Electrochemically and Photochemically Driven Ring Motions in a Disymmetrical Copper [2]-Catenate

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• The three-dimensional template effect of copper(I) has been instrumental in synthesizing complex interlocking ring systems.
• Designing molecules with distinct, interlocked components is a key challenge in supramolecular chemistry.
• Controlling molecular motion and shape through external stimuli is crucial for developing advanced molecular machines.

Purpose of the Study:

• To synthesize a new disymmetrical [2]-catenate incorporating 2,9-diphenyl-1,10-phenanthroline (dpp) and 2,2',6',2''-terpyridine (terpy) units.
• To investigate the dual coordination modes of the catenate with copper(I) and copper(II) ions.
• To explore the triggered molecular motion and shape changes between different coordination states.

Main Methods:

• Synthesis of the disymmetrical [2]-catenate using the copper(I) template effect.
• Complexation with copper(I) and copper(II) ions to form distinct coordination complexes.
• Electrochemical studies and UV-vis spectroscopy to analyze redox behavior and molecular motion.
• Investigation of counterion effects on the rate of molecular rearrangement.

Main Results:

• A novel disymmetrical [2]-catenate consisting of two different interlocking rings was successfully synthesized.
• Two distinct coordination modes were observed: copper(I) coordinating to dpp units, leaving terpy free, and copper(II) coordinating to terpy, with dpp at the periphery.
• Molecular motion between four- and five-coordinate states was triggered by changing the copper oxidation state, leading to different molecular shapes and properties.
• The rate of ring motion could be controlled, with slow rearrangement observed under certain conditions and rapid rearrangement induced by coordinating counterions like chloride.

Conclusions:

• The synthesized disymmetrical [2]-catenate functions as a molecular machine with switchable properties based on copper's oxidation state.
• The study demonstrates precise control over molecular motion and shape transformation in a complex supramolecular system.
• This work opens avenues for designing responsive materials and advanced molecular devices.