When Crystals Do Not Grow: The Growth Dead Zone

Abstract

The experimental observation that certain crystal faces do not grow, despite being in contact with supersaturated solution, is a widely reported phenomenon. This concept of a growth 'dead zone' has been known for many years but its origin remains an unresolved problem in crystal growth. Sometimes it seems to be an inherent feature of the solution growth process while at others it appears that an impurity is an essential element for its appearance. Here we review existing data and provide new experimental evidence to confirm the widespread existence of the dead zone across a range of molecular materials. Available crystal growth kinetics are confronted with mechanistic models. Examination of the packing arrangements of appropriate crystal faces suggests that this behavior is linked to molecular scale surface roughness.Supporting information for this article is given via a link at the end of the document. Entry for the Table of Contents FULL PAPERThe 'general' existence of the dead zone has been confirmed and it appears to be related to surface rugosity.

Concerning the selection of crystallization modifiers for non-hydrogen bonded systems: the case of benzophenone

“…The morphologies suggest that both additives only affect the width, however this is not the whole storywhile 4ABZP does indeed reduce only the width growth rate, 4MBZP reduces both length and width growth rates, giving rise to 'dead zones' in both directions at low supersaturations. 28 These observations are thus qualitatively consistent with the morphological observations of Fig. 5, but not with the expectation that the additives would affect the [200] selectively.…”

Crystallization Process Development for the Final Step of the Biocatalytic Synthesis of Islatravir: Comprehensive Crystal Engineering for a Low-Dose Drug

“…The supersaturation at the seed point is 1.26. Upon addition of 2% jet-milled seed, the solution concentration remains the same after 2 h. The system either appears to exhibit a crystal growth dead zone 11 at these conditions or has extremely slow desupersaturation kinetics at this supersaturation (∼1.26) and solvent composition (31 wt % water vs DMF). The system begins to desupersaturate 10% into the second water addition at a supersaturation of ∼1.38 and 34 wt % water versus DMF.…”

The Impact of Ionic Surfactants on the Crystallisation of Glycine Polymorphs

“…The kinetic data for γ-glycine growth and the impact of CTAB are seen in full in Figure 7b which shows not only the accelerating impact of the surfactant on the growth but also the reduction in the extent of the growth dead-zone. [26] Overall, it is clear that at a given supersaturation and under quiescent conditions, α-glycine grows much faster than γglycine from pure solutions whereas this trend is reversed in the presence of CTAB. The magnitude of these effects is evidenced in Table 1 which provides the approximate volume growth rates for both forms.…”