engleski

Hydrogen Bonding and Solvent Effects on Calixarene Coordination Reactions

Calixarenes are macrocyclic compounds comprising phenolic units ortho-linked by methylene bridges. Many calixarene derivatives are known to be very efficient and in some cases selective binders of ions and neutral molecules. Our group has been extensively investigating the complexation reactions of calix[4]arene derivatives in several solvents by means of an integrated thermodynamic, structural, and computational approach. The solvents were chosen taking into account the differences in their cation (anion) and ligand solvation abilities and the possibility of ligand-solvent and complex- solvent hydrogen bonding. The thermodynamic data (complex stability constants and derived reaction Gibbs energies, reaction enthalpies and entropies), determined using several experimental techniques, were correlated with the structural results obtained by X-ray crystallography, NMR, and computational methods (DFT and molecular dynamics). The solvation and transfer parameters of the ligands and their complexes were also determined and discussed. The intra- and intermolecular hydrogen bonding and solvent effects (especially specific solvent-solute interactions) on the equilibria of the binding reactions were particularly addressed. The results of the above-mentioned studies clearly indicates how remarkable and complex the influence of the solvent on the ion-hosting abilities of the calixarene derivatives, and macrocycles in general, can be. They also suggest that the integrated and comprehensive experimental and computational investigations can indeed provide a rather detailed insight into the ligand properties and reactivities, i.e. the factors governing the complexation processes.

calixarenes ; complexation ; hydrogen bonding ; solvation ; thermodynamics

Special Issue of Bulletin of the Chemists and Technologists of Bosnia and Herzegovina