PNNL

Abstract

An extensive conformational search of 15-crown-5 complexes with the alkali and alkaline earth cations was performed with an extended MM3 force field. A detailed comparison of the search results with crystallographic data establishes that the model accurately predicts the structural features of these compounds. An improved method is reported for scanning a macrocycle conformer cavity to determine the preferred metal ion size. We demonstrate that the variations in ligand strain for different conformers as a function of metal size rationalize the crystallographically observed variations in 15-crown-5 conformation as a function of metal ion size and charge.