Self-assembly of perfunctionalized Beta-cyclodextrins and chiral discrimination by quartz crystal microbalance

Abstract

In this study, seven pairs of new QCM chiral sensors incorporated with self-assemblies of perfunctionalized beta-CDs coded as M-b-CD (M=Ph, MP, CP, BP, IP, MtP or MdP) were developed. Good chiral discrimination in the gas phase and liquid phase was achieved on the QCM sensors towards selected enantiomeric analytes (e.g. lactates, alcohols). Among the candidates, MP-b-CD arrays performed the best. In the gas phase, effective cooperative weak interactions, which depend on the molecular structures of the b-CDs and analytes (lock-and-key principle and extensive three-point rule), are mainly responsible for improved chiral discrimination. Generally, the liquid phase recognition process is subject to interplay of various factors (e.g. the shape and size of the host and guest molecules and the ability to form hydrogen bonds, pi-pi stacking and hydrophobic interactions) and a favorable conformational rearrangement leading to the most thermodynamically stable complex. This study offers a robust strategy to engineer a series of new chiral sensors applicable for real-time recognition and analysis of alcohols and lactates in the gas phase, and amino acids, alcohols and organic acids in the aqueous media.