Investigation of intermolecular interactions in inclusion complexes o pyroquilon with cucurbit[n]urils (n=7,8) using DFT-D3 correction dispersion

In this work, the host-guest inclusion complexes of pyroquilon (Pyn) with two cucurbit[n]urils (CB[7] and CB[8]) were investigated by the density functional theory including dispersion correction (DFT-D3) method using the following functional, B3LYP and M06-2X with the split valence double zeta 6-31G(d) basis set in both gas and aqueous phases. The geometries of these complexes were optimized and the results were analyzed and compared. To provide insights into the contributions of different components of interaction energy of studied complexes, we used the energy decomposition analysis (EDA) which provides quantitative interpretation of chemical bonds. HOMO and LUMO energies, the global chemical reactivity descriptors and Fukui function were computed. The absorption spectra of the complexes have been calculated using TD-DFT method. Molecular electrostatic potential was calculated to predict the reactive sites for electrophilic and nucleophilic attack. The study of the type of the interaction between the pyroquilon molecule and the two hosts is better explained using the non-covalent interaction-reduced density gradient (NCI-RDG). AIM analyses demonstrate the establishment of conventional H-bond interaction. The H-1 nuclear magnetic resonance (H-1 NMR) chemical shift of the complexes was studied using the Gauge-Including Atomic Orbital (GIAO) method and compared with experimental data. It has been shown that hydrogen bond energies from the QTAIM theory correlate well with the H-1 NMR chemical shifts calculated. (C) 2020 Published by Elsevier B.V.