Qualitative Guest Sensing via Iron(II) Triazole Complexes

Area of Science:

• Coordination Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• The pyridazine-pyridine triazole ligand (L^pydzpy) was designed as a potentially ditopic chelator for metal ions.
• Investigating the coordination behavior of L^pydzpy with iron(II) is crucial for developing new functional materials.

Purpose of the Study:

• To synthesize and characterize novel mononuclear iron(II) complexes with the L^pydzpy ligand.
• To explore the spin crossover properties and guest sorption capabilities of these iron(II) complexes.

Main Methods:

• Synthesis of mononuclear iron(II) complexes: [Fe^II(L^pydzpy)₂(NCE)₂]·solvent (E = S, Se).
• Structural characterization using single-crystal X-ray diffraction (XRD).
• Evaluation of spin crossover activity via variable-temperature optical microscopy and magnetometry.
• Assessment of guest sorption using powder XRD and thermogravimetric analysis.

Main Results:

• Ten new mononuclear iron(II) complexes were synthesized, with L^pydzpy binding in a monotopic bidentate fashion.
• Seven of the complexes displayed spin crossover (SCO) activity.
• Desolvated polymorphs (1' and 2') showed reversible sorption of volatile guests like acetonitrile, tetrahydrofuran, and chloroform.

Conclusions:

• The L^pydzpy ligand forms stable mononuclear iron(II) complexes with tunable SCO properties.
• The desolvated complexes exhibit potential as porous materials for gas storage or separation.