Investigation of the two-step spin crossover complex Fe[5-NO2-sal-(1,4,7,10)] using density functional theory

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Understanding the electronic and structural properties of metal complexes is crucial for developing new materials.
• Iron(II) complexes exhibit diverse spin states influencing their physical properties.
• Conformational isomerism in metal complexes can significantly impact their behavior.

Purpose of the Study:

• To investigate the conformational isomerism of an iron(II) complex using quantum chemical calculations.
• To determine the electronic polarizability of the complex in different spin states and conformers.
• To correlate calculated electronic properties with experimental dielectric constant measurements.

Main Methods:

• Density Functional Theory (DFT) was employed for quantum chemical calculations.
• Geometry optimizations were performed starting from X-ray crystallographic structures.
• Multiple DFT functionals (B3LYP, B3LYP*, BP86, HCTH407) were utilized for method validation.

Main Results:

• Calculations confirmed the conformational isomerism of the Fe[5-NO2-sal-(1,4,7,10)] complex in both singlet (1A1g) and quintet (5T2g) spin states.
• DFT methods accurately reproduced the structural differences between conformers compared to experimental data.
• Electronic polarizability was found to be higher in the singlet state for both conformers.

Conclusions:

• The study validates DFT as a reliable method for studying the structural and electronic properties of iron(II) complexes.
• The observed higher electronic polarizability in the singlet state is consistent with experimental findings of a higher dielectric constant.
• These findings contribute to a deeper understanding of structure-property relationships in spin-crossover iron complexes.