Abstract
An efficient stepwise synthesis method for discovering new heteromultinuclear metal clusters using a robotic workflow is developed where numerous reaction conditions for constructing heteromultinuclear metal oxo clusters in polyoxometalates (POMs) were explored using a custom-built automated platform. As a result, new nonanuclear tetrametallic oxo clusters {FeMn4}Lu2A2 in TBA5[(A-α-SiW9O34)2FeMn4O2{Lu(acac)2}2A2] (IIA; A = Ag, Na, K; TBA = tetra-n-butylammonium; acac = acetylacetonate) were discovered by the installation of diamagnetic metal cations A+ into a paramagnetic {FeMn4}Lu2 unit in TBA7[(A-α-SiW9O34)2FeMn4O2{Lu(acac)2}2] (I). POMs IIA exhibited single-molecule magnet properties with the higher energy barriers for magnetization reversal (IIAg, 40.0 K; IINa, 40.3 K; IIK, 26.7 K) compared with that of the parent I (19.7 K). Importantly, these clusters with unique properties were constructed as designed by a step of the predictable sequential multistep reactions with the time-efficient platform.
Highlights
Over the past several decades, material scientists have tried to develop effective methods in response to the scientifically inspirational question posed by Richard P
We have successfully synthesized heteromultinuclear metal oxo clusters possessing a wide variety of metal cations using lacunary POMs.9a−e In these reports, arranging the proper types of metal cations in the desired position was demonstrated by the stepwise synthesis method, showing the precise control of their coordination geometries and magnetic properties
To demonstrate the efficient robotic stepwise synthesis method, a system of heteromultinuclear metal oxo clusters within trivacant lacunary POMs is chosen in this study because the above-mentioned three tasks can systematically be examined
Summary
Over the past several decades, material scientists have tried to develop effective methods in response to the scientifically inspirational question posed by Richard P. Polyoxometalates (POMs) are a family of anionic molecular metal oxide clusters that exhibit diversity of structures, sizes, and physical and chemical properties.[7] By utilizing lacunary POMs as robust, bulky multidentate inorganic ligands, numerous types of multinuclear metal and metal oxo clusters possessing unique catalytic, electronic, and magnetic properties have been synthesized.[8,9] Recently, we have successfully synthesized heteromultinuclear metal oxo clusters possessing a wide variety of metal cations using lacunary POMs.9a−e In these reports, arranging the proper types of metal cations in the desired position was demonstrated by the stepwise synthesis method, showing the precise control of their coordination geometries and magnetic properties These results indicated that lacunary POMs act as ideal multidentate ligands for constructing various types of heteromultinuclear metal clusters by a predictable stepwise synthesis method. This facilitated the discovery of three new singlemolecule magnets (SMMs) including the structure with the highest energy barrier for magnetization reversal (Ueff) among the previously reported transition metal-containing POMs
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