Theoretical study on the adsorption of benzylpenicillin molecule onto vermiculite surface

Abstract

Two stable configurationss (P1 and P2) formed by interaction of benzylpenicillin molecule with vermiculite surface are obtained on the potential energy surface. The adsorption energies of P1 and P2 complexes are significantly negative at ca. -58 and -47 kcal.mol⁻¹, respectively. The adhesion of benzylpenicillin on vermiculite surface is favorable via >C = O...Mg interactions and O-H…O hydrogen bonds between -COOH group of the molecule with Mg²⁺ and O²⁻ ions on the surface. Notably, the benzylpenicilline molecule is adsorbed favorably onto vermiculite surface at Mg²⁺ site binding to O²⁻ ions in -SiO₃ group as compared to that in -AIO₃ group. It is found that stability of P1 and P2 is contributed by both >C=O...Mg and O-H...O interactions. Remarkably, the electron density transfer from the surface to the molecule is slightly stronger than that from molecule to surface. Calculated results indicate that the adsorption of benzylpenicillin on vermiculite surface is regarded as a strong chemisorption process.