Synthesis of Diaza-18-Crown-6-Functionalized ￥a-Cyclodextrin Derivatives at the Secondary Side and Induced Circular Dichroism Studies of Their Complexes with (2-Naphthoxy)alkylammonium Ions

摘要

β-Cyclodextrin derivatives connected with diaza-18-crown-6 through flexible bridges (R) at the secondary face 1a-c (1a: R = -(CH?)4-; 1b: R = -CH?CH?OCH?CH2-; 1c: R = -(CH?)8-) have been prepared. The association constants of 1 with (2-naphthoxy)alkylammonium ions (2a: alkyl = butyl; 2b: alkyl = octyl) were determined by induced circular dichroism (ICD) spectroscopy and it was found that the derivatization of β-CD with the diazacrown resulted in enhanced binding with 2, compared to the native β-CD. ICD Characteristics of the host-guest complexes indicate that a part of the alkylammonium moiety of 2 is protruded from the secondary side of the β-CD cavity, and the guest molecules 2a and 2b move to the secondary and primary side, respectively, to make the binding of the ammonium group with the diaza-18-crown-6 moiety more feasible. The energy accompanied by the relocation of the guest molecules inside β-CD moiety is compensated by the interaction energy between the ammonium ion and diazacrown ether.