Understanding Antiferromagnetic and Ligand Field Effects on Spin Crossover in a Triple-Decker Dimeric Cr(II) Complex

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Spin-crossover (SCO) behavior in metal complexes is temperature-dependent.
• Dimeric triple-decker chromium(II) complexes exhibit complex SCO phenomena.
• Existing explanations involve antiferromagnetic interactions and ligand-field effects.

Purpose of the Study:

• To computationally resolve the competing effects influencing SCO in a dimeric triple-decker Cr(II) complex.
• To elucidate the interplay between magnetic interactions and ligand-field effects on SCO transitions.
• To provide quantitative insights into the mechanisms driving temperature-dependent SCO.

Main Methods:

• Multireference electronic structure calculations.
• Multiconfiguration pair-density functional theory (MCPFT) employed.
• Analysis of electronic ground states across a temperature range.

Main Results:

• Identified quintet, triplet, and singlet ground states at high, intermediate, and low temperatures, respectively.
• Observed a quintet-to-triplet transition due to increasing antiferromagnetic interactions.
• Attributed the triplet-to-singlet transition to dominant ligand-field effects at low temperatures.

Conclusions:

• Both antiferromagnetic interactions and ligand-field effects contribute synergistically to SCO behavior.
• Ligand-field effects become dominant at lower temperatures, influencing the spin state.
• The study offers a quantitative understanding of temperature-dependent SCO mechanisms in chromium complexes.