Host–guest interaction between 3,4-dihydroisoquinoline-2(1H)-sulfonamide and β-cyclodextrin: Spectroscopic and molecular modeling studies

Abstract The inclusion complex of 3,4-dihydroisoquinoline-2(1 H )-sulfonamide with β-cyclodextrin was investigated experimentally and by molecular modeling studies. The stoichiometric ratio of the complex was found to be 1:1 and the stability constant was evaluated using the Benesi–Hildebrand equation. Estimation of the thermodynamic parameters of the inclusion complex in vacuum showed that it is an enthalpy driven process phase and an enthalpy–entropy co-driven process in aqueous solution, which is in accord with the experimental results. Semi-empirical calculations using PM3, PM6 and ONIOM2 methods, in vacuum and in water, were performed. The energetically more favorable structure obtained with the ONIOM2 method leads to the formation of intermolecular hydrogen bonds between sulfonamide and β-cyclodextrin. These interactions were investigated using the Natural Bond Orbital (NBO).