Synthesis of diaza-18-crown-6-functionalized beta-cyclodextrin derivativesat the secondary side and induced circular dichroism studies of their complexes with (2-naphthoxy)alkylammonium ions

beta -Cyclodextrin derivatives connected with diaza-18-crown-6 through flex ible bridges (R) at the secondary face 1a-c (1a: R = -(CH2)(4)-; 1b: R = -C H2CH2OH2CH2-; 1c: R = -(CH2)(8)-) have been prepared. The association const ants of 1 with (2-naphthoxy)alkylammonium ions (2a: alkyl = butyl; 2b: alky l = octyl) were determined by induced circular dichroism (ICD) spectroscopy and it was found that the derivatization of beta CD with the diazacrown re sulted in enhanced binding with 2, compared to the native beta -CD. ICD Cha racteristics of the host-guest complexes indicate that a part of the alkyla mmonium moiety of 2 is protruded from the secondary side of the beta -CD ca vity, and the guest molecules 2a and 2b move to the secondary and primary s ide, 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 beta -CD moiety is compensated by the interac tion energy between the ammonium ion and diazacrown ether.