Correlation of 1JCH spin–spin coupling constants and their solvent sensitivities

Effect of Hydrogen Bond Formation on the NMR Properties of Glycine–HCN Complexes

“…NMR spectra provide valuable information on the molecular structure due to the sensitivity of measured parameters to the changes in the conformation of a molecule and to the influence of the environment. The last few decades have witnessed an extraordinary progress on the development of theoretical and computational methods of NMR spectroscopy and its application on various types of molecular systems including hydrogen-bonded clusters, as is evident from the extensive literature existing on the topic. − In many cases these hydrogen bonded interactions between the molecules can produce large variations in the chemical and structural properties of the molecules. In the present work, we focus on the hydrogen-bonded glycine–HCN molecular clusters to elucidate the effect of hydrogen bond formation on NMR parameters of these molecules.…”

1JCH couplings in Group 14/IVA tetramethyls from the gas-phase NMR and DFT structural study: a search for the best computational protocol

“…7,[19][20][21] This exchange-correlation density functional has been one of the more successful tools for predicting different magnetic properties of organic systems. 1,18,[22][23][24][25] The threshold and convergence parameters were tightened in all geometry optimizations (carried out by taking advantage of the T d symmetry) and frequency calculations by specifying 'Int = UltraFine', 'SCF = VeryTight', and 'Opt = VeryTight' for numerical integration grids and convergence criteria in Gaussian; 16 the former two keywords were also used in subsequent single-point NMR predictions. Moreover, the five pure d-functions have been mainly applied (5D option), see also Table S1 (ESI †).…”

“…Indeed, there is good, R 2 = 0.9948, expected in view of ref. 24, quasi-linear correlation DJ CH = f [2(e À 1)/(2e + 1)] between the J data and the values of the relative permittivity (formerly called dielectric constant, e) of three normally liquid tetramethyls, 56 accounted via the reaction field function (Fig. S1, ESI †); unfortunately, the value of e for PbMe 4 is not available in the literature.…”

“…The above observation is also in line with the finding that the solvent induced change in the 1 J CH coupling in a given solvent depends on the J value itself. 24 The foregoing vapor-phase J 0 , CH s and related liquid/solution data were subsequently compared with the high-quality computational results on J CH s in all five species EMe 4 obtained for the first time. It is well-known that the Fermi-contact (FC) contribution to this type of J-couplings is a dominating term.…”

“…59 Thus, all J CH s in species EMe 4 were calculated with Gaussian 09 using the GIAO formalism coupled with B3LYP, as this DFT protocol was found suitable for many similar computations performed previously. 1,18,24 Generally, a locally dense basis sets (LDBS) method [10][11][12][13] was applied. However, in the geometry optimization step, this idea was employed in a manner opposite to that of the originally formulated one by Chesnut et al 10 i.e., the E atom was described by the large (locally dense) basis set for best reproducing the E-C bond distances.…”