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Valence tautomerism in a cobalt-verdazyl coordination compound
Connor Fleming1, Dorothy Chung1, Servando Ponce1
1Department of Chemistry, San Jose State University, One Washington Square, San Jose, CA 95126, USA. david.brook@sjsu.edu.
Chemical Communications (Cambridge, England)
|April 4, 2020
Summary
Cobalt coordination complexes with radical ligands exhibit distinct electronic structures in solid and solution states. The dication transitions from cobalt(II) with radical ligands to cobalt(III) valence tautomers upon dissolution.
Area of Science:
- Inorganic Chemistry
- Coordination Chemistry
- Spin Crossover Materials
Background:
- Verdazyl radicals are known ligands in coordination chemistry.
- Cobalt complexes can exhibit diverse spin states and redox properties.
Purpose of the Study:
- To investigate the coordination of a specific verdazyl radical ligand to cobalt.
- To characterize the electronic structure and spin state of the resulting complex in different phases.
Main Methods:
- Single crystal X-ray diffraction for solid-state analysis.
- Solution-state spectroscopic and magnetic susceptibility measurements.
- Computational modeling to support electronic structure assignments.
Main Results:
- The solid-state structure reveals a high-spin cobalt(II) ion coordinated to two radical ligands (S = 3/2).
- In acetonitrile solution, an equilibrium is established with a cobalt(III) valence tautomer (S = 1/2).
- This indicates a reversible valence tautomerization driven by the solvent environment.
Conclusions:
- The cobalt-verdazyl system demonstrates a unique solid-state to solution-state transformation.
- The observed spin crossover behavior is sensitive to the coordination environment and solvent polarity.
- This study highlights the potential for designing switchable molecular materials based on valence tautomerism.
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