Quantum mechanical study of carbon nanotubes functionalized with drugs, pentoxifylline and lysofylline

The noncovalent interactions of drug pentoxifylline (PTX) with (5, 5) pristine and COOH functionalized-carbon nanotube and the mechanisms of covalent functionalization of the drug, lisofylline (LSF) with (5, 5) COOH and COOCl functionalized carbon nanotube have been studied by density functional theory calculations. Quantum molecular descriptors for four configurations of noncovalent interaction are calculated. It is found that binding of PTX with COOH functionalized CNT is thermodynamically favorable. COOH and COCl functionalized CNT can bind to lysofylline via OH (COOH mechanism) and Cl (COCl mechanism) groups, respectively. The bather energies of two mechanisms have been evaluated and compared with each other. It was found that the COOH mechanism has activation energy higher than the COCl mechanism, and hence the reason for suitability of COCl pathway for covalent functionalization.