Theoretical Investigation of the Binding of Nucleobases to Cucurbiturils by Dispersion Corrected DFT Approaches.

The encapsulation of nucleobases inside CB7 has gained prominence due to its use as anticancer and antiviral drugs. With this respect, the nonconvalent interactions existing in the nucleobases encapsulated inside the CB7 cavity have been analyzed employing the dispersion corrected density functional theory. The CBn cavity has the ability to encapsulate two guest nucleobases molecules when they are aligned in parallel configuration. The computed association energy using the two- and three-body correction method computed at B3LYP-D3 level is close to the experimental estimate. The use of dispersion corrected DFs is essential to identify the correct binding energies. The solvation energy plays a vital role in the estimation of association energy. QTAIM analysis shows that the Laplacian of the charge density (∇2ρ) is negative and the presence of covalent interaction between the guest and host molecule. The NCI-RDG isosurface shows the presence of noncovalent intermolecular interactions such as van der Waals and hydrogen bonding. The existence of "splattering" of charges in guanine@CB7 molecule is responsible for its higher stability. From the AIM, NCI-RDG, and EDA results, we conclude that noncovalent and electrostatic interaction with partial covalent character exists in the intermolecular bonding between the host and the guest nucleobases. The ramification of such intermolecular bonds is reflected in the 1H NMR and 13NMR spectra.