A Diruthenium-Based Mixed Spin Complex Ru₂ ⁵⁺ (S=1/2)-CN-Ru₂ ⁵⁺ (S=3/2)

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Cyanido-bridged polynuclear complexes are of interest due to their diverse magnetic and electronic properties.
• Ruthenium-based complexes, particularly dinuclear units, offer tunable electronic structures and potential applications in catalysis and molecular magnetism.

Purpose of the Study:

• To synthesize and characterize a novel tetra-nuclear linear cyanido-bridged ruthenium complex.
• To investigate the electronic and magnetic properties of this unique mixed spin system.
• To elucidate the factors influencing the observed spin states through theoretical calculations.

Main Methods:

• Synthesis of the tetra-nuclear complex [Ru₂ (μ-ap)₄ -CN-Ru₂ (μ-ap)₄ ](BPh₄ ) (1).
• Characterization using X-ray crystallography, magnetic measurements, IR, EPR spectroscopy.
• Theoretical calculations including Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT).

Main Results:

• Complex 1 is the first reported mixed spin Ru₂ ⁵⁺ -based complex.
• Uncommon electronic configurations observed: S=1/2 for cyanido-C bound Ru₂ ⁵⁺ and S=3/2 for cyanido-N bound Ru₂ ⁵⁺ .
• Theoretical calculations reveal an increased energy gap between π* and δ* orbitals in the cyanido-C bound core due to enhanced asymmetrical π back-bonding.
• UV/Vis-NIR spectra and TDDFT calculations indicate metal-to-metal charge transfer (MMCT) from the S=3/2 to the S=1/2 ruthenium core.

Conclusions:

• The study successfully synthesized and characterized a novel tetra-nuclear ruthenium complex with unprecedented mixed spin states.
• The observed spin states are attributed to asymmetrical π back-bonding effects influencing the electronic structure of the Ru₂ ⁵⁺ cores.
• The findings provide valuable insights into the structure-property relationships in cyanido-bridged ruthenium complexes and open avenues for designing materials with tailored magnetic properties.