Programming Palladium Cage Geometry through Ligand Redox Modulation

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Redox-active ligands offer tunable properties in coordination chemistry.
• Metal-organic cages (MOCs) are versatile supramolecular structures with diverse applications.
• Controlling MOC assembly and properties through external stimuli is a key challenge.

Purpose of the Study:

• To design and synthesize redox-switchable coordination cages.
• To investigate how ligand oxidation state influences self-assembly and cage properties.
• To demonstrate reversible control over MOC nuclearity and composition.

Main Methods:

• Synthesis of an exTTF-based ditopic ligand (L).
• Self-assembly of palladium(II) complexes with L to form M2L4 cages.
• Oxidation of the ligand to L(ox) and subsequent self-assembly into M2L(ox)2 and M2L(ox)L'2 structures.
• Structural characterization using single-crystal X-ray diffraction.
• Demonstration of reversible redox-induced transformations.

Main Results:

• Formation of a M2L4 cage with selective binding for dinitrile alkanes.
• Oxidation of L to L(ox) redirected self-assembly to a M2L(ox)2 structure.
• Assembly of a heteroleptic M2L(ox)L'2 structure, which dimerized into an unprecedented M4L4L'4 architecture.
• Structural authentication of key intermediates and products.
• Reversible reduction of M2L(ox)L'2 back to the M2L4 cage.

Conclusions:

• Ligand redox state is a powerful tool for controlling metal-organic assembly.
• Reversible changes in oxidation state allow for dynamic modulation of MOC nuclearity and composition.
• This work provides a framework for designing responsive and switchable coordination cages.