DFT‐GIAO calculations of ¹⁹F NMR chemical shifts for perfluoro compounds

Abstract

The (19)F NMR shieldings for 53 kinds of perfluoro compounds were calculated by the B3LYP-GIAO method using the 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p), 6-311++G(d,p), 6-311G(2d,2p), 6-311++G(2d,2p), 6-311++G(2df,2p), 6-311++G(3d,2p), and 6-311++G(3df,2p) basis sets. The diffuse functions markedly reduce the difference between the calculated and experimental chemical shifts. The calculations using the 6-31++G(d,p) basis set give the chemical shifts within 10 ppm deviations from experimental values except for the fluorine nuclei attached to an oxygen atom, a four- and a six-coordinated sulfur atom, and FC(CF(3))(2) attached to a sulfur atom.

Enantiotropically-related polymorphs of {4-(4-chloro-3-fluorophenyl)-2-[4-(methyloxy)phenyl]-1,3-thiazol-5-yl} acetic acid: Crystal structures and multinuclear solid-state NMR

“…A more quantitative approach to understanding this effect was attempted using NMR chemical shielding calculations on clusters, but the achievable accuracy of these efforts was hampered by the minor nature of the effect, the small chemical shift range of 1 H nuclei, and the known difficulties in predicting 19 F shifts to an accuracy of within 10 ppm. 66 It is notable that no effects of p-stacking are observed in the 13 This trend is reflected in the crystal structures, which for example show an O2-O3 distance (across the dimeric carboxylic acid linkage) of 2.618 Å for Form 2 versus an average distance in Form 1 of 2.660 Å . The C11 carbonyl also acts as an acceptor for a weak interaction from Cl1 in both polymorphs; however, this interaction is not much different in Form 2 (3.263 Å ) than in Form 1 (3.187-3.393 Å ), suggesting that it does not contribute to the 1 H and 13 C shielding effects.…”

“…66 Because of this, the results of B3LYP/ 6-311 þ G(2d,p) GIAO 19 F predicted chemical shielding were not expected to offer much insight into the quality of the final Form 2 structure, and larger basis sets were not able to improve the results. Gas-phase B3LYP/6-311 þ G(2d,p) calculations on Form 1 molecules A and B predicted their 19 F resonances to be 7.4 and 11.8 ppm more shielded than the Form 2 resonance, which does not agree with the shielding trend in Figure 9.…”

Theoretical investigation on multinuclear NMR chemical shifts of some tris(trifluoromethyl)boron complexes

“…According to previous studies, diffuse function is important for 19 F chemical shift calculation that can markedly reduce the difference between the calculated and experimental chemical shifts. [19,30,33] Therefore, 6-31+G(d,p) was used in chemical shift calculations based on 6-31G * geometries. For 6-311+G(d,p) geometries, the same basis set (6-311+G(d,p)) was used in NMR calculations.…”

“…First, we consider the 11 The relationship between the theoretical and experimental chemical shifts can be seen easily from the linear fitting of the theoretical dataset to the experimental one. [19,29,33,35] The linear regression equations for the four sets of calculated chemical shifts can be expressed as…”

A computational study of some electric and magnetic properties of gaseous BF3 and BCl3

“…For example, difficulties in calculating the magnetic properties of fluorine containing molecules are well known. [32][33][34][35][36] Ruud et al have demonstrated that the additivity of magnetizabilities ͑known as Pascal's rule͒ breaks down for fluorine-containing species. 34,35 For calculations to match the accuracy of the experiment, extensive basis sets are required.…”