Molecular Spur Gears Comprising Triptycene Rotators and Bibenzimidazole-Based Stators

Dynamic gearing of molecular spur gears, the most common
type of
mechanical gear, is elucidated. Molecular design and conformational
analysis show that derivatives of 4,4-bis­(triptycen-9-ylethynyl)­bibenzimidazole
represent suitable constructs to investigate gearing behavior of collateral
triptycene (Tp) groups. To test this design, DFT calculations (B97-D/Def2-TZVP)
were employed and the results suggest that these molecules undergo
geared rotation preferentially to gear slippage. Synthesis of derivatives
was carried out, providing a series of molecular spur gears, including
the first desymmetrized spur gear molecules, which were subsequently
subjected to stereochemical analysis.