AIM and NBO analyses on the interaction between SWCNT and cyclophosphamide as an anticancer drug: A density functional theory study

In this work, the molecular structures of single-walled carbon nanotube (SWCNT), cyclophosphamide and cyclophosphamide-SWCNT complex were optimized B3LYP/6-31G* level of theory. The nanotube used in this study was a (5,5) SWCNT including 150 C atoms. The NBO analysis showed that the transfer electron can be occurred from the lone pair of oxygen (donor atom) in the cyclophosphamide to the sigma* or pi* orbitals of the carbon atoms (acceptor atoms) in the SWCNT. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and energy gap (HOMO-LUMO) were calculated for the studied structures and the results indicated the stability of the complex. In addition, the calculated chemical shift isotropy (sigma) and the chemical shift anisotropy (Delta sigma) confirmed the interaction between cyclophosphamide and SWCNT. Also, the results of the atoms in molecule (AIM) theory indicated that the H-145-O-164 bond is a partial covalent bond.