Structure–property correlations in piracetam polytypes

Abstract

Analysis of piracetam polytypes using energy-vector models, thermal expansion and nanoindentation measurements, produces a plausible link between their crystal structures and tableting behaviour.

Mechanical anisotropy and tabletability of famotidine polymorphs

“…For example, we have used such models to discuss the properties of piroxicam 46 and piracetam. 47 The models comprise lines linking the centroids of molecules, scaled in length according to the magnitude of the interaction energy between the linked molecules. The most stabilizing interaction in the structure is displayed as a complete line, and less stabilizing interactions are scaled proportionally to produce gaps in the lines.…”

Polytypism and Packing-Dependent Colossal Positive and Negative Thermal Expansion in a 2D Layered Cerium-Based Coordination Polymer

“…Namely, flexible ethyl groups in propionate anions are able to rotate, which leads to unusual lattice dynamics and phase transitions. ,− Regarding the layered rare-earth propionates, one could expect a highly anisotropic thermal expansion with large positive and negative linear coefficients of thermal expansion (CTEs) that could be useful for the development of high-precision thermal actuators. − Indeed, many anisotropic coordination polymers are known to exhibit anomalous (anisotropic or/and negative) thermal expansion; − on the other hand, there are reports on colossal negative thermal expansion (NTE) promoted by the rotation or/and reorientation of certain structural units. − In particular, a combination of both factors gave rise to NTE for 1D-polymeric rare-earth pivalates where the negative α CTE of −128 MK –1 was reached . Furthermore, in general, CTEs are additionally packing-dependent. , Therefore, the studies of RE propionate polytypes and their thermal expansion represent significant interest.…”

“…52 Furthermore, in general, CTEs are additionally packing-dependent. 34,53 Therefore, the studies of RE propionate polytypes and their thermal expansion represent significant interest.…”

Active control of molecular stacking types in a congeneric library of dihalogenated salicylideneaniline crystals and their solid solutions

“…9 Moreover, Bond et al performed nanoindentation experiments and demonstrated the effect of polytypism on the mechanical properties of pharmaceutical drugs. 7,10,11…”

“…9 Moreover, Bond et al performed nanoindentation experiments and demonstrated the effect of polytypism on the mechanical properties of pharmaceutical drugs. 7,10,11 Halogen-halogen interactions are moderately strong and bimodally directional, denoted as type I and type II interhalogen contacts, respectively. 12,13 These interactions aid the fabrication of the desired supramolecular structures and provide unique properties to the organic crystals, such as elasticity, plasticity, 14 and stimuli responsiveness.…”