A cubic Fe4Mo4 oxo framework and its reversible four-electron redox chemistry

Investigation of Cubic Fe4 M4 Frameworks for Application in Nonaqueous Energy Storage

Multimetallic complexes have recently seen increased attention as next-generation charge carriers for nonaqueous redox flow batteries. Herein, we report the electrochemical performance of a molecular iron-molybdenum oxido complex, {[(Me₃ TACN)Fe][μ-(MoO₄ κ³ O,O',O")]}₄ (Fe₄ Mo₄ O₁₆ ). In symmetric battery charging schematics, Fe₄ Mo₄ O₁₆ facilitates reversible two-electron storage with coulombic efficiencies >99 % over 100 cycles (5 days) with no molecular decomposition and minimal capacity fade. Energy efficiency throughout cycling remained high (∼82 %), as a result of the rapid electron-transfer kinetics observed for each of the complex's four redox events. We also report the synthesis of the analogous synthetic frameworks featuring tungstate vertices or bridging-sulfide moieties, revealing key observations relevant to structure-function relationships and design criteria for these types of heterometallic ensembles.

Iron molybdenum nitrilotriacetate and iminodiacetate – spectroscopy, structural characterization and CO2 adsorption

The tetranuclear iron molybdate Na₆[(MoO₂)₂O₂Fe₂(nta)₄]·16H₂O (1) and its isomorphous complexes form 2D water layer structures in a modular manner, and a decanuclear heterometallic polymer, [(MoO₄)₂FeII4FeIII4(ida)₈]_n (2), contains an interesting cubic 3D microporous structure with a 3.3 Å diameter hole and can adsorb a small amount of CO₂.