Chemistry Reference
In-Depth Information
spectroscopy [
92
]. This system is more complex than that described in Fig.
22
because it contains two independently addressable blocking groups. Hence, unidirec-
tional rotation is achieved with three pairs of different stimuli (one for driving the
co-conformational rearrangement, and two for the ratcheting of the energy barriers).
The time scales and number of reactions involved for unidirectional ring rotation in
catenane 20 and in other similar catenanes [
93
] make their operation as rotary motors
somewhat unpractical. Nevertheless, analysis of the thermodynamic and kinetic
aspects of the operation mechanisms provides a fundamental insight on how energy
inputs can be used to harness thermal fluctuations and drive unidirectional motion.
9 Conclusions
Chemistry is inside and around us: all the processes that sustain life are based on
chemical reactions, and most things we use in everyday life are natural (e.g., water,
wheat, oil, wood) or artificial (plastics, glass, medicines, pesticides) molecules. For
these reasons Chemistry is a central science. Its importance and extension can be
better perceived by a comparison with language. Molecules, the words of matter,
are the smallest entities that have distinct shapes, sizes and properties. Like words,
molecules contain specific pieces of information that are revealed when they
interact with one another.
Much more complex functions can be achieved by assembling molecules into
supramolecular systems. Upon excitation with chemical species, electrons, and
photons, suitably designed supramolecular systems can indeed perform a variety
of useful functions related to energy- and electron-transfer processes and to
mechanical movements.
Besides being important and useful, Chemistry has also a beautiful side that has
inspired writers, poets, and sculptors. Chemistry is a wonderful book that continues
to expand every day: new ideas and new concepts are developed, previously
unknown natural molecules are discovered, novel artificial molecules are
synthesized, more complex supramolecular species are assembled, and more and
more interesting molecular devices and machines are created.
Acknowledgments Authors acknowledge Alberto Credi for fruitful discussion and artistic
suggestions. Support by Alma Mater Studiorum
Universit
`
di Bologna, Ministero
dell'Universit
`
e della Ricerca (PRIN 2008HZJW2L), and Fondazione CARISBO is gratefully
acknowledged.
References
1. Greenberg A (2003) The art of chemistry - Myths, medicine, and materials. Wiley, Hoboken
2. Smith MF (2001) Lucretius: on the nature of things. Hackett, Indianapolis/Cambridge
3. The literary works of Leonardo da Vinci
,
compiled and edited from the original manuscripts by
Richter J-P, commentary by Pedretti C (1977) Phaidon, Oxford, p 102
