Chemistry Reference
In-Depth Information
Fig. 21 Redox controlled movements of the ring components in catenane 19H
2
6+
, composed of
three interlocked macrocycles. These motions are obtained upon reduction-oxidation of the
bipyridinium units of the cyclophane [
87
]
of the ring in the deprotonated catenane 18
4
þ
,itisnecessary
both
to reduce (switch
off) the bipyridinium units
and
protonate (switch on) the amine function. The
mechanical motion in such a catenane occurs according to an AND logic [
88
], a
function associated with two energy inputs of different nature.
Controlled rotation of the molecular rings has also been achieved in catenanes
composed of three interlocked macrocycles. For example, catenane 19H
2
6
þ
(Fig.
21
) is made up of two identical dioxybenzene-based macrocycles interlocked
with a cyclophane containing two bipyridinium and two ammonium units [
87
].
Because of the type of the macrocycles used, the stable conformation of 19 H
2
6
þ
is that in which the two rings surround the bipyridinium units. Upon addition of one
electron in each of the bipyridinium units, the two macrocycles move on the
ammonium stations, and move back to the original position when the bipyridinium
units are reoxidized.
It should be remarked that for the described catenanes, but also for most of the
catenane-based machines developed so far, the repeated switching between the two
translational states does not need to occur through a full rotation. In fact, because of
