Rotaxanes based on the 1,2-bis(pyridinio)ethane-24-Crown-8 templating motif

摘要

The supramolecular interaction between 1,2-bis(pyridinio)ethane axles and 24-membered crown ether wheels provides a template for the formation of interpenetrated [2]pseudorotaxanes. The preformed [2]pseudorotaxanes can then be kinetically trapped to produce permanently interlocked [2]rotaxanes by stoppering with bulky groups that prevent the unthreading of the resulting dumbbell from the wheel. Six [2]rotaxanes were created using 24-crown-8 (24C8), dibenzo-24-crown-8 (DB24C8) and dinaphtho-24-crown-8 (DN24C8) as the wheel and two methods of stoppering; alkylation of a terminal pyridine with tert-butylbenzyl groups and esterification of a terminal benzyl alcohol with p-(tert-butyl)benzoate groups. The [2]rotaxanes were characterized by 1H NMR spectroscopy, electro-spray mass spectrometry and X-ray crystallography.