Water-Stable Manganese(IV) Complex of a N<sub>2</sub>O<sub>4</sub>‑Donor Non-Schiff-Base Ligand: Synthesis, Structure,
and Multifrequency High-Field Electron Paramagnetic Resonance Studies
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Abstract
A novel water-stable (<i>t</i><sub>1/2</sub> ∼
6.8 days) mononuclear manganese(IV) complex of a hexacoordinating
non-Schiff-base ligand (H<sub>4</sub>L) with N<sub>2</sub>O<sub>4</sub>-donor atoms has been synthesized and characterized crystallographically.
High-frequency electron paramagnetic resonance experiments performed
on a single crystal reveal a manganese(IV) ion with an <i>S</i> = <sup>3</sup>/<sub>2</sub> ground spin state that displays a large
single-ion anisotropy, setting the record of mononuclear manganese(IV)
complexes reported so far. In addition, spin–echo experiments
reveal a spin–spin relaxation time <i>T</i><sub>2</sub> ∼ 500 ns
