DFT calculations of structures, ¹³C NMR chemical shifts, and Raman RBM mode of simple models of small‐diameter zigzag (4,0) carboxylated single‐walled carbon nanotubes

Abstract

Linearly conjugated benzene rings (acenes), belt-shaped molecules (cyclic acenes), and models of single-walled carbon nanotubes (SWCNTs) with one carboxylic group at the open end were fully optimized at the B3LYP/6-31G* level of theory. These models were selected to obtain some insight into the nuclear isotropic changes resulting from systematically increasing the basic building units of open-tip-monocarboxylated SWCNTs. In addition, the position of radial breathing mode (RBM), empirically correlated with the SWCNT diameter, was directly related with the radius of model cyclic acene rings. A regular convergence of selected structural, NMR, and Raman parameters with the molecular system size increase was observed, and a simple two-parameter mathematical formula enabled their estimation in infinity. The predicted (13) C NMR chemical shifts of carbon atoms close to the substituted rim of carboxylated models of zigzag (4,0) SWCNTs differed significantly from the pristine nanotubes.

Performance of revised STO(1M)‐3G basis set for prediction of 5‐fluorocytosine chemical shifts

“…It is well known that the predicted nuclear magnetic resonance (NMR) parameters are very sensitive to the level of theory and basis set flexibility and completeness . However, molecular modeling of large biomolecular structures and ordered carbon nanostructures has been a big challenge for the theory due to the system size leading to nonlinear increase of calculation time and lowering their predictive accuracy . In 2012, Voronkov et al modified small STO‐3G basis sets for a very efficient ones with relatively small number of basis functions, allowing an efficient calculation of electronic structure and magnetic properties of the studied systems.…”

Computational1H and13C NMR in structural and stereochemical studies

“…Continuing to the more sophisticated derivatives of benzene, it should first be noted that computed 1 H NMR chemical shifts were used as a reliable theoretical instrument for the investigation of free and encapsulated fullerenes [206][207][208] together with related different nanotubes. [209][210][211][212][213] As an example, for the linear condensed benzene rings modeling single wall carbon nanotube, 1 H NMR chemical shifts varied noticeably on the molecular size, that is, on the number of linearly condensed benzene units. In particular, the elongation of the chain led to a significant deshielding of the inner-most proton, which was close to the middle of the structure (about 9.8 ppm for the infinitely large polyacenes).…”

“…Based on the numerous contributions from Kupka's group and colleagues, [206][207][208][210][211][212][213] computed 1 H and 13 C NMR chemical shifts may be used as reliable theoretical estimates for different aromatic compounds, nanotubes, and free and encapsulated fullerenes, as exemplified above. Scientific activity of Professor Teobald Kupka is briefly outlined below.…”

DFT studies on armchair (5, 5) SWCNT functionalization. Modification of selected structural and spectroscopic parameters upon two-atom molecule attachment

“…Benzene was used as the secondary reference better compensating the systematic errors [52,53]. The B3LYP/6-311G* calculated IR/Raman spectra of pristine SWCNT and the corresponding diatomic adducts were processed in GaussView [54].…”