Light-Driven Ratchet Mechanism Accelerates Regioselective Metal-Cation Exchange in a Heterobimetallic Helicate

Area of Science:

• Supramolecular Chemistry
• Molecular Machines
• Coordination Chemistry

Background:

• Molecular machines require non-equilibrium processes to perform work.
• Developing non-equilibrium processes like molecular ratchets is an emerging field.

Purpose of the Study:

• To design and synthesize a novel diazocine-containing ligand for creating self-sorted dinuclear helicates.
• To investigate the photoisomerization mechanism of these helicates and their ability to operate via a molecular ratchet.
• To demonstrate the potential for controlled metal-cation exchange and adaptive supramolecular structures.

Main Methods:

• Synthesis of a diazocine-containing ligand (L) with distinct chelating sites.
• Formation of dinuclear homo- and heterobimetallic helicates through self-sorting.
• Photoisomerization studies under continuous white-light irradiation.
• Analysis of metal-cation exchange kinetics.

Main Results:

• Successfully formed precisely controlled dinuclear helicates ([FeII2L](OTf)4, [CoII2L](OTf)4, [ZnII2L](OTf)4, [ZnIIFeIIL](OTf)4, [ZnII CoIIL](OTf)4).
• Demonstrated photoisomerization via a molecular ratchet mechanism, leading to metastable diastereomers and deviation from thermodynamic equilibrium.
• Showcased selective enrichment of an out-of-equilibrium pseudo-mesocate structure.
• Observed accelerated metal-cation exchange in the [ZnII2L](OTf)4 helicate, driven by the ratchet mechanism.

Conclusions:

• The developed ligand enables the construction of helicates with controlled metal distribution.
• The molecular ratchet mechanism allows for autonomous operation away from thermodynamic equilibrium.
• This system functions as a molecular
• claw machine
• selectively capturing specific metal ions under external stimuli.
• Provides a foundation for adaptive and reconfigurable supramolecular architectures utilizing non-equilibrium phenomena.