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Valence tautomeric transition of bis(o-dioxolene) cobalt complex in solid state and solution
A A Guda1, M Chegerev2, A G Starikov2
1The Smart Materials Research Institute, Sladkova 178/24, 344090 Rostov-on-Don, Russia.
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|February 15, 2021
Summary
Valence tautomer transitions in metal-organic complexes are key for molecular switches. This study used FTIR and XAS to analyze a cobalt complex, revealing distinct solid-state hysteresis and solution behavior.
Area of Science:
- Coordination Chemistry
- Materials Science
- Molecular Electronics
Background:
- Valence tautomer transitions in 3d metal-organic complexes with redox-active ligands are crucial for developing single-molecular switches.
- These transitions are sensitive to external stimuli (temperature, pressure, light) and intermolecular interactions.
- Limitations of single-crystal X-ray diffraction for studying such transitions in solid or solution states necessitate alternative methods.
Purpose of the Study:
- To investigate the valence tautomer transition in a bis(o-semiquinonato) cobalt complex with a TEMPO-functionalized iminopyridine ligand.
- To compare the effectiveness of Fourier transform infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS) in probing these transitions.
- To analyze the behavior of the complex in both solid and solution states.
Main Methods:
- Ligand-sensitive Fourier transform infrared spectroscopy (FTIR) was employed.
- Metal-sensitive Cobalt K-edge X-ray absorption spectroscopy (XAS) was utilized.
- The complex was studied in both solid-state and solution phases.
Main Results:
- A significant temperature hysteresis (>40 K) in magnetization was observed in the solid state, indicating a distinct phase transition upon cooling and heating.
- In solution, XAS spectra for high- and low-temperature states were comparable to the solid-state spectra, but the hysteresis was absent.
- FTIR demonstrated higher sensitivity to ligand interactions in the solid state, while XAS proved advantageous for analyzing liquid-phase transitions.
Conclusions:
- Both FTIR and XAS are effective techniques for probing valence tautomer transitions.
- The cobalt complex exhibits different transition dynamics in solid versus solution phases, with hysteresis present only in the solid state.
- XAS is particularly useful for studying valence tautomerism in solution, complementing FTIR's capabilities for solid-state analysis.
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