Figure 4: The primary addition of one PP radical onto a SWNT model.
(a) Schematic image. The purple dot denotes an unpaired electron. (b) Energies of the different configurations possible for the primary attachment of a single PP radical on the SWNT models with various chiral indices estimated via the DFT calculations at the RB97D/3-21G* level. The calculated chiral indices were selected based on the chiral composition estimated based on the absorption spectrum shown in Supplementary Fig. 8. The calculation was also conducted using a (10,2)SWNT model but did not converge. The binding energy of the first PP radical was determined according to Ead=E(PP/(m,n)SWNT)–E((m,n)SWNT)–E(PP). The condensed SWNTs in Py-1-SWNT relative to p-SWNT [(8,3), (7,5), and (9,4)SWNTs (Supplementary Figs 8 and 9)] exhibit relatively large |Ead| values. The aryl addition and purification processes enriched these SWNTs because less reactive SWNTs were less dispersible in the organic solvents and were therefore removed during centrifugation. However, although the percentage of metallic SWNTs in the p-SWNT is low (<5%) and the |Ead| for (6,6)SWNT is not large, the kinetically high reactivity13 might enrich the metallic SWNTs after the reaction and purification processes.
