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All-Photochemical Rotation of Molecular Motors with a Phosphorus Stereoelement

2020; American Chemical Society; Volume: 142; Issue: 39 Linguagem: Inglês

10.1021/jacs.0c08249

1943-2984

Gregory B. Boursalian, Eise Nijboer, Ruth Dorel, Lukas Pfeifer, Omer Markovitch, Alex Blokhuis, Ben L. Feringa,

Porphyrin and Phthalocyanine Chemistry

Unidirectional molecular rotation based on alternating photochemical and thermal isomerizations of overcrowded alkenes is well established, but rotary cycles based purely on photochemical isomerizations are rare. Herein we report three new second-generation molecular motors featuring a phosphorus center in the lower half, which engenders a unique element of axial chirality. These motors exhibit unusual behavior, in that all four diastereomeric states can interconvert solely photochemically. Kinetic analysis and modeling reveal that the behavior of the new motors is consistent with all-photochemical unidirectional rotation. Furthermore, X-ray crystal structures of all four diastereomeric states of two of these new motors were obtained, which constitute the first achievements of crystallographic characterization of the full 360° rotational cycle of overcrowded-alkene-based molecular motors. Finally, the axial phosphorus stereoelement in the phosphine motor can be thermally inverted, and this epimerization enables a "shortcut" of the traditional rotational cycle of these compounds.