Isomeric [2]rotaxanes and unidirectional [2]pseudorotaxane composed of alpha-cyclodextrin and aliphatic chain-linked carbazole-viologen compounds.
[structure: see text] Capping the alpha-cyclodextrin (alpha-CD) complex of 1-(N-carbazole)-10-[4-(4-pyridinio)-1-pyridinio]decane with 3,5-dimethoxybenzyl bromide in DMF gives two isomeric [2]rotaxanes, 2a and 2b, while alpha-CD and 1-(N-carbazole)-10-[4-(1-methyl-4-pyridnino)-1-pyridinio]decane 3 in water form mostly a unidirectional [2]pseudorotaxane having the same alpha-CD orientation as 2b. Structures were elucidated from 1H NMR and circular dichroism spectra. The orientational specificity of alpha-CD in the 3/alpha-CD [2]pseudorotaxane is due to the slow dethreading rate of the 2b-type isomer.
Park
Joon Woo
JW
Department of Chemistry, Ewha Womans University, Seoul 120-750, Korea. jwpark@mm.ewha.ac.kr
Song
Hyun Jung
HJ