Conformational Self-Poisoning in Crystal Growth.

With the ever-increasing complexity of new drug compounds, their crystallization is becoming more challenging than ever. Controlling the crystallization of present and future drugs will remain a chimera unless we gain an improved understanding of the effects of molecular flexibility on crystal nucleation and growth at the molecular level. As a contribution to this understanding, we report here the growth kinetics of a series of diacids with chain lengths from 4 to 10 carbon atoms.

Nanoindentation of Molecular Crystals: Lessons Learned from Aspirin.

Nanoindentation enables the measurement of mechanical properties from single crystals with dimensions of a few micrometers. This experimental technique, however, has only recently been applied to molecular crystals. Key differences between the application of this technique to molecular crystals and metals and other inorganics are identified.

Concerning Elusive Crystal Forms: The Case of Paracetamol.

Increasing commercial application of state of the art crystal structure prediction to aid solid form discovery of new molecular entities allows the experimentalist to target the polymorphs with desired properties. Here we remind ourselves that in this field the gap between such prediction and experimentation can be vast, the latter depending strongly on kinetic processes not accounted for in the computations. Nowhere is this gap more evident than in examples of so-called "elusive" polymorphs, forms that have been found difficult to crystallize, sometimes taking years to appear or sometimes disappearing altogether.