Spectroscopic characterizations and sum-frequency generation of chiral binaphthol derivatives

Abstract

Research concerning the enantiomers of chiral active compounds and especially their separations constituted a major challenge for drugs design. It is crucial to study the chirality of molecules for their applications. This study aims to investigate chirality in liquid media containing enantiopure chiral molecules from derivatives of binaphthol through sum- frequency generation microscopy and spectroscopic techniques. Derivatives of binaphthol, obtained by substituting the hydrogen atoms of hydroxyl group (-OH) with alkyl groups:     (-CH₃) and (-C₂₂H₄₅), were studied using UV visible spectroscopy, NMR, IR transmission, Raman and sum-frequency generation microscopy (SFG). Modifications of chemical bonds which took place on the molecule of binaphthol were performed and highlighted by IR and Raman measurements. On IR and Raman spectra, bands related to (-OH) group vibrations (1382 cm^-1, 3429 cm^-1 and 3507 cm^-1) disappeared while bands corresponding to alkyl chains vibration modes appeared (708 cm^-1, 2848 cm^-1 and 2915 cm^-1). Chiral SFG spectra and images were then performed on the functionalized R Binol-C₂₂ sample. Good contrasts were obtained in appropriate configurations of the sum-frequency generator device. Chiral compounds R Binol-C₂₂ were detected using Sum-frequency generation imaging and spectroscopy. The information obtained by sum-frequency generation is of great importance to the community.