Electronic Structure and H-Bond Interactions in <I>β</I>-Cyclodextrin/Piroxicam Complex

Abstract

A spatial configuration of the inclusion complex formed between -cyclodextrin and piroxicam has been proposed based on the ONIOM2 [HF/3.21G * :B3LYP/6.31G(d)] calculation. In the favorable configuration (namely P -orientation) the pyridine ring is totally embedded in the cyclodextrin cavity while the aromatic ring remains outside the cavity. This configuration is more favorable of 23.43 kcal/mol, comparing to the configuration in which the pyridine ring is localized outside the cavity (namely B-orientation). In order to take solvent effect into account, DFT (B3LYP/6-31G(d)) calculations using Onsager and two polarizable continuum models, CPCM and IEFPCM were carried out. The Onsager model, CPCM and IEFPCM gives P -orientation more favorable respectively of 25.71 8.26 and 8.46 kcal/mol. The geometry of the energy minima (P -orientation) leads to the formation of eight intermolecular hydrogen bonds between piroxicam and CD: Three conventional H-bonds (X H· · · O) and five weak H-bonds (C H· · · O). These interactions were investigated by Natural Bond Orbital (NBO) approach.

Driving forces and electronic structure in β-cyclodextrin/3,3′-diaminodiphenylsulphone complex

“…For that, we choose the following levels of Finally the natural bond orbital (NBO) analyses were applied as a powerful approach for the evaluation of the intermolecular interactions between β-CD and 3DADPS molecules. The natural bonding orbital (NBO) calculations were performed using NBO 3.1 program as implemented in the Gaussian 03 package in order to understand various second order interactions between the filled orbitals of one subsystem and vacant orbitals of another subsystem, which is a measure of the intermolecular delocalization on hyperconjugation [25][26][27]. …”

“…In terms of the NBO approach [27] this is expressed by means of the second order perturbation interaction energy E (2) involving neighboring orbitals. The selected electron donor orbital, electron acceptor orbital and their corresponding second-order interaction energies of the E (2) indicate the intensity of the interaction between the electron donor and electron acceptor orbital.…”

Analysis of Electromagnetic Absorption Properties of Multilayer Structure of Alternating Fe Ferromagnetic and SiO<SUB>2</SUB> Nanofilms

“…These research have provided ample theoretical foundation for example in the Refs. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], but the experimental results about EM absorbing capability of metal nanofilm have never been openly reported before. In the paper, the Fe/SiO 2 films have been successfully designed and prepared by electron beam vapor deposition and their electromagnetic scattering properties have been analyzed in a series of experiments.…”