Stabilizing Reactive Fe(III) Clusters by Freeze-Dry/Solvent-Exchange To Benchmark Iron Hydrolysis Pathways

Abstract

Isolating Fe­(III) clusters from water without stabilizing ligands is significantly challenged by the high acidity of Fe3+-bound water, leading to uncontrolled precipitation of iron oxyhydroxides. Here we demonstrate a freeze-drying solvent-exchange method that enabled the isolation of a metastable Fe­(III) sulfate decameric cluster formulated [Fe10O2(SO4)12­(OCH3)2]·14CH3OH (Fe 10 ). Without stabilization by solvent-exchange, the aqueous species undergoes rapid conversion to the iron sulfate mineral schwertmannite. Monitoring the hydrolysis process from cluster intermediates to schertmannite by small-angle X-ray scattering, we observe the progression from Fe 10 to 37 Å soluble nanoparticles prior to the precipitation process. This condensation behavior of Fe 10 is further exploited to develop a simple laboratory synthesis of schwetmannite. In addition, we demonstrate the versatility of the freeze-drying solvent-exchange method by isolating Al­(III), Zn­(II), and Cd­(II) substituted Fe­(III) sulfate clusters. The freeze-drying solvent-exchange method provides a unique opportunity to isolate cluster intermediates and models to aid in our understanding of metal-ion hydrolysis processes in environmental, material science, and geological studies.

Chiral Induction in Aluminum Oxo Sulfate Helical Chains

“…According to the CCDC database up to March 2022, there are only three cases of inorganic structures containing sulfate groups coordinated to aluminum. They are S-Al32 reported by Sun et al, 31 Al(III) substituted iron sulfate clusters reported by Nyman et al, 32 and SO 4 functionalized MOF-520 reported by Yaghi et al 33 In these structures, SO 4…”

“…According to the CCDC database up to March 2022, there are only three cases of inorganic structures containing sulfate groups coordinated to aluminum. They are S-Al32 reported by Sun et al, Al­(III) substituted iron sulfate clusters reported by Nyman et al, and SO 4 functionalized MOF-520 reported by Yaghi et al In these structures, SO 4 2– acts as appendants on Al­(III), and its role as a linker has not been explored. Our particular interest in aluminum­(III) coordination chemistry has resulted in a broad range of new structure types including high nuclearity hydrotalcite-like aluminum oxo clusters and aluminum molecular rings. − To expand applications of aluminum­(III)-based compounds in the field of chirality, we are interested in synthesizing chiral crystalline materials constructed from inorganic achiral SO 4 2– components.…”

Three in One: Three Different Molybdates Trapped in a Thiacalix[4]arene Protected Ag72 Nanocluster for Structural Transformation and Photothermal Conversion

“…[8] The molecular and electronic structures of metastable species of POMs are only substantiated by nuclear magnetic resonance, mass spectrometry, small-angle X-ray scattering and other spectroscopy techniques. [8,9] Thanks to the adjustable compositions of POMs and their high negative charges with numerous bare oxygen coordination sites, POM-templated silver nanocluster chemistry has gained remarkable progresses. [10] Different sizes, charges, and geometries of POMs can lead to diverse silver shells, which in turn act as molecular containers to trap some active POM intermediates followed by structural determinations.…”

“…Although the enormous polyoxometallates (POMs) such as Keggin, Dawson and Lindqvist structures have been determined by single crystal X‐ray diffraction (SCXRD), the atom‐precise structures of kinetically controlled intermediate species remain a black box by virtue of their fast dynamic hydrolysis‐condensation reaction in solution [8] . The molecular and electronic structures of metastable species of POMs are only substantiated by nuclear magnetic resonance, mass spectrometry, small‐angle X‐ray scattering and other spectroscopy techniques [8,9] . Thanks to the adjustable compositions of POMs and their high negative charges with numerous bare oxygen coordination sites, POM‐templated silver nanocluster chemistry has gained remarkable progresses [10] .…”