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Interactive Molecular Model Assembly with 3D Printing
Published on: August 13, 2020
pH-Driven Rotational Configuration of Keggin-Fe13 Clusters and Their Transformations
Man-Ting Chen1, Qiao-Fei Xu1, La-Sheng Long1
1State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Abstract:
Keggin-Fe13 clusters are considered foundational building blocks or prenucleation precursors of ferrihydrite. Understanding the factors that influence the rotational configuration of these clusters, and their transformations in water, is vital for comprehending the formation mechanism of ferrihydrite. Here, we report syntheses and crystal structures of four lanthanide-iron-oxo clusters, namely, [Dy6Fe13(Gly)12(μ2-OH)6(μ3-OH)18(μ4-O)4(H2O)17]·13ClO4·19H2O (1), [Dy6Fe13(Gly)12(μ3-OH)24(μ4-O)4(H2O)18]·13ClO4·14H2O (2), [Pr8Fe34(Gly)24(μ3-OH)28(μ3-O)30(μ4-O)4(H2O)30]·6ClO4·20H2O (3), and [Pr6Fe13(Gly)12(μ3-OH)24(μ4-O)4(H2O)18]·13ClO4·22H2O (4, Gly = glycine). Single-crystal analyses reveal that 1 has a β-Keggin-Fe13 cluster, marking the first documented instance of such a cluster to date. Conversely, both 2 and 4 contain an α-Keggin-Fe13 cluster, while 3 is characterized by four hexavacant ε-Keggin-Fe13 clusters. Magnetic property investigations of 1 and 2 show that 2 exhibits ferromagnetic interactions, while 1 exhibits antiferromagnetic interactions. An exploration of the synthetic conditions for 1 and 2 indicates that a higher pH promotes the formation of α-Keggin-Fe13 clusters, while a lower pH favors β-Keggin-Fe13 clusters. A detailed analysis of the transition from 3 to 4 emphasizes that lacunary Keggin-Fe13 clusters can morph into Keggin-Fe13 clusters with a decrease in pH, accompanied by a significant change in their rotational configuration.
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