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Science, Algeria

Benghodbane S.,Annaba University | Khatmi D.,Guelmas University
Comptes Rendus Chimie | Year: 2012

The geometry of the inclusion complexes of 2-O-methyl-beta-cyclodextrin (called MeβCD or Crysmeb) with the two tautomers (enol and keto) isomer of doxycycline (DOX) in the gas phase, is determined using PM6 and ONIOM2 calculations with [B3LYP/6-31G(d):HF/3-21G*] level. Inclusion process pathways are described and the most probable structure of the 1:1 complex is sought through a potential energy scan using the PM6 method. Within the ONIOM2 procedure two levels of calculation are defined: B3LYP/6-31G(d) for DOX and the HF/3-21G* level for Meβ CD. The geometry of the most stable complex in the keto or enol forms obtained with the two methods, in which the aromatic ring is included inside the hydrophobic cavity of Crysmeb. The energetic differences between the two forms are 0.17 and 6.27 kcal/mol, respectively with PM6 and [B3LYP/6-31G(d):HF/3-21G*] calculations. These energies also include ZPE corrections. The energetically more favorable structure obtained with the ONIOM2 method leads to the formation of six intermolecular H-bonds between DOX and Crysmeb, i.e. three conventional H-bonds, one between the oxygen atom (O197) of the OH bond of DOX and the hydrogen atom (H140) of Crysmeb and the second between oxygen atom (O53) and a hydrogen atom (H218) of the hydroxyl group of DOX. The last one is between the oxygen atom (O73) and a hydrogen atom (H214) of the hydroxyl group of DOX. These H-bond are assisted by three weak H-bonds of type (C-H⋯O). All these interactions were investigated using the Natural Bond Orbital (NBO) approach. © 2012 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved. Source


Benghodbane S.,Annaba University | Khatmi D.,Guelmas University
Journal of Inclusion Phenomena and Macrocyclic Chemistry | Year: 2013

A computational study of inclusion complexes of 2-methyl-βCD with Doxycycline tautomeric (enol and keto form) has been performed with several combinations of ONIOM hybrid calculations. The reliability of the ONIOM2 calculations at the integrated level, ONIOM2 (M05-2X/6-31G(d): M05-2X/3-21G*), ONIOM2 (M05-2X/6-31G(d):HF/3-21G*), ONIOM2 (B3LYP/6-31G(d):HF/3-21G*), ONIOM2 (B3LYP/6-31G(d):B3LYP/3-21G*) and ONIOM2 (B3PW91/6-31G(d):B3PW91/3-21G*) was examined. Their complexation, binding, deformation and stabilization energies, and geometrical data were compared with those of the target geometry structure optimized at the M05-2X/6-31G(d) level of theory. Mixed combinations ONIOM2 (M05-2X 6-31G(d):HF 3-21G*) and ONIOM2 (B3LYP 6-31G(d):HF 3-21G*) reproduces nearly the target geometry structure and provides realistic energetic results at a relatively low computational cost. © Springer Science+Business Media B.V. 2012. Source


Mallem N.,Annaba University | Khatmi D.,Guelmas University | Azzouz S.,Annaba University | Benghodbane S.,Annaba University | Yahia O.A.,Annaba University
Journal of Inclusion Phenomena and Macrocyclic Chemistry | Year: 2012

[M05-2X/6-31G :PM3MM] and [B3LYP/6-31G :PM3] ONIOM2 methods have been used to investigate the vitamin A propionate/β cyclodextrin complex with 1:2 stoichiometry. Both methods give almost the same lowest energy minimum. The minimum energy structure of the complex is found in good agreement with experimental data. In this configuration, the major structure of propionate of vitamin A (PVA) is embedded inside the two cavities of βCD while the propionate group is kept outside. However, the three methyl groups of PVA are positioned in the free space between both βCD molecules. The driving forces for complexation are dominated by Van der Waals interactions between PVA and the βCD molecules assisted with multiple hydrogen bond interactions between the two cyclodextrin molecules. These interactions were investigated using the natural bond orbital approach. © 2011 Springer Science+Business Media B.V. Source


Djemil R.,Guelmas University | Khatmi D.,Guelmas University
Canadian Journal of Chemistry | Year: 2011

The inclusion process involving β-cyclodextrin (β-CD) with dopamine (DA) was investigated by using PM6, HF, and ONIOM methods. The most stable structure was obtained at the optimum position and angle. The complex orientation in which the catechol ring of dopamine penetrates into the β-CD cavity near primary hydroxyls is preferred in energy. The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital analysis, employed to quantify the donor-acceptor interactions between dopamine and β-CD. A study of these complexes in solution was carried out using the CPCM model to examine the influence of solvation on the stability of the dopamine β-CD complex. © 2011 Published by NRC Research Press. Source


Djemil R.,Guelmas University | Khatmi D.,Guelmas University
Journal of Computational and Theoretical Nanoscience | Year: 2012

The structural aspects for complexation of dopamine (DA) and epinephrine (EP) to β-CD were explored by using PM6, HF and ONIOM methods. The most stable structure was obtained at the optimum position and angle. The complex orientation in which the catechol ring of the guest penetrates into β-CD cavity near primary hydroxyls is preferred in energy. The inclusion complex of DA with β-CD is more stable than that of EP. The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of NBO analysis employed to quantify the donor-acceptor interactions between the guest molecules and β-CD. Copyright © 2012 American Scientific Publishers All rights reserved. Source

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