Preferential Enrichment: Classification of Crystal Structures by Graph Set Notation

Abstract

Preferential enrichment is a symmetry-breaking chiral separation phenomenon that is initiated by the solvent-assisted solid-to-solid transformation of the first-formed metastable polymorphic form into a thermodynamically stable one during crystallization from the supersaturated solution of certain kinds of racemic mixed crystals (i.e., solid solutions or pseudoracemates) composed of two enantiomers in organic solvents without the aid of any external chiral element. Here, we report the classification of the crystal structures by using graph set analysis based on the hydrogen-bonding motifs. Using graph sets, we have observed interesting relationship between the occurrence of preferential enrichment and the crystal structures.