THE INFLUENCE OF STRUCTURAL EFFECTS ON THE COMPLEXING ABILITY OF CROWN ETHERS

Abstract

Simple regression including interaction energies of the cation-ligand systems explains to some extent the variability in logarithms of stability constants of complexes formed by a series of nine 18-crown-6 ethers with potassium cations in methanol. The atomic charges were calculated for energy minimized structures, found during molecular dynamics computations. In order to mimic the residual solvation of complexed cations, two CH₃OH molecules were incorporated above and below the macrocyclic plane. Polarization effects of the metal cation on the resulting atomic charges were considered in calculations and found to be crucial for satisfactory correlations with experimental data.

Key Words:

• Crown ether complexes
• stability constants
• structural effects
• molecular dynamics