Quantum chemical investigations on hydrogen bonding interactions established in the inclusion complex β-cyclodextrin/benzocaine through the DFT, AIM and NBO approaches
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Structure and stability of an inclusion complex formed by Benzocaine (BZC) and β-cyclodextrin (β-CD) were investigated computationally using different levels of theory. The conformational research based on PM6 method allowed reach two minimum-energy structures: model A and model B. The lowest conformers have been exposed to fully geometry optimization employing four DFT functionals: B3LYP, CAM-B3LYP, M05-2X and M06-2X. The performed DFT calculations have identified the model B, in which the amino group is located at the primary face of β-CD, as the most stable complex by an amount up to −40 kcal/mol. Further, the greater stabilization of model B in respect to model A, has been ascertained through AIM and NBO analyses which clarified the main hydrogen bonds HBs interactions governing the reactivity of BZC inside the hydrophobic cavity of β-CD. Finally, the estimated isotropic 1H nuclear magnetic shielding constants generated from the gauge-including-atomic-orbital calculation have been analyzed and then compared with the available experimental data.
KeywordsBenzocaine/β-cyclodextrin Hydrogen bond DFT AIM NBO GIAO
The authors would like to thank the General Direction of Scientific Research and Technological Development (DGRSDT) and the National Research Fund (FNR) for funding this work, through project PNR (8/u23/830).
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