Cyclodextrin mediated non-aqueous electrophoresis for chiral separations of anionic boron clusters

Anionic boron cluster compounds have recently made their way into many areas including medicinal chemistry and sensors due to favorable physical-chemical properties and their various biological activity. Notwithstanding the inherent chirality of these compounds, the exploration of the properties and activity of individual enantiomers remains uncharted territory. The permanent delocalized negative charge enables the electrophoretic mobility of these compounds. Thus, chiral electrophoresis, characterized by minimal consumption of chemicals and a sample, emerges as a promising candidate for a reliable quality control tool. The primary attempts in aqueous electrolytes showed some difficulties related to the limited solubility of these analytes. This study meticulously investigates the electrophoretic behavior and chiral separation of anionic [7,8-nido-C₂B₉H₁₁]^- and cobalt bis(dicarbollide)(1-) derivatives using a methanolic non-aqueous electrolyte with numerous derivatives of cyclodextrins. Randomly substituted hydroxypropyl-β-, methyl-β-, and hydroxypropyl-γ-cyclodextrins were identified as the most effective chiral selectors. The chiral separations delineated herein surpass previously published results in capillary electrophoresis in terms of resolution, peak shape, and the number of theoretical plates. Furthermore, the application of (2-hydroxy-3-N,N,N-trimethylamino)propylated β-cyclodextrin in non-aqueous environment resulted in the chiral separation of seven recently synthesized amino cobalt bis(dicarbollide)(1-) derivatives; thereby, reinforcing the extensive applicability of the developed methodology for different structural types of anionic cobalt bis(dicarbollides)(1-). These results qualify non-aqueous electrophoresis as a valuable tool for the enantiomeric purity control of anionic boron cluster compounds with respect to their further use in various areas.