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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Uncovering Correlations between Structure and Valence Tautomerism in Cobalt-o-Dioxolene Crystals
Marcelo Francis Fernandes Alecrim1, Ludmila Leroy1,2, Lucas Gustavo Gonçalves Pimenta1
1Physics Department, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Belo Horizonte, Minas Gerais 31270-901, Brazil.
Summary
Pyridyl ligand torsion in cobalt-dioxolene complexes acts as a structural trigger for valence tautomerism (VTI). This geometric-electronic coupling mechanism directly influences the spin state, offering design guidelines for molecular devices.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Solid-State Physics
Background:
- Bistability in transition-metal complexes arises from phenomena like mixed valence (MV), spin-crossover (SCO), and valence tautomerism (VT).
- Valence-tautomeric interconversion (VTI) yields switchable redox isomers with potential applications in molecular devices, spintronics, and chemosensing.
- Tuning intermolecular interactions is a key strategy for modulating VTI in crystalline materials.
Purpose of the Study:
- To investigate the role of ancillary ligand torsion in cobalt-o-dioxolene complexes regarding VTI.
- To establish a direct geometric-electronic coupling mechanism controlling VTI and spin states.
- To provide design guidelines for solid-state molecular devices based on VT complexes.
Main Methods:
- Single-crystal X-ray diffraction (SCXRD) on solvated [Co-(dioxolene)2(Py)2] crystals.
- Density Functional Theory (DFT) calculations using the SIESTA package.
- Benchmarking DFT results against experimental magnetic susceptibility data using LDA functional.
Main Results:
- Torsion of pyridyl ancillary ligands in [Co-(dioxolene)2(Py)2] acts as a structural trigger for VTI, beyond metal-ligand distance changes.
- A direct geometric-electronic coupling mechanism was established, linking ligand torsion to VTI.
- DFT spin-polarization analyses showed a direct correlation between PyL plane torsion angle and the system's spin state.
Conclusions:
- Pyridyl ancillary ligand torsion is a critical factor in stabilizing electrostatic interactions and triggering VTI in cobalt-dioxolene complexes.
- The observed behavior is consistent across related trans-[Co-(dioxolene)2(PyL)2] derivatives, as evidenced by CSD data.
- These findings offer a comprehensive understanding of redox and spin-state dynamics in VT complexes, guiding future solid-state applications.
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