The recently discovered technique of deracemization by means of grinding a racemic conglomerate in contact with a solution wherein racemization occurs has been scaled up using an industrial bead mill to demonstrate the practical applicability. The time needed to reach the enantiopure end state is drastically reduced as a result of the efficient grinding that can be achieved using bead mills.

The needle morphology of the commercial blue pigments copper phthalocyanine and metal-free phthalocyanine is studied using computer simulations and is compared with vapor grown crystals. Both phthalocyanines grow from the vapor at 700 K as very thin needles. The crystals are faceted along the needle axis, having one basal face and several side faces, and are not faceted at the top. The structures of the two phthalocyanines are similar and highly anisotropic leading to one preferred direction of growth. Conventional morphology methods fail to predict the correct morphology and aspect ratio of the needles. The morphology of the metal-free phthalocyanine crystals was simulated using the attachment energy method, kinetic Monte Carlo simulations, and a new morphology tool, STEPLIFT, based on a step energy approach. Kinetic Monte Carlo simulations give the most accurate representation of the experimental morphology, explaining also the variety of the observed side faces. STEPLIFT gives reasonable results in a much shorter time.

The extremely elongated growth spirals observed using atomic force microscopy on the largest {101̅} faces of the needle crystals of vapor-grown metal-free β-phthalocyanine are analyzed. An analytical model for the growth of anisotropic rectangular spirals is proposed to relate step distances and the step energies to the driving force for crystallization. The model is confronted with the experimental results, with kinetic Monte Carlo simulations, and with a growth step analysis. The model is well able to describe the observed and simulated spiral shapes. In addition, the experimental driving force for crystallization could be estimated and turns out to be reduced considerably as a result of diffusion limitation when compared to the value obtained for ideal gas behavior.

The unique behavior of the active pharmaceutical ingredient Venlafaxine free base, used as an antidepressant, with respect to polymorphism and chiral resolution is reported. Using several complementary techniques, three crystal structures of Venlafaxine were identified and isolated. All three structures are composed of virtually identical enantiomeric pure layers with different stacking modes. In the crystal structure with the highest melting point, the enantiomeric separation is complete, leading to a racemic conglomerate. The conglomerate can be grown from solution or via a solid–solid phase transition of the lowest melting racemic compound. Remarkably, the crystal shape is conserved during the transition. The corresponding chiral resolution is achieved via a local melting process, allowing for a long-range migration of the molecules between layers.

The overabundant occurrence of single-handed chiral molecules in living systems has inspired scientists for well more than a century. A route to the evolution of a single chiral solid phase, using abrasive grinding of the crystals in contact with a saturated solution, has been demonstrated for the achiral compound NaClO3(1) crystallizing in a chiral space group and, recently, for an intrinsically chiral amino acid derivative.(2) In order to obtain insight in the complex processes involved in these experiments, we developed a computer model that is based only on attrition and Ostwald ripening. We find that, besides the relative rates of attrition and Ostwald ripening, the racemization efficiency in the solution is an essential parameter in the deracemization process. For high efficiency the evolution to single chirality is stochastic, whereas for lower values the process becomes increasingly deterministic and the handedness of the single chiral solid end state is readily controllable. The results show excellent agreement with experimental data and allow a further optimization of this promising deracemization technique.

The crystal structure of several industrially important organic pigments namely C.I. Pigment Violet 23, C.I. Pigment Red 202 and C.I. Pigment Yellow 139 were predicted using the Cerius2 Polymorph Predictor in combination with XRPD patterns. After generation and energy minimisation of the candidate structures for each pigment, their calculated powder patterns were compared with those obtained experimentally using X-ray diffraction. The structures which best fitted the experimental powder patterns were regarded as possible structures of the compound; finally, a rigid body Rietveld refinement was performed to validate the choice of the structure. The structure of C.I. Pigment Violet 23 has not previously been published while the predicted structures of C.I. Pigment Red 202 and C.I. Pigment Yellow 139 were in accordance with the published structures. The work demonstrates that pigment crystal structure can be predicted using a low quality X-ray powder diffraction pattern.

The crystal growth of a monotropic polymorphic system of a yellow isoxazolone dye has been studied. One of the two metastable polymorphs grows into a needle-shaped morphology; the stable form is rhombic. The metastable third polymorph grows only from the melt and has a solid–solid phase transition to the needle-shaped form within hours at any temperature below the melting point. The polymorphic phase diagram has been determined for a wide range of concentrations in three solvents.