Aromaticity of Carbon Nanotubes

Abstract

Carbon nanotubes (CNTs) are aromatic, peri-condensed benzenoids, composed of sp 2 carbon atoms; the carbons are arranged in a graphite-like, hexagonal pattern. The aromatic character of armchair and zigzag nanotubes was compared with the corresponding rectangular graphite sheets, from which CNTs may be derived. The number of Kekulé structures in (2,2) m and (4,0) m CNTs and in planar rectangular graphite sheets of equivalent size, where m denotes the number of strips making up the CNTs (1 ≤ m ≤ 5), was determined. The aromatic character of the structures was estimated by using the Swinborne-Sheldrake equation. It was found that (2,2) CNTs are more aromatic than their planar counterparts and (4,0) CNTs. (4,0) CNTs are less aromatic compared to the corresponding planar structures. Hence it is more difficult to saturate (and functionalize) armchair CNTs than the corresponding planar graphite structures and zigzag CNTs.Keywords conjugated systems benzenoids functionalization Kekulé count CROATICA CHEMICA ACTA CCACAA 80 (2) 233¿237 (2007)

Magnetically Induced Ring-Current Strengths of Planar and Nonplanar Molecules: New Insights from the Pseudo-π Model

“…In the case of cylindrical CNTs, the magnetic response depends strongly on the structural parameters and the orientation of the external field with respect to the CNT. [69][70][71] When the external magnetic field is parallel to the CNT symmetry axis, the tube sustains (like [10]cyclophenacene) strong counter-rotating inner and outer ring currents. 16,86 When the external magnetic field is perpendicular to the CNT, the current density is diatropic inside and outside.…”

Molecular dynamics simulations of adsorption of long pyrene-PEG chains on athin carbon nanotube

“…CNTs are basically graphitic surfaces rolled up along different directions. The angle and direction of the rolling result in CNTs with surfaces having different aromaticity patterns decorated with a network of sp 2 carbon atoms [21][22][23][24]. This property secures numerous possibilities for the noncovalent functionalization of CNTs such as by using aromatic molecules [25] like pyrene.…”

Characterizing Functionalized Carbon Nanotubes for Improved Fabrication in Aqueous Solution Environments

“…In the context of electrophilic aromatic substitution (EAS) reactions, nitroso groups are known to be electron withdrawing, maleic anhydride groups are lightly electron releasing, and carboxylic acid groups are strongly electron releasing, which can be quantitatively described by Hammett sigma constants (σ). Since carbon nanotubes are essentially aromatic, peri-condensed benzenoids (composed of sp 2 carbons, arranged in a graphite-like hexagonal pattern) that have aromatic character (Linert et al, 2007;Lukovits et al, 2007) and are used to fabricate hierarchical structures (Zorbas et al, 2005), it is appropriate to explore how σ relates to our observed PZC measurements. Also known as the "substituent constant," σ determines the effect that a given substituent will have on the equilibrium and rate constants for the disassociation of benzoic acids.…”