Host-guest complexation of ionic liquid with - and -cyclodextrins: a comparative study by H-1-NMR, C-13-NMR and COSY

摘要

The formation of host-guest inclusion complexes (ICs) by an ionic liquid (IL) 1-butyl-3-methylimidazolium octylsulphate [Bmim][OS] within - and -cyclodextrins (CDs) has been explored by H-1 NMR, C-13 NMR and 2D H-1-H-1 COSY methods. The mechanism of the CD-[Bmim][OS] host:guest complex formation is systematically presented. The structural effect and various types of interactions, such as, H-bonding, electrostatic force and hydrophobic interactions that are responsible for the inclusion of the IL [Bmim][OS] into the cavity of CDs have been critically discussed with the help of NMR methods. It is observed that the hydrophobic effect plays a crucial role in supporting the formation of CD-[Bmim][OS] ICs. Furthermore, the spectral results obtained from 2D H-1-H-1 COSY NMR suggest that both H-bonding and electrostatic interactions also make a significant contribution to the stability of the IL-CD ICs.