Molecular Rotor Functionalized with a Photoresponsive Brake

A molecular motor that has been previously shown to rotate when fueled by electrons through a scanning tunneling microscope tip functionalized with terarylene photochrome fragment on its rotating subunit. Photoisomerization performed under UV irradiation. Variable-temperature 1H NMR and UV–vis studies demonstrate the rotational motion braking action after photoisomerization. The can be reversed thermal heating. Once rigid planar closed form is obtained, rotation effectively slowed at lower temperature, making this new rotor potential an independent response light.