Spin-crossover iron(ii) long-chain complex with slow spin equilibrium at low temperatures

Area of Science:

• Inorganic Chemistry
• Materials Science
• Physical Chemistry

Background:

• Spin crossover (SCO) is a phenomenon where transition metal complexes can switch between low-spin and high-spin states.
• Controlling SCO behavior is crucial for developing molecular switches and sensors.
• Slow spin dynamics can limit the practical applications of SCO materials.

Purpose of the Study:

• To synthesize a mononuclear iron(II) complex with long alkyl chains.
• To investigate the spin crossover properties of the synthesized complex.
• To explore methods for improving SCO completeness by addressing slow spin equilibrium.

Main Methods:

• Synthesis of a mononuclear iron(II) complex, [Fe(H2Bpz2)2(C9bpy)] (1).
• Single-crystal X-ray crystallography to determine the structural characteristics.
• Magnetic measurements to probe the spin crossover behavior.
• Variable temperature magnetic susceptibility studies.
• Investigating the effect of scan rate, annealing, light irradiation, and pressure on SCO.

Main Results:

• The complex [Fe(H2Bpz2)2(C9bpy)] (1) was successfully synthesized.
• X-ray crystallography showed co-crystallization of Δ- and Λ-enantiomers.
• The complex exhibited incomplete one-step spin crossover due to slow spin equilibrium.
• SCO completeness and transition temperature were found to be dependent on measurement velocity.
• Multivariable approaches were effective in enhancing SCO completeness.

Conclusions:

• The synthesized iron complex displays complex spin crossover behavior influenced by slow spin dynamics.
• Understanding and manipulating slow spin equilibrium is key to achieving complete SCO transitions.
• The explored methods offer potential strategies for optimizing SCO materials for device applications.