General strategy for boosting the performance of speed-tunable rotary molecular motors with visible light

Light-driven molecular rotary motors perform chirality-controlled unidirectional rotations fueled by light and heat. This unique function renders them appealing for the construction of dynamic molecular systems, actuating materials, and molecular machines. Achieving a combination of high photoefficiency, visible-light responsiveness, synthetic accessibility, and easy tuning of dynamic properties within a single scaffold is critical for these applications but remains a longstanding challenge. Herein, a series of highly photoefficient visible-light–responsive molecular motors (MMs), featuring various rotary speeds, was obtained by a convenient one-step formylation of their parent motors. This strategy greatly improves all aspects of the performance of MMs—red-shifted wavelengths of excitation, high photoisomerization quantum yields, and high photostationary state distributions of isomers—beyond the state-of-the-art light-responsive MM systems. The development of this late-stage functionalization strategy of MMs opens avenues for the construction of high-performance molecular machines and devices for applications in materials science and biological systems, representing a major advance in the synthetic toolbox of molecular machines.