Biomedical Engineering Reference
Fig. 7 Structural formula of the rotaxane 9 6+ ( top ) and schematic representation of its operation as
an autonomous “four-stroke” linear nanomotor powered by light ( bottom )
transfer process from A 1 − (still encircled by R) to the oxidized photoactive unit,
P + (process 5).
(c) Electronic reset : A back electron transfer process from the “free” A 1 − station to
P + (process 6) restores the electron acceptor power to the A 1 station.
(d) Nuclear reset : As a consequence of the electronic reset, back movement of the
ring by Brownian motion from A 2 to A 1 takes place (process 7).
The crucial point for such a mechanism is indeed the favorable competition
between ring displacement (process 4) and back electron transfer (process 5).
The rate constants of the relevant electron transfer processes were measured by