A DFT study on the geometry, tautomerism and noncovalent interactions of the Mepivacaine drug with the pristine SWCNT and -COOH functionalized SWCNT

The Mepivacaine drug is used as a local anesthetic in dentistry, which could exist as three different tautomers. Herein, geometry, energy behavior as well as tautomerization of these tautomers have been investigated by employing density functional theory (DFT) and considering the solvent effects with the polarizable continuum model (PCM) model. The most stable tautomer of the Mepivacaine has a carbonyl and an -NH amine groups in its structure. The frontier orbitals and the energy gap of the molecule have been computed using the natural bond orbital analysis (NBO). Also, the armchair (5,5) single wall carbon nanotube (SWCNT) was used for investigation of the noncovalent interactions of the Mepivacaine molecule with the pristine SWCNT and the -COOH functionalized SWCNT in several forms. Geometries of the possible forms have been optimized. The most stable form for noncovalent interactions of the drug with each of the pristine and functionalized SWCNTs have been determined. The intermolecular H-bonds have essential role in energy behavior of the noncovalent interactions between the Mepivacaine drug and the investigated SWCNTs.