Active and Unidirectional Acceleration of Biaryl Rotation by a Molecular Motor

Abstract

Light‐driven molecular motors possess immense potential as central driving units for future nanotechnology. Integration into larger molecular setups and transduction of their mechanical motions represents the current frontier of research. Herein we report on an integrated molecular machine setup allowing the transmission of potential energy from a motor unit onto a remote receiving entity. The setup consists of a motor unit connected covalently to a distant and sterically encumbered biaryl receiver. By action of the motor unit, single‐bond rotation of the receiver is strongly accelerated and forced to proceed unidirectionally. The transmitted potential energy is directly measured as the extent to which energy degeneration is lifted in the thermal atropisomerization of this biaryl. Energy degeneracy is reduced by more than 1.5 kcal mol−1, and rate accelerations of several orders of magnitude in terms of the rate constants are achieved.

Quantitative In‐Situ NMR Illumination for Excitation and Kinetic Analysis of Molecular Motor Intermediates

“…In multi‐step processes like the rotation cycle in HTI motors [20–22,26–29] (Figure 1) the analysis can be hampered if some intermediate isomers are photo‐populated with limited efficiency. In such cases the subsequent thermal depopulation of the primary photoproducts proceeds rather fast due to a low energy barrier for thermal helix inversion in these motors, which decreases the population of observable primary intermediates.…”

Sulfone “Geländer” Helices: Revealing Unexpected Parameters Controlling the Enantiomerization Process

“…Our investigation clearly shows that even a subtle change in bonding, such as the one that interconverts the constitutional isomers 1 and 2 , may have a decisive impact on the synergies of individual units that control the overall kinetic behavior of the extended system, as we observe for the helix inversion in 1 and 2 with only two coupled macrocycles. These findings can prove useful in designing configurationally persistent Geländer helices or complex molecular systems such as molecular motors, in which individual subunits are either weakly or strongly geared. − …”