Halide-triggered assembly and selective bisulfate recognition in a quadruply interlocked coordination cage

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry

Background:

• Interlocked coordination cages are versatile multi-cavity architectures.
• Controlling guest partitioning within these cages is crucial but challenging.

Purpose of the Study:

• To design and synthesize a novel coordination cage with tunable cavity partitioning.
• To investigate the templating effect of anions on cage interpenetration and guest binding.

Main Methods:

• Assembly of a [Pd2L4](BF4)4 cage using a bis-monodentate ligand.
• Characterization using Nuclear Magnetic Resonance (NMR), Electrospray Ionization Mass Spectrometry (ESI-MS), and X-ray crystallography.
• Thermodynamic stability and binding affinity studies in acetonitrile (MeCN).

Main Results:

• Halides (Cl-, Br-) templated the interpenetration of the cage into a [X@Pd4L8]7+ dimer.
• The halide anion was selectively encapsulated in the central pocket of the interlocked dimer.
• The interlocked host exhibited exceptionally high binding affinity (up to 10^6 M^-1) for bisulfate anions in its outer pockets, outcompeting similar tetrahedral anions.

Conclusions:

• The study demonstrates a successful strategy for controlling cage interpenetration and anion partitioning through ligand design and templating.
• The developed interlocked cage shows potential for highly selective anion recognition, particularly for bisulfate.
• This work contributes to the advancement of adaptive sensing and host-guest chemistry.