been prepared and investigated as light‐driven molecularbrakes that have different‐sized brake components (1 H<1 OM<1 NO<1 Pr<1 Bu). At room temperature (298 K), rotation of the pentiptycene rotor is fast (krot=108–109 s−1) with little interaction with the brake component in the trans form ((E)‐1 R), which corresponds to the brake‐off state. When the brake is turned on by photoisomerization to the cis