An ultrafast surface-bound photo-active molecular motor.

We report the synthesis and surface attachment of an ultrafast light-driven rotary molecular motor. Transient absorption spectroscopy revealed that the half-life of the rate determining thermal step of the rotary cycle in solution is 38 ± 1 ns, the shortest yet observed, making this the fastest molecular motor reported. Incorporation of acetylene legs into the structure allowed the motors to be grafted to azide-modified quartz and silicon substrates using the "click" 1,3-dipolar cycloaddition reaction.

Ultrafast light-driven nanomotors based on an acridane stator.

A series of molecular motors featuring a symmetrical acridane stator is reported. Photochemical and thermal isomerization experiments confirm that this stator, in combination with a thiopyran rotor, results in molecular rotary motion in which the rate-determining thermal helix inversion proceeds effectively only at temperatures above 373 K. The introduction of a cyclopentanylidene rotor unit results in a decrease in steric hindrance with respect to the stator, and as a consequence, a 10(12)-fold increase in the rate of thermal helix inversion is observed. Nanosecond transient absorption spectroscopy allows for the thermal processes to be followed accurately at ambient temperature. The rotary motor is shown to be able to operate at 0.5 MHz rotational frequencies under optimal conditions.