Determination of crystal structures and tautomeric states of 2-ammoniobenzenesulfonates by laboratory X-ray powder diffraction

Abstract

The crystal structures of 4-chloro-5-methyl-2-ammoniobenzenesulfonate and of the corresponding derivatives 4,5-dimethyl-and 4,5-dichloro-2-ammoniobenzenesulfonates have been determined from laboratory X-ray powder diffraction data. The tautomeric state of all three compounds could also be unequivocally determined from laboratory data, using careful Rietveld refinements. The tautomeric state was confirmed by IR spectroscopy. The compounds are neither isostructural to each other nor to the 5-chloro-4-methyl derivate, despite the similar size of the chloro and methyl substituents. The influence of the chloro and methyl substituents on the packing and on the thermal stability is demonstrated. All crystal structures were confirmed by dispersion-corrected DFT calculations. For the 4-chloro-5-methyl and the 4,5-dichloro derivatives the DFT calculations indicated that the observed polymorph should not be the thermodynamical one. However, no other polymorphs could be found in experimental polymorph screening, even using seeding with the corresponding isostructural phases. Obviously the DFT methods need further improvements.

New Polymorph of Dehydroepiandrosterone Obtained via Cryomodification

“…The use of dispersion-corrected periodic DFT calculations for verification and completion of the molecular crystal structures determined from powder data has become increasingly popular in recent years. These calculations were applied in structure determination of the 1:1 cocrystal of indomethacin and nicotinamide, monomethyl alkanes (C 26 –C 32 ), 2-ammoniobenzenesulfonates, 1:1 cocrystal of theophylline and 4-aminobenzoic acid, and Pigment Yellow 181 dimethyl sulfoxide N -methyl-2-pyrrolidone (1:1:1) solvate, among many others. Van de Streek and Neumann have systematically compared structures obtained from single-crystal and powder diffraction studies to the results of DFT-D optimizations.…”

Solid‐State NMR‐Driven Crystal Structure Prediction of Molecular Crystals: The Case of Mebendazole

“…In principle, it is also possible to determine the tautomeric state by careful Rietveld refinement. [51][52][53] However, the limited crystallinity of phase B (especially the broad reflection widths above 30°in 2Theta) did not allow its tautomeric state to be determined from powder data. In contrast, the SSNMR measurements positively showed the presence of tautomer 3.…”