Hysteretic spin crossover in isomeric iron(ii) complexes

Area of Science:

• Inorganic Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Spin crossover (SCO) is a phenomenon where certain transition metal complexes can switch between low-spin and high-spin states.
• Iron(II) complexes are widely studied for SCO due to their accessible spin states and potential applications.
• Pyrimidine-based ligands offer unique coordination environments that can influence SCO properties.

Purpose of the Study:

• To synthesize and characterize novel mononuclear iron(II) complexes featuring isomeric N,N,N-tridentate pyrimidine-based ligands.
• To investigate the spin crossover behavior of these newly synthesized complexes.
• To elucidate the mechanism underlying the spin switching, particularly the role of cooperativity and autocatalysis.

Main Methods:

• Synthesis of two mononuclear iron(II) complexes using isomeric N,N,N-tridentate pyrimidine-based ligands.
• Characterization of the complexes using standard spectroscopic and analytical techniques.
• Investigation of spin crossover properties through variable-temperature magnetic susceptibility measurements.
• Analysis of the switching mechanism, including cooperativity and autocatalysis.

Main Results:

• Successful synthesis of two distinct mononuclear iron(II) complexes with isomeric pyrimidine ligands.
• Both complexes demonstrated reproducible hysteretic spin crossover behavior.
• The transition from the low-spin to the high-spin state was observed to be cooperative.
• Evidence suggests that autocatalysis plays a crucial role in the cooperative spin switching.

Conclusions:

• The synthesized iron(II) complexes with isomeric pyrimidine ligands exhibit robust and hysteretic spin crossover.
• The observed spin switching is a cooperative process, facilitated by autocatalysis.
• These findings contribute to the understanding of SCO mechanisms and the design of new spin crossover materials.