Regioselective Recognition of a [60]Fullerene-Bisadduct
by Cyclodextrin
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Abstract
The
three different regioisomers of bis-<i>N</i>-methylfulleropyrrolidines
have been separated by controlling the relative amounts of γ-cyclodextrin
and dimethyl sulfoxide (DMSO) contained in solutions of these compounds.
When a small amount of γ-CDx was used in a mechanochemical high-speed
vibration milling apparatus, the <i>trans-1</i> and <i>trans-2</i>•γ-CDx complexes were separated from
the <i>trans-3</i>•γ-CDx complex. In contrast, <i>trans-3</i> was extracted in a relatively high ratio with an
excess of γ-CDx. The addition of DMSO to aqueous solutions of
the fullerene derivative•γ-CDx complexes allowed for
the three regioisomers to be obtained in high purity (>95%). The
basis
for the observed regioselective separation was a competition between
the relative stabilities and solubilities of the complexes in the
water and water-DMSO solvents. The stabilities of the complexes in
water were assessed by the number of hydrogen bonding interactions
between the two γ-CDx units using molecular dynamics simulations.
To the best of our knowledge, this is the first reported example of
the isolation of the different regioisomers of fullerene derivatives
using host–guest complexes