Pumping a Ring-Sliding Molecular Motion by a Light-Powered Molecular Motor

Designing artificial
molecular machines to execute complex mechanical
tasks, like coupling rotation and translation to accomplish transmission
of motion, continues to provide important challenges. Herein, we demonstrated
a novel molecular machine comprising a second-generation light-driven
molecular motor and a bistable [1]­rotaxane unit. The molecular motor
can rotate successfully even in an interlocked [1]­rotaxane system
through a photoinduced cis-to-trans isomerization and a thermal helix inversion, resulting in concomitant
transitional motion of the [1]­rotaxane. The transmission process was
elucidated via 1H NMR, 1H–1H COSY, HMQC, HMBC, and 2D ROESY NMR spectroscopies, UV–visible
absorption spectrum, and density functional theory calculations. This
is the first demonstration of a molecular motor to rotate against
the appreciably noncovalent interactions between dibenzo-24-crown-8 and N-methyltriazolium moieties
comprising the rotaxane unit, showing operational capabilities of
molecular motors to perform more complex tasks.