A C2-symmetric, basic Fe(III) carboxylate complex derived from a novel triptycene-based chelating carboxylate ligand

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Triptycene-based ligands offer unique structural and steric properties for coordination chemistry.
• Bis(benzoxazole) diacids are versatile building blocks for metal-organic frameworks and complexes.
• Sterically encumbering groups can influence the self-assembly and properties of metal complexes.

Purpose of the Study:

• To synthesize a novel triptycene-based bis(benzoxazole) diacid ligand, H(2)L2(Ph4).
• To investigate the coordination behavior of H(2)L2(Ph4) with iron(III) ions.
• To characterize the resulting trinuclear iron(III) complex and its structural features.

Main Methods:

• Synthesis of the H(2)L2(Ph4) ligand.
• Complexation reaction of H(2)L2(Ph4) with Fe(OTf)(3).
• Single-crystal X-ray diffraction for structural determination of the iron complex.

Main Results:

• Successful synthesis of the H(2)L2(Ph4) ligand bearing sterically encumbering groups.
• Formation of a C(2)-symmetric trinuclear iron(III) complex, [NaFe(3)(L2(Ph4))(2)(μ(3)-O)(μ-O(2)CCPh(3))(2)(H(2)O)(3)](OTf)(2).
• The complex exhibits a 'basic iron acetate' core with heteroleptic carboxylate bridging, including the triptycene-based ligand.

Conclusions:

• The triptycene-based bis(benzoxazole) diacid ligand effectively coordinates to form a trinuclear iron(III) complex.
• The ligand's structure is largely retained upon complex formation, indicating its stability.
• The study demonstrates the utility of sterically demanding ligands in constructing complex metal architectures.