Effect of curvature on the activation energy of monomethylation of carbon belts: a DFT study

Abstract

Alkylation of the cylindrical part of single-walled carbon nanotubes (SWCNTs) can improve solubility and oriented aggregation. In this study, the activation energy of the monomethylation of carbon belt surfaces was investigated using density functional theory to clarify the effect of curvature on nucleophilic radical addition. The activation energy decreases with increasing curvature, and at k = 0.290 Å−1, it is approximately half (7.1 kcal·mol−1) of that of the monomethylation of flat graphene flakes. The curvature significantly affects the repulsive energy between the CH3 and carbon belt portions, as well as local deformation around the bonding site.

Theoretical study of the relationship between the electronic structure of carbon nanotube surface and its hydrogenation sites

“…9,10) Recently, we also investigated monomethylation on the surface of carbon belts [CB(n) s] through density functional theory (DFT) calculations. 11) Our results revealed that as the curvature of CB(n) increases, E act decreases owing to the increase in the structural distortion of reaction sites and strengthening of intermolecular interactions.…”

“…This is in good agreement with our previously reported results, in that the E act of radical addition decreases as the reaction site curvature increases. 11) The E act of the monohydrogenation of C 60 was low but negative (−0.02 kcal mol −1 ), and the reaction proceeded spontaneously. Similarly, the E act of monohydrogenation at the C 4 -C 6 sites of the CNT was close to zero.…”

“…To improve the reactivity of polyaromatic carbons, research has been focused on making sp 2 carbon sp 3 -like in character by surface distortion. [6][7][8][9][10][11] While CNTs are rigid and physically stable, owing to their surface curvature, the electronic configuration of their constituent carbon atoms is not purely sp 2 . Therefore, the same chemical reactions proceed on CNT surfaces as on the C 60 fullerene surface, which serves as a guideline for the development of synthetic methods.…”

“…The structure around site C n (n = 0-7), which is attacked by the hydrogen radical (H), is defined by three angles (red arcs in Fig. 1): 6,11,21) 360 .…”

“…Even the medium-sized basis set 6-311 G(d, p) could provide relatively good results. 6,11) A well-known method for evaluating the reactivity of radical addition is the difference in electron density of the reaction site by the atom-condensed Fukui function. 28) Although this method is simple and convenient, it does not accurately represent the reactivity of CNTs (Table SVI).…”