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Electrostatic Repulsion between Cucurbit[7]urils Can Be Overcome in [3]Pseudorotaxane without Adding Salts
journal contribution
posted on 2013-04-19, 00:00 authored by M. Pessêgo, J. A. Moreira, A. M.
Rosa da Costa, P. Corrochano, F. J. Poblete, L. Garcia-RioThe host–guest chemistry between
cucurbit[7]uril (CB7) and
a series of bolaform (Bn) surfactants with different
chain lengths, n = 12–22, was the target of
our study. [3]Pseudorotaxanes are formed when the alkyl chain of the
bolaform has more than 14 carbon atoms. In these cases, two CB7 molecules
can be accommodated between the two head groups of the bolaform without
addition of electrolytes to the medium. In the case of a bolaform
with 12 carbon atoms, the electrostatic repulsion between the carbonyl
groups of the CB7 molecules avoids the threading of a second CB7 molecule
yielding a mixed structure formed by a [2]pseudorotaxane and an external
host–guest complex. The assembly behavior was investigated
using NMR spectroscopy, isothermal titration calorimetry (ITC), and
kinetic measurements.