Exploiting ¹³C/¹⁴N solid-state NMR distance measurements to assign dihedral angles and locate neighboring molecules

Abstract

The RESPDOR NMR method rapidly provides multiple 13C/14N distance measurements in natural abundance solids. In this study, 13C/14N RESPDOR information is shown, for the first time, to provide accurate molecular conformation and to locate non-bonded neighboring molecules.

NMR crystallography of molecular organics

“…13 C, 15 N REDOR experiments on mixtures of labelled and unlabelled compounds were used to measure an intermolecular distance of < 4 Å, which was found to be compatible with a limited number of packing arrangements via molecular modelling studies. Recently C,N distances up to 3.3 Å have been measured via dipolar couplings between 13 C and 14 N at natural abundance [307], giving access to a small number of angles between internuclear vectors in a pair of complex molecules. Such experiments have the advantage of not requiring labelling, with the drawback that dilution in unlabelled samples cannot be used to distinguish between inter-vs intra-molecular couplings [308].…”

Graphitic C2N3: An Allotrope of g-C3N4 Containing Active Azide Pentagons as Metal-Free Photocatalyst for Abundant H2 Bubble Evolution

“…The molecular structure of g -C 2 N 3 was further investigated by solid-state nuclear magnetic resonance (MAS NMR) of 13 C and 15 N (Figure f). In the 13 C spectrum, resonance peaks at chemical shifts of 154 and 162 ppm for g -C 2 N 3 are separately assigned to C(1) and C(2) atoms in the triazine unit, , while a characterized signal at 87 ppm that is not found in g -C 3 N 4 is identified as C(3) in aromatic azide pentagons . Accordingly, in the mutually corroborating 15 N profile, peaks at 153 and 124 ppm are ascribed to N(1) and N(2) of triazine hexagons, while signals at 224 and 106 ppm are features of N(3) and N(4) in the azide structure. , Consequently, the molecular structure of g -C 2 N 3 with aromatic azide pentagons is proposed and shown in Figure g.…”

Dihedral Angle Measurements for Structure Determination by Biomolecular Solid-State NMR Spectroscopy

“…Although not a focus of the current review, it is worth noting that many ssNMR distance measurements directly or indirectly constrain dihedral angles. In some cases, specific ssNMR experiments were designed with the explicit goal to determine dihedral angles via precise measurements of specific internuclear distances ( Sinha and Hong, 2003 ; Wi and Spano, 2011 ; Hu et al, 2012 ; Pope et al, 2018 ). This includes for instance the so-called BARE (Backbone Recoupling) experiments that measure the distances between backbone nitrogens and carbonyls, with implications for the intervening backbone torsion angles ( Hu et al, 2012 ).…”