Half-rotation in a [2]catenane via interconvertible Pd(II) coordination modes

Area of Science:

• Supramolecular chemistry
• Coordination chemistry
• Organic synthesis

Background:

• [2]Catenanes are mechanically interlocked molecules with unique topological properties.
• Metal-templated synthesis and self-assembly are key strategies in supramolecular chemistry.
• Understanding metal-ligand interactions is crucial for designing complex molecular architectures.

Purpose of the Study:

• To investigate the coordination behavior of [2]catenanes with different palladium(II) salts.
• To elucidate how metal coordination influences the relative orientation of catenane components.
• To explore the structural consequences of metal binding in solution and solid states.

Main Methods:

• Synthesis of a specific [2]catenane precursor.
• Reaction of the [2]catenane with palladium(II) acetate (Pd(OAc)2) and palladium(II) chloride (PdCl2).
• Structural characterization using techniques such as NMR spectroscopy and X-ray crystallography.

Main Results:

• Pd(OAc)2 coordinates to both macrocyclic units of the [2]catenane, effectively locking them in a specific conformation.
• PdCl2 coordinates to only one of the macrocyclic units, leading to a significant change in the relative orientation of the components.
• This differential coordination results in a 'half-turn' in the [2]catenane structure, observed in both solution and solid-state.

Conclusions:

• The choice of palladium salt dictates the binding mode and structural outcome in [2]catenane-metal complexes.
• Metal coordination can be used as a tool to control the topology and conformation of mechanically interlocked molecules.
• This study provides insights into the precise control of supramolecular architectures through selective metal binding.