1,3-Dipolar Cycloaddition in Stone-Wales Defective Carbon Nanotubes: A Computational Study

We have theoretically investigated the [2+3] cycloaddition reactions of 1,3 dipoles, azides (Na parts per thousand N+-NR-), with Stone-Wales (SW) defective (n, n) single-walled carbon nanotubes (SWCNTs), n = 4, 5, and 6. It is shown that topological defects such as the SW defects could drastically change the electronic structure and chemical reactivity of SWCNTs. Among the functionalized SW defective SWCNTs, the most stable configurations are obtained when the 1,3-dipoles are close to the heptagon-heptagon C=C bonds of SW defects. Therefore, azide derivatives Na parts per thousand N+-NR-, R= -H,-CH3,-NH2, -Ph, and -CN, are put close to the heptagon-heptagon C=C bonds of the SWCNTs. Negative values obtained for 1,3-dipolar cycloaddition reaction energies E-r indicate the exothermic character of [2+3] cycloaddition reactions. The results also indicate that the orientations of SW defects at the sidewalls of the SWCNTs (diagonal or parallel to the tube axis) play an important role in the reactivity of the C=C double bonds of SW defects. Substitution of an electron donating functional for hydrogen atom of azide leads to a decrease in the energy difference between the E (HOMO) of the dipole and the E (LUMO) of the dipolarophile, which facilitates interaction between the substrate (C=C bonds) and 1,3 dipoles.