Molecular Orbital Study on a Chlorine Anion Cryptate

Abstract

Closed shell LCAO-SCF-MO calculations were carried out for the chloride anion cryptate, which is of interest in connection with organic anion receptors and carriers. In the Cl- cryptate of [(C9H18)8(NH)2Cl]+Cl-, Cl-is encapsulated in the host molecule. Since the positions of the two protons bonded to the two nitrogens of the host molecule were not determined in the reported X-ray diffraction analyses, the positions of the two protons in the inclusion complex were decided by calculation using the ab initio molecular orbital method. A structure N+-H⋅⋅⋅Cl-⋅⋅⋅H-N+in which Cl-is in between the two nitrogens was most stable at values of r(NN) less than 7.0 A. The structure N+-H⋅⋅⋅Cl-⋅⋅⋅ H-N+was most stable at r(NN) = 6.023 Å. In the most stable structure, the two protons are covalently bonded to the two nitrogens. The structure obtained by geometry optimization for the two ammonium ions and Cl-was similar to that determined by X-ray diffraction analysis. © 1979, The Pharmaceutical Society of Japan. All rights reserved.