Addition of Carbenes to the Sidewalls of Single‐Walled Carbon Nanotubes

Abstract

The addition of carbenes CX(2) (X=H, Cl) to single-walled carbon nanotubes (SWNTs) was investigated by density functional theory and finite, hydrogen-terminated nanotube clusters or periodic boundary conditions in conjunction with basis sets of up to polarized triple-zeta quality. For armchair [(3,3) to (12,12)] and zigzag tubes [(3,0) to (18,0)], reaction of CH(2) with the C--C bond oriented along the tube axis (A) is less exothermic than with those C--C bonds having circumferential (C) orientation. This preference decreases monotonically with increasing tube diameter for armchair, but not for zigzag tubes; here, tubes with small band gaps have a very low preference for circumferential addition. Axial addition results in cyclopropane products, while circumferential addition produces "open" structures for both armchair and zigzag tubes. The barriers for addition of dichlorocarbene to a (5,5) SWNT, studied for a finite C(90)H(20) cluster, are higher than that for addition to C(60), in spite of similar diameters of the carbon materials. Whereas addition of CCl(2) to [60]fullerene proceeds in a concerted fashion, addition to a (5,5) armchair SWNT is predicted to occur stepwise and involve a diradicaloid intermediate according to B3LYP, PBE, and GVB-PP computations. Addition to C bonds of (5,5) armchair tubes resulting in the thermodynamically more stable insertion products is kinetically less favorable than that to A bonds yielding cyclopropane derivatives.

Cycloaddition Functionalizations to Preserve or Control the Conductance of Carbon Nanotubes

“…[15]) and localized basis calculations (1.4 eV, Ref. [16]). Second, we find that the C 1 -C 6 distance for this O configuration (d 16 in Fig.…”

“…[16]). Second, we find that the C 1 -C 6 distance for this O configuration (d 16 in Fig. 1(c)) is much larger than the usual C-C distance (1.54Å in diamond and 1.42Å in graphite), a clear indication that the sidewall bond is broken [15,16,17,18].…”

“…Several mechanisms, including photochemical, electrochemical, and thermal, could then direct interconversion between the two tautomeric forms. Photochemical and electrochemical interconversion rely on the fact that the energy levels of the frontier orbitals are affected by d 16 , depending on their symmetries and charge distri- butions (e.g., the bond weakens as a filled orbital that has bonding character along C 1 -C 6 is emptied) [32,36]. Both photochemical excitations or electrochemical reduction or oxidation can populate or depopulate those frontier orbitals that favor the open or closed form; as a result, they would modulate the bond distance, and ultimately the conductance.…”

A Density Functional Theory Study of Chemical Functionalization of Carbon Nanotubes; Toward Site Selective Functionalization

“…According to the B3LYP calculations, both mechanisms are competitive in energy. In addition, Bettinger also analyzed carbene reaction between CCl 2 and a finite-length nanotube, and found that a transition state for the reaction lies only a few kcal/mol above the dissociation limit toward the nanotube and CCl 2 (Bettinger, 2006). Following the previous experimental and theoretical studies, we recently performed extensive DFT calculations to elucidate the stability of 12 configurations of cycloaddition of diethylbutane-2,3-diyl to the outer surface of a nanotube (Yumura & Kertesz, 2009).…”

“…Let us first discuss the addition of carbene into the outer (Chen et al, 2004;Bettinger, 2004;Zhao et al, 2005;Bettinger, 2006;Zheng et al, 2006;Lee & Marzari, 2008) or inner surface of the (5,5) or (10,10) nanotube, whose optimized geometries are seen in Figures 2 and 3. As mentioned above, the divalent atom of carbene binds into a CC bond of sp 2 systems.…”