Host-guest interactions accompanying the cationic nitrogen heterocyclic guests encapsulation within pillar[5]arene: A theoretical research

Abstract

The formation of host-guest inclusion complexes by Pillar [5]arene (P [5]) and cationic nitrogen heterocyclic molecules were studied by DFT calculations at B3LYP-D3/6-311 + G** level, together with their equilibrium geometries, binding energies and electronic structures. MESP, NCI-RDG and AIM topography analysis were performed to explore underlying interactions. Geometric structures of inclusion complexes were changed compared with the individual molecules; MESP analysis revealed the driving force for the binding process; QTAIM and NCI-RDG methods were utilized to reveal the underlying non-covalent interactions. The inclusion complexes in 1:1 ratio were stabilized through weak C–H⋯O hydrogen bonds, C–H···π, π+···π and van der Waals interactions. The calculated electrophilic charge transfer indicated that charge flowed from P [5] to guests. Gibbs free energy accompanying the recognition process certified that formation of complexes were spontaneous and thermodynamically favorable.