Dicyanometalates as Building Blocks for Multinuclear Iron(II) Spin-Crossover Complexes

Area of Science:

• Coordination Chemistry
• Materials Science
• Magnetochemistry

Background:

• Spin-crossover (SCO) complexes are of interest for molecular switches and memory devices.
• Designing heterometallic complexes with tunable SCO properties is a key challenge.
• Dicyanometalates offer versatile bridging capabilities in coordination chemistry.

Purpose of the Study:

• To synthesize novel heterometallic hexanuclear iron(II) complexes.
• To investigate the spin-crossover behavior of these new complexes.
• To explore the role of dicyanometalate linkers in SCO properties.

Main Methods:

• Synthesis of heterometallic complexes using tris(2-pyridylmethyl)amine (tpma) and S,S'-bis(2-pyridylmethyl)-1,2-thioethane (bpte) ligands.
• Utilizing [Ag(CN)2]- and [Au(CN)2]- as N-coordinating ditopic linkers.
• Characterization through X-ray crystallography and variable-temperature magnetic susceptibility measurements.

Main Results:

• Formation of heterometallic hexanuclear complexes {[Fe(tpma)]4(μ-CN)2[μ-Ag(CN)2]2}(ClO4)4·3H2O (1) and {[Fe(tpma)]2[μ-Au2(CN)4]2} (2).
• Synthesis of an analogous complex {[Fe(bpte)]2[μ-Au2(CN)4]2} (3) using a mixed-donor ligand.
• Complexes 1-3 exhibit onset of spin-crossover (SCO) behavior above 350 K.
• Complex 2 shows gradual spin-state conversion above 400 K.

Conclusions:

• Novel heterometallic iron(II) complexes with dicyanometalate linkers were successfully synthesized.
• These complexes demonstrate spin-crossover behavior, indicating potential for molecular device applications.
• The choice of metal (Ag vs. Au) and capping ligand influences complex formation and stability.