Structure Elucidation of Benzhexol-<i>β</i>-Cyclodextrin Complex in Aqueous Medium by ¹H NMR Spectroscopic and Computational Methods

Abstract

Complexation of benzhexol and <i>β</i>-cyclodextrin was studied in aqueous medium. The formation of inclusion complex and its stoichiometry were determined by NMR titration method. ROESY spec-trum, recorded with a mixing time of 0.5 s in few minutes, displayed crosspeaks between phenyl ring of benzhexol and <i>β</i>-cyclodextrin cavity protons established the inclusion of phenyl ring into the cavity. No inference about the distances between interacting protons could be drawn due to spin diffusion. However, analysis of peak intensity ratios of intermolecular crosspeaks suggested partial penetration of phenyl ring from wider side. Molecular mechanics studies supported these conclusions and the lowest energy conformation was proposed as the probable structure of 1:1 benzhexol-<i>β</i>-cyclodextrin complex.