Unraveling the binding nature of hexane with quinone functionalized pillar[5]quinone: a computational study

The nature of host-guest interactions between the hexane and pillar[5]arene and its quinone modified pillararenes has been studied using dispersion-corrected density functional theory and wave functional methods. The introduction of quinone in pillararene prompted flexibility in structure and the electrophilicity of pillararenes increases with the number of quinone moiety. Thermochemical as well as energetic results indicate that hexane binding is favorable on all studied systems. The presence of quinone reduces the exothermicity, and exergonic nature and the decrease in temperature increases the free energy of formation. Molecular electrostatic potential analysis indicates the existence of charge transfer between the host and guest molecules. Quantum theory of atoms in molecule analysis reveals in the quinone functionalized pillararenes, the number of interactions arising from quinone is less than that on the 1,4-alkoxybenzene unit. Noncovalent interaction analysis shows a larger area of interactions correspond to C-H center dot center dot center dot pi interactions in the encapsulated complexes. EDA results reveal that dispersion Delta E-disp interaction followed by electrostatic attraction Delta E-elstat contributes mainly for the attractive terms. These insights can be used to tune further and improve the binding ability of pillararene guest towards linear host molecules.