Protonation-Gated Orthogonal Control of Highly Efficient Molecular Motors With Broad Visible-Light Responsiveness

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Photochemistry

Background:

• Molecular motors are crucial for biomedical applications but achieving red-shifted absorption is challenging.
• Conventional methods to extend excitation wavelengths often reduce photochemical efficiency and motor function.

Purpose of the Study:

• To develop a novel protonation-gated strategy for molecular motors.
• To enable state-dependent motor operation across a broad visible-light window without compromising efficiency.

Main Methods:

• Synthesized coumarin-derived overcrowded alkenes with benzazole substituents.
• Utilized photophysical studies and Density Functional Theory (DFT) calculations.
• Investigated the effect of protonation on motor conformation and electronic properties.

Main Results:

• Protonation induced conformational inversion and intramolecular hydrogen bonding, leading to molecular planarization.
• Achieved efficient photoisomerization under blue-green light (450-500 nm) and visible light (530-600 nm).
• Maintained quantitative photoconversion and motor function across the tested wavelengths.

Conclusions:

• Reversible protonation is a powerful strategy to expand visible-light responsiveness of molecular motors.
• This method allows tuning motor operation without permanent structural changes.
• The developed motors show potential for multimodal responsive bioimaging and advanced optical devices.