Robotic Stepwise Synthesis of Hetero-Multinuclear Metal Oxo Clusters as Single-Molecule Magnets

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 {FeMn 4 }Lu 2 A 2 in TBA 5 [(A-α-SiW 9 O 34 ) 2 FeMn 4 O 2 {Lu-(acac) 2 } 2 A 2 ] (II A ; A = Ag, Na, K; TBA = tetra-n-butylammonium; acac = acetylacetonate) were discovered by the installation of diamagnetic metal cations A + into a paramagnetic {FeMn 4 }Lu 2 unit in TBA 7 [(A-α-SiW 9 O 34 ) 2 FeMn 4 O 2 {Lu(acac) 2 } 2 ] (I). POMs II A exhibited single-molecule magnet properties with the higher energy barriers for magnetization reversal (II Ag , 40.0 K; II Na , 40.3 K; II K , 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.

Variable control of the electronic states of a silver nanocluster via protonation/deprotonation of polyoxometalate ligands

“…12,13 In particular, lacunary POMs can act as inorganic multidentate ligands with abundant reactive oxygen atoms. 14 We recently developed synthetic methods for atomically precise Ag nanoclusters ( e.g. , {Ag 27 } 17+ and {Ag 7 } 5+ ), which possess valence electrons and superatomic electronic states, using lacunary POMs as inorganic multidentate ligands.…”

Ligand-Protecting Strategy for the Controlled Construction of Multinuclear Copper Cores within a Ring-Shaped Polyoxometalate

“…Recently, we developed a synthesis method for well-defined multinuclear metal cores by the stoichiometric reaction of lacunary POMs and metal salts in organic solvents. For instance, we synthesized heteronuclear multimetallic oxo clusters by sequentially introducing different types of metal cations into the trivacant lacunary Keggin-type POM [SiW 9 O 34 ] 10– . In addition, organic ligands protect the coordination sites of lacunary POMs in organic solvents.…”

Supported Anionic Gold Nanoparticle Catalysts Modified Using Highly Negatively Charged Multivacant Polyoxometalates

“…However, the instability of these colloidal Au nanoparticles has limited their catalytic application, and immobilizing POM-modified Au nanoparticles on suitable supports is an inevitable and essential subject. We envisaged that multivacant lacunary POMs obtained by removing multiple metal-oxygen units, which can act as multidentate ligands for stabilizing metal-oxygen and metal clusters, [21,[23][24][25][26][27][28][32][33][34][35] are promising ligands for preparing supported anionic Au nanoparticle catalysts because they would enable further strengthening such electronic interac-tion even after immobilization on supports due to their higher negative charges and more vacant (coordination) sites (e.g., [SiW 9 O 34 ] 10À (SiW9)) than monovacant or fullyoccupied species. In particular, the oxygen atoms at the vacant sites of multivacant lacunary POMs are highly reactive and selectively coordinate to metal atoms.…”