A Cationic Metal Glue Strategy for Expanding Paramagnetic Hetero-Multinuclear Metal-Oxo Clusters within Polyoxometalate Ligands

Precise structural design of large hetero-multinuclear metal-oxo clusters is crucial for controlling their large spin ground states and multielectron redox properties for application as a single-molecule magnet (SMM), molecular magnetic refrigeration, and efficient redox catalyst. However, it is difficult to synthesize large hetero-multinuclear metal oxo clusters as designed because the final structures are unpredictable when employing conventional one-step condensation reaction of metal cations and ligands. Herein, we report a "cationic metal glue strategy" for increasing the size and nuclearity of hetero-multinuclear metal-oxo clusters by using lacunary-type anionic molecular metal oxides (polyoxometalates, POMs) as rigid multidentate ligands. The employed method enabled the synthesis of {(FeMn4 )Mn2 Ln2 (FeMn4 )} oxo clusters (Ln=Gd, Tb, Dy, and Lu), which are the largest among previously reported paramagnetic hetero-multinuclear metal-oxo clusters in POMs and showed unique SMM properties. These clusters were synthesized by conjugating {FeMn4 } oxo clusters with Mn and Ln cations as glues in a predictable way, indicating that the "cationic metal glue strategy" would be a powerful tool to construct desired large hetero-multinuclear metal clusters precisely and effectively.

Cu/Ag Complex Modified Keggin-Type Coordination Polymers for Improved Electrochemical Capacitance, Dual-Function Electrocatalysis, and Sensing Performance

Different metal-organic units were introduced into the {PMo₁₂} polyoxometalate (POM) system to yield three porous coordination polymers with distinct characteristics, {Cu(pra)₂}[{Cu(pra)₂}₃{PMo₁₁^VIMo^VO₄₀}] (1), [{Ag₅(pz)₆(H₂O)_0.5Cl}{PMo₁₁^VIMo^VO₄₀}] (2), and [{Cu₃(bpz)₅(H₂O)}{PMo₁₂O₄₀}] (3) (pra = pyrazole; pz = pyrazine; bpz = benzopyrazine), via an in situ hydrothermal method. In comparison with the maternal Keggin cluster and most reported POM electrode materials, compounds 1-3 exhibit larger specific capacitances (672.2, 782.1, and 765.2 F g^-1 at a current density of 2.4 A g^-1, respectively), superior cyclic stability (91.5%, 89.3%, and 87.8% of cycle efficiency after 5000 cycles, respectively), and boosted conductivity, which may be attributed to the introduction of metal-organic units. The result indicates that metal-organic units can effectively enhance the capacitance performance of POMs. This may be due to the fact that they provide additional redox centers, induce the formation of stable porous structures, and improve ion/electron transfer efficiency. Compounds 1-3 present excellent electrocatalytic activity in reducing peroxide (H₂O₂) and oxidizing ascorbic acid (AA). In addition, compound 2 shows an outstanding sensing performance detection of AA and H₂O₂.

Self-assembly and lithium storage performance of a nanoscale polyoxometalate based on the {MnTa18} cluster

A nanosized Ta/W mixed addendum polyoxometalate (Cs12K3H7[MnTa18Si6W54O231]·61H2O) based on the unprecedented {MnTa18} cluster was fabricated successfully under hydrothermal conditions. An excellent electrochemical performance of this compound was found in lithium-ion batteries (LIBs) as an anode material. The discharge capacity was 829.9 mA h g-1 at a current density of 100 mA g-1 in the first cycle and stable at 428.4 mA h g-1 after 100 cycles, which suggests the potential application of this new compound in LIBs.