DFT/NBO Analysis of Interaction between 4-hydroxycoumarin and Single Walled Carbon Nanotubes in Pistachio

Fruits, vegetables, oils, coffee, nuts, and tea contain coumarin. The scientific attraction of coumarins is attributed to their pharmacological activity. In this study, density functional theory (DFT) calculations were performed  in the B3LYP/6-31G(d) level of theory to evaluate the potentialities of single-walled carbon nanotubes (SWCNT) as a carrier for 3-acetyl-6-methyl-4-hydroxy-coumarin. The natural bond orbital (NBO) analysis suggested that the functionalized nanotube plays the role of an electron donor and 3-acetyl-6-methyl -4-hydroxy- coumarin molecule acts as an electron acceptor at the SWCNT -coumarin complex. Variations of density and dipole moment values of coumarin after interaction were studied. Also, the frontier orbital energies, HOMO-LUMO gap, chemical hardness (η), electrophilicity index (ω), charge transferred (ΔNmax) and chemical potential (μ) were computed.  Pure coumarin is less conductive and smoother than SWCNT -coumarin. Our results show efficient coumarin loading with the interaction energy of -1.19 eV. NBO analysis shows that the occupied orbitals in the coumarin and the unoccupied orbitals in the nanotube overlap.