A density functional theory study on complexation processes and intermolecular interactions of triptycene-derived oxacalixarenes

Abstract

Triptycene-derived oxacalixarenes (TP) exhibit two different conformations: cis-isomer (TPA) and trans-isomer (TPB). The geometries structures were optimized by the density functional theory (DFT) based on ωB97XD and B3LYP-D3 functionals. The oxacalixarenes favor the inclusion complex through noncovalent interactions, such as hydrogen bonding, π···π stacking, and C–H···π interactions. The formation of a inclusion complex is spontaneous and thermodynamically favorable. The calculated 1H nuclear magnetic resonance (1HNMR) spectrum of MV2+@TPA (MV2+: methyl viologen cation) showed the chemical shifts of its protons have changed upon complexation. The frontier molecular orbitals and the energy of band gap were constructed and analyzed. The interaction between host and guest was investigated and characterized by the molecular electrostatic potential (MESP), vibration frequency, the natural bond orbital (NBO), and quantum theory of atoms in molecules (AIM) methods. And also the reduced density gradient (RDG) isosurface map and scatter diagram reflected the location and intensity of the noncovalent interactions.