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Spin-crossover behaviors in solvated cobalt(ii) compounds.
Shinya Hayami1, Manabu Nakaya, Hitomi Ohmagari
1Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan. hayami@sci.kumamoto-u.ac.jp.
Two cobalt(ii) terpyridine complexes were synthesized and annealed to form desolvated species. These species exhibit distinct spin crossover behaviors, with one showing a two-step transition and the other a gradual transition.
Area of Science:
- Coordination Chemistry
- Materials Science
- Physical Chemistry
Background:
- Cobalt(ii) terpyridine complexes are known for their potential in spin crossover (SCO) applications.
- Solvation and desolvation processes can significantly influence the SCO properties of metal complexes.
- Understanding these effects is crucial for designing materials with tunable magnetic properties.
Purpose of the Study:
- To synthesize and characterize two novel solvated cobalt(ii) terpyridine complexes.
- To investigate the spin crossover (SCO) behavior of desolvated species derived from these complexes.
- To explore the impact of solvent molecules on the SCO properties and phase transitions.
Main Methods:
- Synthesis of solvated cobalt(ii) terpyridine complexes: [Co(MeO-terpy)2](BF4)2·H2O and [Co(MeO-terpy)2](BF4)2·acetone.
- Annealing of solvated complexes to form desolvated species.
- Variable-temperature magnetic susceptibility measurements to study spin crossover (SCO).
Main Results:
- The solvated complexes yielded two desolvated species upon annealing.
- One desolvated species exhibited a two-step spin crossover (SCO).
- The other desolvated species displayed a gradual SCO and a high-spin state across all temperatures, with a reverse spin transition linked to a phase change.
Conclusions:
- The presence and type of solvent molecules in cobalt(ii) terpyridine complexes significantly influence the SCO behavior of their desolvated counterparts.
- Desolvation can lead to distinct SCO mechanisms, including two-step and gradual transitions.
- Phase transitions in desolvated complexes can induce reverse spin transitions, offering pathways for material design.
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