English

• Light-driven artificial molecular machines [1,2] are a class of functional small molecules powered by photochemical reactions, broadly divided into molecular motors and molecular photoswitches. Molecular motors [3,4], owing to their intrinsic point chirality and dynamic axial chirality, undergo unidirectional rotation about a carbon–carbon double bond when irradiated with light. In nature, biological molecular motors and pumps are ubiquitous: driving vision, intracellular transport, energy conversion, signal transduction, muscle contraction, and locomotion. Chemists have drawn inspiration from these systems to synthesize nanoscale artificial machines such as rotary motors and molecular pumps, which promise transformative applications in intelligent materials. However, artificial molecular motors and photoswitches still face critical bottlenecks: low photoisomerization quantum yields, excitation wavelengths confined to the ultraviolet region, and poor photostationary-state distributions, all of which hinder their efficiency, stability, and biocompatibility.

  Inspired by natural retinal-based systems, the Ben Feringa group pioneered a late-stage Rieche formylation strategy for first-generation overcrowded alkene motors, achieving transformative performance enhancements [5]. The introduced aldehyde substituent induced a bathochromic shift in absorption maxima, circumventing phototoxic UV irradiation, while attaining photoisomerization QYs (~100%) rivalling natural rhodopsin. Critically, this modification enabled full four-state directional interconversion under precise photothermal control (100% isomer yield). ortho-Hydroxy groups served dual roles as directing moieties and co-crystallization handles, facilitating scalable enantiopure motor resolution without chromatographic methods and advancing chiral dynamic system design.

  Expanding this approach to second-generation motors [6], the team implemented a single-step aldehyde functionalization to achieve (Fig. 1): (i) Absorption maxima redshifted to 415 nm, enabling efficient visible-light activation (405–420 nm); (ii) photoisomerization QYs of 26%–28%; (iii) PSS conversions exceeding conventional systems; and (iv) the first demonstration of bidirectional visible-light switching in overcrowded alkenes. Thermal relaxation half-lives were modulated across nanosecond-to-hour timescales, with motors exhibiting unprecedented fatigue resistance. This universal formylation strategy concurrently addresses spectral range limitations, energy-conversion efficiency, and dynamic tunability, surpassing π-extension, push-pull, and metal-coordination approaches, to establish a scalable paradigm for high-performance molecular machinery.

  Figure 1

  

  Figure 1.  Visible light–driven unidirectional molecular rotary motors and schematic representation of current strategy. Reproduced with permission [6]. Licensed under CC BY-NC 4.0.

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  This simple, late-stage aldehyde modification strategy solves the longstanding challenge of creating visible-light-responsive molecular motors with high photoefficiency, robust photostationary conversion, and easily tunable kinetics, all in broadly applicable scaffolds. This strategy is general and can also be extended to the construction of visible-light-driven photoswitches. By unifying redshifted activation, record quantum yields, complete isomer control, and programmable rotary speeds, from ultrafast to ultralow, this work delivers the first truly universal platform for next-generation artificial molecular machinery. Looking forward, integrating these formylated motors into supramolecular assemblies and responsive materials will enable programmable, light-driven actuation at the macroscale. Detailed mechanistic studies of their excited-state landscapes will further refine design rules for future molecular devices.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Youxin Fu: Writing – original draft, Conceptualization. Junji Zhang: Writing – review & editing, Supervision, Conceptualization.

  
  
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  Figure 1  Visible light–driven unidirectional molecular rotary motors and schematic representation of current strategy. Reproduced with permission [6]. Licensed under CC BY-NC 4.0.

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