Measuring multiple¹⁷O–¹³CJ-couplings in naphthalaldehydic acid: a combined solid state NMR and density functional theory approach

Abstract

A combined multinuclear solid-state NMR and a density functional theory computational approach, with SIMPSON simulations, is evaluated to determine the four heteronuclear 1J(13C,17O) couplings in naphthalaldehydic acid.

Mapping of N−C Bond Formation from a Series of Crystalline Peri‐Substituted Naphthalenes by Charge Density and Solid‐State NMR Methodologies

“…A mechanism for measuring the 1 J coupling in the solid‐state is to utilise the spin‐echo sequence which refocuses the evolution of all the terms that appear as offsets, in particular those that are caused by a distribution of chemical shifts. The use of spin echoes in an NMR experiment allows the detection of chemical shift separated J couplings even when inhomogeneous broadening means it is not directly visible in the observed spectrum [29] . The presence of other highly coupled nuclei with large quadrupolar couplings (such as 14 N or 17 O) can also cause dephasing of the signal and prevent accurate measurements of the J ‐coupling, therefore the measurement was observed from the perspective of the 15 N nuclei which is solely coupled to 99 % 13 C ( I = ), whereas the more sensitive 13 C is coupled to 60 % 15 N ( I = ) and 40 % quadrupolar 14 N ( I =1), which would cause greater dephasing and overestimation of the 1 J coupling.…”

“…We have previously discussed a methodology of utilizing periodic DFT calculations on molecular structures determined by single‐crystal X‐ray crystallography to determine 1 J couplings which are validated with spin‐echo solid‐state NMR experiments. Here, we expand this methodology to compare the charge density maps with NMR observations [29] …”

“…The use of spin echoes in an NMR experiment allows the detection of chemical shift separated J couplings even when inhomogeneous broadening means it is not directly visible in the observed spectrum. [29] The presence of other highly coupled nuclei with large quadrupolar couplings (such as 14 N or 17 O) can also cause dephasing of the signal and prevent accurate measurements of the J ‐coupling, therefore the measurement was observed from the perspective of the 15 N nuclei which is solely coupled to 99 % 13 C ( I = ), whereas the more sensitive 13 C is coupled to 60 % 15 N ( I = ) and 40 % quadrupolar 14 N ( I =1), which would cause greater dephasing and overestimation of the 1 J coupling. We have previously discussed a methodology of utilizing periodic DFT calculations on molecular structures determined by single‐crystal X‐ray crystallography to determine 1 J couplings which are validated with spin‐echo solid‐state NMR experiments.…”

Solid-state 17O NMR study of α-d-glucose: exploring new frontiers in isotopic labeling, sensitivity enhancement, and NMR crystallography

“…The interplay between the two NMR tensors is responsible for the observed field dependence of the static 17 O NMR spectra. From an analysis of these static powder line shapes, we were able to obtain the principal components of the 17 O CS tensor and their relative orientations with respect to the 17 glucosamine, 26 and several other related functional groups such as hemiacetal/hemiketal, 51,52 gem-diol, 53 hydroxyl, 54 and phenolic groups. [55][56][57] Because the six oxygen-containing functional groups in α-D-glucose are very similar, their 17 O isotropic chemical shifts, δ iso ( 17 O), are found within a small range of 60 ppm.…”

Mapping of N−C Bond Formation from a Series of Crystalline Peri‐Substituted Naphthalenes by Charge Density and Solid‐State NMR Methodologies

“…[28] Amechanism for measuring the 1 J coupling in the solid-state is to utilise the spin-echo sequence which refocuses the evolution of all the terms that appear as offsets,inparticular those that are caused by adistribution of chemical shifts.T he use of spin echoes in an NMR experiment allows the detection of chemical shift separated J couplings even when inhomogeneous broadening means it is not directly visible in the observed spectrum. [29] Thep resence of other highly coupled nuclei with large quadrupolar couplings (such as 14 No r 17 O) can also cause dephasing of the signal and prevent accurate measurements of the J-coupling,t herefore the measurement was observed from the perspective of the 15 Nnuclei which is solely coupled to 99 % 13 C(I = 1 = 2 ), whereas the more sensitive 13 Ciscoupled to 60 % 15 N( I = 1 = 2 )a nd 40 %q uadrupolar 14 N( I = 1), which would cause greater dephasing and overestimation of the 1 J coupling.W eh ave previously discussed am ethodology of utilizing periodic DFT calculations on molecular structures determined by single-crystal X-ray crystallography to determine 1 J couplings which are validated with spin-echo solidstate NMR experiments.H ere,w ee xpand this methodology to compare the charge density maps with NMR observations. [29] Theh eteronuclear 15 N- 13 Cs pin-echo decay for the aldehyde 2 and dinitrile 3 (Figure 2a and b) both show very shallow exponential decays which are indicative of narrow resonances that are not broadened by 1 J NC coupling contributions.Agreen simulated fit is given for the T 2 decays,with the blue SIMPSON [30] simulation of the periodic DFT determined 1 J NC coupling,a nd their product is given in red.…”