Engineering Highly Photoefficient and Function-Tunable Molecular Rotary Motors toward Sunlight Responsiveness.

The construction of light-driven molecular rotary motors capable of unidirectional rotation holds great promise for the construction of smart, adaptive systems and dynamic materials. Designing molecular structures that combine high photoefficiency, tunable functionality, and robust structural integrity is critical for advancing these applications. Herein, we present a molecular engineering strategy to access a family of highly photoefficient first-generation molecular motors (MMs) bearing diverse functional groups through late-stage modification of a typical motor scaffold. This systematic investigation demonstrates that the photoefficiency, functional properties, and rotary speed of molecular motors can be precisely tuned through relatively simple structural modifications and identifies para-formylation as a key design principle for markedly enhancing the photoefficiency of future motor scaffolds. The photoefficient MMs exhibit exceptional responsiveness to sunlight both in solution and within a polystyrene polymer matrix, opening unique opportunities for the construction of high-performance MMs with tailored functionalities for materials science and dynamic molecular systems. This work expands the synthetic toolbox of molecular machines and inspires future molecular design strategies.