How To Control Recognition: From Brucinium Double Salts to Racemic Resolution

• Published in: Crystal growth & design 2019-08, Vol.19 (8), p.4632-4640
• Main Authors: Ganczar, Emilia, Białońska, Agata, Ciunik, Zbigniew
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.9b00520

Studying the mechanisms of racemic resolution of the model compound N-(3-nitrobenzoyl)­aspartic acid by formation and fractional crystallization of brucinium diastereomeric salts, we found that depending on the environment (solvents) the recognition leads to effective or ineffective racemic resolution. During successful racemic resolution, bis­(brucinium)-N-(3-nitrobenzoyl)-l-aspartate hydrate methanol solvate precipitates as the first fraction. In turn, double salts and solid solution are formed in the fruitless racemic resolution. Formation of the double salt results from recognition of centrosymmetric anionic dimers on the common brucinium corrugated layer. The common brucinium corrugated layer together with its solvation sphere participates in recognition of the anions, leading to formation of the solid solution. Changing the solvent system according to its dielectric constant, more dispersive or more directional interactions gain importance. The racemic resolution and formation of bis­(brucinium)-N-(3-nitrobenzoyl)-l-aspartate hydrate methanol solvate are related to three-point recognition of the anions by brucinium self-assembly.