# Nonclassical Crystallization of the L‑Tartrate Salt of Cyamemazine

## TL;DR

This paper explores how a specific salt of an antipsychotic drug forms crystals through a nontraditional process involving liquid crystalline intermediate phases.

## Contribution

The study reveals a nonclassical crystallization pathway involving liquid crystalline intermediates for cyamemazine L-tartrate.

## Key findings

- An intermediate droplet phase with liquid crystalline properties was observed during crystallization.
- The dense phase showed a fan-like texture and was analyzed using NMR, XRD, and SRS imaging.
- The crystallization process involves a transition from droplet to dense phase with distinct characteristics.

## Abstract

This study investigates
the nonclassical crystallization of cyamemazine L-tartrate,
a kryptoracemic salt of the antipsychotic drug cyamemazine.
The crystallization pathway was studied via slurry conversion of a
suspension of cyamemazine and L-tartaric acid in 2-propanol
to the salt. Notably, the system transitioned through an intermediate
droplet phase, which subsequently coalesced to form a dense phase.
Both intermediate phases exhibited liquid crystalline character when
observed under a polarized light microscope. The droplets demonstrated
birefringence and a distinct Maltese cross extinction pattern, confirming
their liquid crystalline nature. The dense phase revealed a fan-like
texture when isolated and examined between glass slides. Comprehensive
analyses of the intermediate droplet phase and the dense phase were
conducted using solution 1H nuclear magnetic resonance
(NMR), X-ray diffraction (XRD), and in situ stimulated Raman scattering
(SRS) imaging. The combination of imaging and analytical techniques
employed in this study allowed for elucidation of the nature and composition
of the intermediate phases involved in the crystallization process.