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coefficients obtained from DOSY experiments of the catenane and
ligand
showed that the catenane is significantly larger
than its components. The signals from ligand and macrocycle
BPP34C10
L8
·2PF
6
displayed the same diffusion coefficients indicating that
the components diffuse as a whole. The location of the hydroquinol
units inside the cavity of the metallomacrocycle was also confirmed
by the cross-peaks between the aromatic protons of these units and
bipyridinium and the phenylene protons of the ligand observed
in a 2D rotating frame Overhauser effect spectroscopy (ROESY)
spectrum.
II
Scheme 11.4
Self-assembly
of
a
[3]catenane
based
on
trans
Pd
complexes.
The fact that, in acetonitrile, the dicationic ligand
L8
·2PF
and
6
the macrocycle
BPP34C10
are in a dissociated state [33] indicates
II
generates species with
enough π-electron deficient character in order to be inserted into
BPP34C10
that the coordination of
L8
·2PF
to Pd
6
.
11.5.4
Regioselective Catenation
Controlling noncovalent interactions such as hydrogen bonding,
π
stacking, hydrophobic forces, and coordinative bonds has
been the key to the success of synthetic strategies based on self-
assembly processes. Therefore, fine-tuning and full understanding
of how these subtle interactions govern these processes can be very
helpful in designing new supramolecular entities. As in the classical
covalent synthetic chemistry, regioselectivity must be understood
and controlled, as this type of control is intrinsically necessary over
self-assembly processes.
-
π
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