Investigation of inclusion complexation of acetaminophen with pillar [5]arene: UV–Vis, NMR and quantum chemical study

Abstract

We have carried out combined experimental and density functional study on the complexation of acetaminophen and with pillar [5]arene. UV–Vis and NMR studies indicates the stoichiometry between acetaminophen and pillar [5]arene to be 1:1. The computed binding energy and the formation energy show the inclusion complex is stable, and its formation can occur at room temperature. The HOMO-LUMO gap for the inclusion complex is lower than the pristine pillar [5]arene and acetaminophen, which indicates that complex formation can be kinetically controllable. MESP and NBO analysis support the occurrence of charge transfer between the guest and host molecule. AIM analysis establishes the intermolecular bonds in the inclusion complex can be classified under a category with partially noncovalent and with a partial electrostatic in character. NCI isosurface displays blue patches due to H-bonding and green patches due to electrostatic interaction and is evenly distributed inside the pillar [5]arene, that could be responsible for the stabilization of the inclusion complex.