Adsorption of free-base phthalocyanine on Stone-Wales defect-containing carbon nanotubes: A DFT study

The present study addresses the influence of topological defects incorporated into sidewalls of single-walled carbon nanotubes (SWNTs) on the strength of noncovalent bonding and the state of adsorbed complex organic molecules. The interaction of free-base phthalocyanine (H2Pc) with Stone-Wales (SW) defect-containing armchair and zigzag nanotube models (ANT and ZNT, respectively) was studied at the PBE-D/DNP and M06-2X/6-31G(d,p) theoretical levels. The results obtained were analyzed by comparing them with those for DFT calculations on similar defect-free nanotube systems, with a particular emphasis on the data accounting for basis set superposition error (BSSE). As a whole, free-base H2Pc adsorbs on SW defect-containing SWNT models stronger than on the parent defect-free nanotubes. In PBE-D calculations, the increase in binding strength varies between 2.01 and 6.31 kcal/mol (0.087 and 0.274 eV), depending on SWNT chirality and defect orientation. In BSSE-corrected M06-2X calculations, this effect is less evident. C(H2Pc)...C(SWNT) are usually the shortest separations, followed by N(H2Pc)...C(SWNT) and H(H2Pc)...C(SWNT). Frontier orbital-related characteristics obtained exhibit insignificant differences as compared to similar systems based on defect-free ANT and ZNT models. For most systems, for both computational techniques HOMO-LUMO gap energies change by less than 0.06 eV. The pattern of HOMO-LUMO orbital distribution was found to be broadly variable.