Superchiral Pd3 L6 Coordination Complex and Its Reversible Structural Conversion into Pd3 L3 Cl6 Metallocycles

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Chiral Ligand Design

Background:

• Chiral ligands derived from natural products offer unique structural motifs.
• Bile acids provide a readily available source of chirality for complex synthesis.

Purpose of the Study:

• To synthesize and characterize novel superchiral coordination complexes using a chiral bispyridyl ligand derived from ursodeoxycholic acid.
• To investigate the structural transformations and stability of these palladium-based supramolecular assemblies.

Main Methods:

• Square-planar coordination of tetravalent palladium(II) with the chiral ligand.
• Characterization using NMR spectroscopy (1H DOSY), mass spectrometry, circular dichroism, and ion-mobility mass spectrometry.
• Structural analysis through molecular modeling.

Main Results:

• Formation of a cationic single enantiomer superchiral complex (1 Pd3 L6) with a flower-like structure and 60 chiral centers.
• Reversible transformation of complex 1 into an enantiomerically pure cyclic trimer (2 Pd3 L3 Cl6) with 30 chiral centers upon chloride addition.
• Direct synthesis of constitutional isomers of trimers and dimers by coordinating the ligand to different palladium(II) geometries.

Conclusions:

• The study demonstrates the successful synthesis of complex, stable, and water-resistant chiral supramolecular assemblies.
• The ligand's versatility allows for the creation of diverse structures with tunable chirality.
• These findings open avenues for the development of new chiral materials and catalysts.