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Ligand Modifications Produce Two-Step Magnetic Switching in a Cobalt(dioxolene) Complex
Khadanand Kc1, Toby Woods2, Lisa Olshansky1
1Department of Chemistry, Center for Biophysics and Quantitative Biology, Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois, 61801, USA.
Angewandte Chemie (International Ed. in English)
|September 21, 2023
Summary
Researchers developed a new cobalt complex with a modified ligand, enabling two-step magnetic switching. This breakthrough offers a third magnetic state and potential for advanced molecular switches.
Area of Science:
- Coordination Chemistry
- Materials Science
- Molecular Magnetism
Background:
- Mononuclear cobalt complexes with monodioxolene ligands exhibit valence tautomerism (VT) between low-spin (l.s.) CoIII (catecholato) and high-spin (h.s.) CoII (seminquinonato) states.
- The tetradentate ligand framework typically supports these states, influencing the temperature of the VT transition.
- Accessing intermediate magnetic states in these systems is challenging.
Purpose of the Study:
- To investigate the effect of ligand modification on the magnetic properties of mononuclear monodioxolene cobalt complexes.
- To explore the possibility of accessing new magnetic states beyond typical valence tautomerism.
- To develop novel multi-state molecular switches.
Main Methods:
- Synthesis and characterization of novel cobalt complexes featuring a modified tetradentate ligand (tris(2-pyridylmethyl)amine with an ortho-anisole moiety).
- Variable temperature crystallographic, magnetic, calorimetric, and spectroscopic studies.
- Analysis of electron transfer and spin crossover phenomena.
Main Results:
- A third magnetic state, consistent with l.s. CoII (seminquinonato), was accessed by modifying the ligand.
- The modified complex exhibits a two-step magnetic switching behavior: VT from l.s. CoIII (catecholato) to l.s. CoII (seminquinonato), followed by spin crossover from l.s. CoII (seminquinonato) to h.s. CoII (seminquinonato).
- This represents the first observation of two-step magnetic switching in a mononuclear monodioxolene cobalt complex.
Conclusions:
- Ligand design, specifically incorporating flexibility or weaker field moieties, can facilitate access to rarely observed intermediate magnetic states.
- The observed two-step magnetic switching behavior highlights a new pathway for creating advanced stimulus-responsive molecular switches.
- Ligand dynamicity is proposed as a key factor in accessing the l.s. CoII state, suggesting a new design criterion for molecular switches.
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