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
Kk. Park et al., 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, B KOR CHEM, 21(11), 2000, pp. 1119-1124
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.