Comparison of GIAO and CSGT for calculating ¹³C and ¹⁵N nuclear magnetic resonance chemical shifts of substituent neutral 5‐aminotetrazole and 5‐nitrotetrazole compounds

Abstract

The comparison of the gauge-including atomic orbital (GIAO) and the continuous set of gauge transformation methods for calculating nuclear magnetic chemical shifts (CSs) mainly at density functional levels of theory are presented. Isotropic (13) C and (15) N magnetic CS for 14 compounds of tetrazoles are reported. Compared with establishing a convenient and consistent protocol to be employed for confirming the experimental (13) C and (15) N NMR spectra of tetrazole compounds, different combinations of functionals and basis sets were considered. The most reliable results were obtained at GIAO/B3LYP/aug-cc-pVDZ with integral equation formulation for the polarizable continuum model (PCM), which has the smallest root mean square errors and can be used to calculate (13) C and (15) N NMR CS with a very high accuracy for tetrazoles. These results show that the accurately calculated (15) N NMR CS of tetrazoles could be used for the evaluation of the intrinsic relationship between structure and explosive properties.

15N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine

“…The use of a ‘standard’ approach, i.e. the GIAO‐B3LYP calculations on the B3LYP optimized geometries, results in the largest overall RMS (23.3 ppm) comparable with that of the GIAO–B3LYP/aug‐cc‐pVDZ calculations reported previously …”

“…To achieve this aim, we, at first, tested the performance of several theoretical approaches that could be used for a reliable assignment of signals in the 15 N NMR spectra of triazides 1–7 . Recently, density functional theory (DFT) methods have been used to predict 15 N CS of some organic molecules . The DFT calculations of 15 N CS for azido groups were reported to result in a root mean square (RMS) error of 24.5 ppm.…”

Nitramino‐ and Dinitromethyl‐Substituted 1,2,4‐Triazole Derivatives as High‐Performance Energetic Materials

“…The 15 N NMR spectra for 6 and 14 are shown in Figure . The signals are assigned based on comparison with compounds reported in the literature and additional theoretical calculations B3LYP/6–311+g(2d,p) with IEF‐PCM continuum solvation models of Gaussian 03 software as well as analysis of 1 H– 15 N heteronuclear multiple bond correlation (HMBC, Supporting Information). For 6 , the signal for the ammonium cation was observed at the highest field of δ =−360.7 ppm.…”

Insight and performance of LC‐DFT vs DFT in the NMR shielding and chemical shift calculations: Case of CHClCHCF3

“…Nuclear magnetic resonance spectroscopy (NMR) has become a powerful tool for obtaining information concerning the structure and dynamics of molecules. [ 1–37 ] In the field of molecular modeling, the assessment of the NMR shielding was addressed by Ramsey in the early 1950s. [ 5,9 ] Thereafter, it has been modernized by Stevens et al in 1963.…”

“…An adequate basis set is used for geometry optimization and another for better accuracy in NMR calculation. It is worth mentioning that, for NMR parameters, the gauge‐including atomic orbital (GIAO) [ 1,3,9,10,29,31,32 ] was used throughout the work. This method has become more popular for NMR calculations.…”