Molecules in Strained Environment

Variable temperature (100—295 K) single-crystal X-ray diffraction study of the α-polymorph of glycylglycine and a glycylglycine hydrate

“…A comparative study of the effect of pressure on these systems is now in progress and will contribute to our understanding of the factors responsible for the different response of the same structure to the changes in temperature and changes in pressure. For some small-molecule crystals, including also the crystals of amino acids, a different response of the same structure to the two isotropic actions --decreasing temperature and increasing hydrostatic pressure --was reported and interpreted in terms of the different effect of temperature and pressure changes on different types of the intermolecular non-covalent interactions and on the conformations of molecules [2-5, 28, 31-33, 35-52], whereas for other systems the structural changes on cooling and with increasing pressure were similar [3,4,[38][39][40][41][42][43][44][52][53][54]. For example, the anisotropy of structural strain of g-polymorph of glycine on cooling and with increasing pressure was similar, whereas that of the a-polymorph is noticeably different [4,44].…”

Evaluation of the Microcrystallinity of a Drug Substance, Indomethacin, in a Pharmaceutical Model Tablet by Chemometric FT-Raman Spectroscopy

“…Then, 125 mg of the homogeneous powder mixture was compressed in a tabletting tester (Sankyo Paioteku Co., Japan) at various compressions (20,49,98,196 MPa). The tablets obtained were R-type, 7 mm in diameter and about 3 mm in thickness.…”

Variable-temperature and variable-pressure studies of small-molecule organic crystals

“…The flattening of the paracetamol molecules can be supposed to be interrelated with the compression of intermolecular hydrogen bonds, which manifests itself also in the IRspectra. 10,13,25 According to ab initio calculations, an individual paracetamol molecule should be flat (torsion angle equal to 0), 39 but in the real crystal structures the torsion angle is equal to about 21°-23° in the monoclinic polymorph 16,24 and to about 18° in the orthorhombic form. 15 This can be explained by the effect of intermolecular hydrogen bonds formation on the torsion angle: ab initio calculations have shown the value of the torsion angle in the molecule to be sensitive to the protonation of the OH-and NH-groups.…”