New Molecular Devices: In Search of a Molecular Ratchet

• DOI: 10.1021/jo9723218
• Publication Date: 2002-07-26T05:24:06Z
• Authors: T. Ross Kelly; José Pérez Sestelo; Imanol Tellitu
• Keywords: Triptycene; Helicene; Molecular machine

The triptycene-substituted [3]- and [4]helicenes 1 2 were examined as possible molecular versions of mechanical ratchets, where the triptycene serves ratchet wheel helicenes pawl spring. syntheses 2b are described. 1H NMR was employed to examine rotation around triptycene/helicene single bond; at 20 °C is frozen for both 2b, but revealed a plane symmetry, indicating that cannot function unidirectional ratchet. In contrast, that, like ratchet, triptycyl[4]helicene lacks symmetry has barrier 24.5 kcal/mol, spin polarization transfer experiments indicated in nonetheless rotates equally directions. That outcome rationalized from standpoint thermodynamics.