Selective anion encapsulation in solid-state Ln(III)[15-metallacrown-5]3+ compartments through secondary sphere...

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Metallocavitands are macrocyclic compounds with potential applications in molecular recognition and separation.
• Anion selectivity in host-guest chemistry is crucial for various chemical processes.
• Lanthanide (Ln(III)) complexes offer unique electronic and magnetic properties.

Purpose of the Study:

• To investigate the role of proximal phenyl side chains in controlling anion selectivity of dimeric Ln(III) metallocavitands.
• To understand the mechanism by which secondary sphere interactions influence guest binding.
• To explore the potential of these metallocavitands for selective dicarboxylate binding.

Main Methods:

• Synthesis and characterization of dimeric Ln(III)[15-MC(Cu(II),α-aminoHA)-5](3+) metallocavitands with varying phenyl side chains.
• Anion binding studies using techniques like Isothermal Titration Calorimetry (ITC) and Nuclear Magnetic Resonance (NMR) spectroscopy.
• Computational modeling to elucidate interaction energies and binding pathways.

Main Results:

• The presence and orientation of phenyl side chains significantly impact the anion selectivity of the metallocavitands.
• Specific CH-O interactions were identified as key factors enabling the binding of saturated dicarboxylates.
• These secondary sphere interactions were found to overcome an intrinsic energy barrier for guest encapsulation within the hydrophobic compartments.

Conclusions:

• Secondary sphere interactions, particularly CH-O interactions mediated by phenyl side chains, are critical for tuning the anion selectivity of dimeric Ln(III) metallocavitands.
• The findings provide insights into the rational design of host molecules for selective anion recognition.
• This work contributes to the development of advanced materials for separation and sensing applications.