail. The importance of NMR investigations for the rationalization of the corresponding thermodynamic complexation parameters will be revealed. Finally, the thermodynamics of solvophobically driven complexation involving non-polar solutes and cyclodextrins in organic solvents and water will be addressed.

calixarene ; cyclodextrin ; complexes ; NMR ; thermodynamics ; solvation

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