XAFS studies and computational simulation of calixcrowns-caesium complexes in solution

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Analytical Chemistry

Background:

• Calixarene crown-6 compounds are crucial in host-guest chemistry, particularly for ion complexation.
• Understanding the local structure and interactions of caesium ions with these hosts is vital for applications in separation and sensing.

Purpose of the Study:

• To investigate the local structure and coordination environment of caesium ions complexed with BPC6, BOC6, and BisC6 ligands.
• To evaluate the influence of different solvents (NPME and OA) on caesium ion interactions.
• To compare experimental X-ray absorption spectroscopy data with theoretical density functional theory calculations.

Main Methods:

• Caesium L(3)-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy.
• Density functional theory (DFT) calculations using a triple-zeta basis set with polarization functions.

Main Results:

• XANES data indicated enhanced molecular symmetry upon caesium ion embedding within the ligands.
• EXAFS analysis revealed specific coordination numbers (N ≈ 7) and average distances (R ≈ 3.2-3.3 Å) between caesium and oxygen atoms.
• DFT simulations supported the experimental findings, providing theoretical distances for caesium-oxygen coordination.

Conclusions:

• Caesium ion complexation with BPC6, BOC6, and BisC6 ligands leads to a well-defined local structure with enhanced symmetry.
• The coordination environment is consistent across different calixarene crown-6 derivatives and solvents, with minor variations in distances.
• X-ray absorption spectroscopy and DFT calculations provide complementary insights into the supramolecular interactions of caesium ions.