Experimental and theoretical investigation on the structural characterization and orientation preferences of 2-hydroxy-1-naphthoic acid/β-cyclodextrin host-guest inclusion complex

The inclusion complex formation between 2-hydroxy-1-naphthoic acid (2H1NA) and beta-cycloclextrin (beta-CD) in liquid, solid and virtual states was investigated. The binding constant of 2H1NA:beta-CD complex is estimated in liquid state using cyclic voltammetry (CV) analysis at pH 2.75. Drastic increase in the anodic peak current and peak potential with the increase in beta-CD concentration is attributed to the inclusion complex formation between beta-CD and 2H1NA. The diffusion coefficient, and the electron transfer rate constant (k(o)) of the 2H1NA:beta-CD complex are also estimated using CV studies. The solid 2H1NA:beta-CD complex prepared by co-precipitation method is characterized by FUR, and NMR techniques. The estimated stabilization energies, E-HOMO-E-LUMO, and MEP maps of complexes infer that guest molecule prefers the orientation in which it experiences lesser steric repulsion effect and scores as a highly stable and energetically favourable. Results of computational studies, semiempirical analysis and experimental investigations correlate well with each other. (C) 2016 Elsevier B.V. All rights reserved.