Probing into complexation and separation of chiral-at-uranium complex to chiral sulphur enantiomers R/S-ethiproles

Chiral pesticides R/S-ethiproles(R/S-EPLs) have different biotoxicity. Due to the difficulty in the separation of chiral sulphur enantiomers, it is of great significance to study the selective recognition and separation of chiral sulphur enantiomers R/S-ethiproles. Based on DFT method, we theoretically designed a novel asymmetrical ligand of 4-amino-6-(9-[5-hydroxy-1H-indol-6-yl]-4,7-dimethoxy-1,10-phenanthrolin-2-yl)-1H-indol-5-ol (AHPIL). Then we further constructed the chiral-at-uranium complex, namely, Uranyl-AHPIL, to recognize and separate the enantiomers R/S-EPLs. Various analyses, including electrostatic potential (ESP), molecular geometric structures, Mayer bond order (MBO), electron density difference diagram (EDDM), independent gradient model based on Hirschfield partition (IGMH), quantum theory of atoms in molecules (QTAIM), molecular orbitals, the extended transition state-natural orbitals for chemical valence (ETS-NOCV), hard-soft acid-base (HSAB), relaxed force constants (RFCs) and binding free energy, furthermore unravelled the selective complexation and chiral separation ability of Uranyl-AHPIL receptor to R/S-EPLs guests. The results all indicated that the novel ligand could coordinate with uranyl to form a stable chiral-at-uranium complex, which more inclined selectively to bind with R/S-EPLs through thiyl oxygen O-22, and its complexation ability to S-EPL was much greater than to R-EPL. In solvents water, acetone, dichloromethane, benzene, cyclohexane and in gas phase, the separation factors of Uranyl-AHPIL towards R/S-EPL were in range of 189-633, and the enantioselectivity coefficients were all above 99%. These results provide a theoretical guidance for the complexation and separation of chiral pesticides and at the same time offer a new reference for the design of actinide complexes.