Spin Crossover in a Hexaamineiron(II) Complex: Experimental Confirmation of a Computational Prediction

Area of Science:

• Coordination Chemistry
• Materials Science
• Computational Chemistry

Background:

• Spin crossover complexes are crucial for molecular switches and sensors.
• Artificial evolution design methods can predict functional transition-metal complexes.
• Understanding spin transitions is key to developing novel electronic materials.

Purpose of the Study:

• To experimentally validate the spin crossover behavior of [Fe(tame)2]Cl2·MeOH.
• To investigate the electronic and structural changes associated with the spin transition.
• To provide insights into the design principles of spin crossover materials predicted by in silico methods.

Main Methods:

• Single crystal structural analysis at variable temperatures.
• Variable-temperature optical spectroscopy.
• Quantum chemical calculations and thermodynamic analysis (Ising-like mean field model).

Main Results:

• A smooth spin crossover was observed in [Fe(tame)2]Cl2·MeOH between high-spin and low-spin states without symmetry change.
• The crossover occurred at T1/2 = 140 K, confirmed by spectroscopy.
• Experimental results validated the in silico predicted spin activity of the complex.

Conclusions:

• The study provides the first experimental validation of a functional spin crossover complex designed via in silico methods.
• Structural and electronic analyses offer insights into spin-passive components influencing the crossover.
• Thermodynamic analysis yielded estimates for enthalpy, entropy, and cooperativity of the spin transition.