Page 99 - Science at the nanoscale

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June 12, 2009
4.4. From Molecules to Supramolecules
spontaneously through weak interactions.
Molecular self-
assembly has allowed the construction of very complex and chal-
lenging molecular architectures that would have been too tedious
to prepare in a stepwise sequential manner. Self-assembly phe-
nomena are not new and we can look to nature for inspiration.
The formation of micelles and monolayers of surfactant molecules
(Chapter 5) is an example of self-assembly. The self-assembly
technique is also utilized in the bottom-up fabrication of nano-
materials as will be discussed further in Chapter 7.
The preparation and assembly of many supramolecules have
been demonstrated in the literature. The French chemist Jean-
Marie Lehn is one of the pioneers in this field and was awarded
12
the Nobel Prize
in 1987 for his contribution to the synthesis of
cryptands and the field of supramolecular chemistry. The reader
is referred to the monograph written by Professor Lehn for more
13
In the fol-
details on the design principles of supramolecules.
lowing, we will discuss two examples of supramolecules that
have attracted much attention for their potential uses as molec-
ular machines (Fig. 4.28).
4.4.3
Molecular Machines
The
Figure 4.28(a) shows a rotaxane-based supramolecule.
molecule may be viewed as an interlocking architecture consisting
Figure 4.28. Schematic drawings of two supramolecules: (a) an assem- 89 ch04
bly of a rotaxane 14 and (b) an assembly of a catenane. 15
12
The prize was shared together with D. Cram and C. Pedersen for independent
work in the area.
13 J.-M. Lehn, Supramolecular Chemistry, Wiley-VCH (1995)
14 C. A. Stanier, M. J. O Connell, H. L. Anderson and W. Clegg, J. Chem. Soc. Chem.
Comm., 493 (2001).
15 M. Cesario, C. O. Dietrich-Buchecker, J. Guilhem, C. Pascard and J. P. Sauvage, J.
Chem. Soc. Chem. Comm. 244 (1985).