Enantioseparation of 5,5'-Dibromo-2,2'-Dichloro-3-Selanyl-4,4'-Bipyridines on Polysaccharide-Based Chiral Stationary Phases: Exploring Chalcogen Bonds in Liquid-Phase Chromatography

The chalcogen bond (ChB) is a noncovalent interaction based on electrophilic features of regionsof electron charge density depletion (sigma-holes) located on bound atoms of group VI. The sigma-holesof sulfur and heavy chalcogen atoms (Se, Te) (donors) can interact through their positive electrostaticpotential (V) with nucleophilic partners such as lone pairs, pai-clouds, and anions (acceptors). In thelast few years, promising applications of ChBs in catalysis, crystal engineering, molecular biology,and supramolecular chemistry have been reported. Recently, we explored the high-performance liquidchromatography (HPLC) enantioseparation of fluorinated 3-arylthio-4,4'-bipyridines containingsulfur atoms as ChB donors. Following this study, herein we describe the comparative enantioseparationof three 5,5'-dibromo-2,2'-dichloro-3-selanyl-4,4'-bipyridines on polysaccharide-based chiralstationary phases (CSPs) aiming to understand function and potentialities of selenium sigma-holes inthe enantiodiscrimination process. The impact of the chalcogen substituent on enantioseparationwas explored by using sulfur and non-chalcogen derivatives as reference substances for comparison.Our investigation also focused on the function of the perfluorinated aromatic ring as a pai-hole donorrecognition site. Thermodynamic quantities associated with the enantioseparation were derivedfrom van't Hoff plots and local electron charge density of specific molecular regions of the interactingpartners were inspected in terms of calculated V. On this basis, by correlating theoretical data andexperimental results, the participation of ChBs and pai-hole bonds in the enantiodiscrimination processwas reasonably confirmed.