Probing intermolecular interactions in a diethylcarbamazine citrate salt by fast MAS 1 H solid-state NMR spectroscopy and GIPAW calculations

Abstract

Fast magic-angle spinning (MAS) NMR is used to probe intermolecular interactions in a diethylcarbamazine salt, that is widely used as a treatment against adult worms of Wuchereria bancrofti which cause a common disease in tropical countries named filariasis. Specifically, a dihydrogen citrate salt that has improved thermal stability and solubility as compared to the free form is studied. One-dimensional H,C and N and two-dimensionalH-C and N-H heteronuclear correlation NMR experiments under moderate and fast MAS together with GIPAW (CASTEP) calculations enable the assignment of the H,C and N/N resonances. A two-dimensional H-H double-quantum (DQ) -single-quantum (SQ) MAS spectrum recorded with BaBa recoupling at 60kHz MAS identifies specific proton-proton proximities associated with citrate-citrate and citrate-diethylcarbamazine intermolecular interactions.

An XRD and NMR crystallographic investigation of the structure of 2,6-lutidinium hydrogen fumarate

“…The resulting y-intercept was taken as σ ref . 40,41 A literature value was used for 14 N. 42 It is noted that it is common practice to calculate a specific reference shielding for each system 43 (see, e.g., Table S8 of ref. 43), though average values over a range of compounds are also available.…”

Characterization of H2‐Splitting Products of Frustrated Lewis Pairs: Benefit of Fast Magic‐Angle Spinning

“…The observation of two HP resonances agrees with the single‐crystal structure in which two crystallographically distinct monomers of compound 1 were found in the asymmetric unit and explains the deviations from the solution‐state chemical‐shift values for which only one species is detected (see Figure a for the solution‐state spectrum). This illustrates the potential of MAS experiments >100 kHz particularly in NMR crystallographic approaches ,,…”

“…This illustrates the potential of MAS experiments > 100 kHz particularly in NMR crystallographic approaches. [8,32,33] We have used the 2D SD spectrum to extract a 1D spectrum along the direct dimension at 1.1 ppm. This trace is given in Figure 2e and shows the highest resolution observed in this work, since it is less influenced by sample inhomogeneities manifested as chemical-shift distributions in the NMR spectrum (vide infra) and all residual background and/or water resonances are absent.…”

5‐amino‐2‐methylpyridinium hydrogen fumarate: An XRD and NMR crystallography analysis

“…As each individual molecule carried a charge, this was specified in the .param file. [35] The [36,37] A literature value of −153 ppm was used for 14 N. [38] It is noted that it is common practice to calculate a specific reference shielding for each system [39], though average values over a range of compounds are also available. [40] By comparing the parameters in the full crystal structure with those for the isolated molecule, insight is provided into the intermolecular interactions responsible for maintaining the crystal structure.…”