Co-Crystallization Kinetics of 2:1 Benzoic Acid–Sodium Benzoate Co-Crystal: The Effect of Templating Molecules in a Solution

Abstract

The addition of dissolved templating molecules in crystallization will create “supramolecular assemblies” within the solution, serving as “anchor points” for the solute molecules to nucleate and grow. In this work, nucleation and crystal growth kinetics of 2:1 benzoic acid (HBz)–sodium benzoate (NaBz) co-crystallization with or without templates in a solution were analyzed by monitoring the concentration of the mother liquor during cooling crystallization. The results showed that the addition of the dissolved 2:1 or 1:1 HBz–NaBz co-crystals as templating molecules could reduce the critical free energy barrier of 2:1 HBz–NaBz co-crystal during its nucleation, but did not significantly affect the order of crystal growth rate. On the other hand, the critical free energy barrier of the nucleation process was increased if dissolved NaBz was used as a templating molecule, while a significant rise in the order of crystal growth rate occurred. The crystal habit obtained from the NaBz-templated system was needle-like, suggesting that sodium–sodium coordination chains of NaBz supramolecular assemblies in the solution phase were responsible for creating elongated crystals. Conversely, a large prismatic crystal habit found in non-templated and 2:1 and 1:1 HBz–NaBz co-crystal-templated systems implied that those templating molecules formed sparsely interconnected supramolecular assemblies in the solution phase.

Chemistry and Modern Techniques of Characterization of Co-Crystals

“…The technique was systematized by the ternary stage illustration and demonstrated a resilient functioning series for the co-crystal development and validated the predictable connection in induction period and supersaturation. Nicotinamide:carbamazepine co-crystal production was also implemented by the reaction co-crystallization using open-air conditions [17].…”

Transformation of amorphous calcium phosphate to monoclinic nano-hydroxylapatite

“…Alternatively, beam reflectance, turbidity, and crystal concentration measurements were adopted in the induction time confirmation of crystal growth. 10 Meanwhile, the transformation can be quantitatively tracked through a crystallinity index (CI) extracted from Raman spectra, i.e., full width at half maximum (FWHM) of Raman peak, 11,12 as CI Raman is less influenced by the carbonate content than the CI FT-IR , and more direct and rapid than CI XRD of moist samples. 12,13 In addition, impurity ions, i.e., metallic, anionic, and organic ions, 14,15 can inhibit or stimulate ACP crystallisation through lattice incorporation or surface adsorption.…”