Experimental and theoretical studies on halide binding with a p-xylyl-based azamacrocycle

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Computational Chemistry

Background:

• Macrocyclic ligands are crucial in host-guest chemistry.
• Understanding halide binding is important for chemical sensing and separation.
• Developing selective anion receptors remains a challenge.

Purpose of the Study:

• To synthesize a p-xylyl-based macrocycle (L).
• To investigate the binding properties of L with various halide anions.
• To elucidate the binding mode and strength using experimental and computational methods.

Main Methods:

• Synthesis of a p-xylyl-based macrocycle.
• (1)H NMR titrations to determine binding constants.
• Single crystal X-ray diffraction to analyze complex structures.
• Density Functional Theory (DFT) calculations for binding energies.

Main Results:

• The ligand L preferentially binds halides in a 1:2 stoichiometry.
• Binding affinity follows the order: fluoride > chloride > bromide > iodide.
• X-ray diffraction confirmed 1:2 complexes with chloride, bromide, and iodide.
• DFT calculations support the experimental binding trend and favor 1:2 binding.

Conclusions:

• The synthesized macrocycle exhibits selective halide binding.
• Binding strength is influenced by halide basicity and size.
• The 1:2 binding mode is energetically favored, demonstrating potential for anion recognition.