Chemistry Reference
In-Depth Information
Roald Hoffmann has defined nanotechnology as the “The marriage of the syn-
thetic talent of Chemists with a 'device driven' ingenuity” [
41
]. Roald Hoffmann
reacted in this way when asked about the goal of nanotechnology: “I'm glad you guys
(that includes women, of course) found a new name for chemistry. Now you have the
incentive to learn what you didn't want to learn in college. Chemists have been
practicing nanotechnology, structure and reactivity and properties, for two centuries,
and for 50 years by design. What is exciting about modern nanotechnology is (a) the
marriage of chemical synthetic talent with a direction provided by “device-driven”
ingenuity coming from engineering, and (b) a certain kind of courage provided by
those incentives, to make arrays of atoms and molecules that ordinary, no, extraordi-
nary chemists just wouldn't have thought of trying. Now they're pushed to do so. And
of course they will. They can do anything. Nanotechnology is the way of ingeniously
controlling the building of small and large structures, with intricate properties; it is
the way of the future, a way of precise, controlled building, with, incidentally,
environmental benignness built in by design.” Indeed, the macroscopic concepts
of a device and a machine have been extended by chemists to the molecular level
[
39
,
40
,
42
-
54
]. A
molecular-level device
can be defined as an assembly of a discrete
number of molecular components (that is, a supramolecular structure) designed to
achieve a specific function. Each molecular component performs a single act, while
the entire supramolecular assembly performs a more complex function, which results
from the cooperation of the various components. A
molecular-level machine
is a
particular type of molecular-level device in which the component parts can display
changes in their relative positions as a result of some external stimulus. Like
macroscopic devices and machines, molecular-level devices and machines need
energy to operate and signals to communicate with the operator.
Interestingly, the bottom-up approach to the construction of molecular level
devices and machines was poetically anticipated by Primo Levi in his already-cited
book
The Monkey's Wrench
[
55
]:
It is reasonable to proceed a bit at a time, first attaching two pieces, then adding a third, and
so on.
If we had those
tweezers (and it's possible that, one day, we will), we would have managed to create some
lovely things that so far only the Almighty has made, for example, to assemble - perhaps
not a frog or a dragonfly - but at least a microbe or the spore of a mold.
Up until now, nobody has succeeded in constructing a chemical system as
complex as a microbe or the spore of a mold; in recent years, however, a number
of very simple molecular-level devices and machines have been built.
...
we don't have those tweezers we often dream of at night
...
7 Molecular Devices
7.1 Molecular Plug/Socket System
Supramolecular species, whose components are connected by means of non-covalent
forces, can be disassembled and re-assembled [
56
] by modulating the interactions
