Chemistry Reference
In-Depth Information
Fig. 29 Solid-state structure
of the doubly interlocked [2]
catenane (Solomon Knot) that
emerges unexpectedly from a
DCL containing DAB, DFP,
and a 1:1 mixture of Zn
2+
and
Cu
2+
templates [
217
]
iodide-catalyzed self-assembly of donor-acceptor [2]catenanes (Fig.
27d
) was applied
to a polymerizable “blue box”monomer in 84%yield.When dimerized, the catenation
proceeded in an unsurprising 49% yield. However, when the catenation was
performed on the polymerized species, the reaction unexpectedly went to
99%
completion (Fig.
30
). This result [
207
] was subsequently rationalized by postulating
a cooperative, synergistic templating effect by nearby cyclophanes on the backbone of
the polymer that would not be present in the monomeric and dimeric compounds.
Though there are plenty of gray areas on the subject of complexity and emer-
gence, spectacular examples in the field of MIMs are still rare, but the chemistry of
complexity is sure to become a growing, exciting, and pleasing new direction that
chemists will inevitably take.
>
Structure
Catenation Yield
R =
O
O
O
R
84%
O
O
R
+
N
+
N
N
N
N
N
49%
N
N
R
+
+
N
O
N
Br
O
EtO
O
n
>99%
O
O
O
O
O
O
O
N
O
R
N
O
N
Fig. 30 Polymeric “blue box” cyclophane displays the emergent property of quantitative thermo-
dynamic catenation by iodide-catalyzed self-assembly with an appropriate crown ether
macrocycle. The analogous monomeric and dimeric species do not react quantitatively [
207
]
4.5 Beautiful Mechanically Interlocked Molecular Machines
and Switches
We live in an era that beautifies machines, from automobiles to computers. Argu-
ably the most compelling aspect of MIMs - at least those templated by noncovalent
bonding interactions - is their susceptibility to controlled mechanical motion of
