Synthesis of a 6-nm-Long Transition-Metal–Rare-Earth-Containing Polyoxometalate

Abstract

An extremely long ribbon-shaped polyoxometalate (POM) octamer, {Eu16­Co7­Se16­W128­O448­(CIT)10­(HCIT)2­(NO3)4­(OH)4­(H2O)52} (H4CIT = citric acid), with a maximum length of ca. 6 nm has been obtained, which is the longest molecular POM reported to date and the first Dawson-based 3d–4f-containing selenotungstate­(IV). The nanoscale octamer is built from 8 new Dawson-type Eu2W2-substituted selenotungstates {(Eu2W2O4)­Se2W14O52} bridged by 12 H4CIT ligands and 3 Co2+ ions, giving rise to a rare giant inorganic–organic hybrid molecular POM with more than 150 metal centers (7 CoII, 16 EuIII, 16 SeIV, and 128 WVI). Especially, with 128 W centers and more than 800 non-H atoms, the POM octamer also represents the largest known 3d–4f-containing polyoxotungstate.

Organobor‐Funktionalisierung ermöglicht die hierarchische Aggregation gigantischer Polyoxometallat‐Nanokapseln

“…POMs sind ideale Modelle für die Aggregation in größere Nanostrukturen, da bereits eine Anzahl von POM‐Verknüpfungskonzepten etabliert wurden: Derzeit wird das Feld durch die Metall‐Kation‐Verknüpfung von POMs dominiert, meist werden dazu Übergangsmetall‐ oder Lanthanidverknüpfungen eingesetzt . Meist werden dazu Wolframate vom Keggin‐ und Dawson‐Typ oder deren Derivate verwendet, um so gigantische “Cluster‐of‐Cluster”‐Strukturen oder sogar POM‐basierte offene Gerüste zu erzeugen …”

A Giant 3d‐4f Polyoxometalate Super‐Tetrahedron with High Proton Conductivity

“…In comparison, the inorganic anions with multisite coordination geometry can obviously improve the stability. [ 16–40 ]…”

“…The polyoxometalates (POMs) are a type of early transitional metal‐oxygen clusters, the physical and chemical characteristics of which, such as low effective surface charge density, high thermal stability, electron‐accepting capability, and, in particular, discrete mobile ionic constituents, and “pseudoliquid phase” behavior, are especially suitable for use as proton conductors. [ 41–50 ] Among them, the lacunary POMs have high nucleophilicity and high reactivity, [ 8,16–40 ] which can be used to stabilize polynuclear metal clusters into cluster‐of‐cluster aggregates. To data, only limited high‐nuclearity transition metal clusters stabilized by lacunary POMs have been obtained, such as [Cu 20 W 48 ], [ 19 ] [Ni 25 W 54 ], [ 20 ] [Fe 28 W 48 ], [ 21 ] [Co 16 W 36 ], [ 22,23 ] [Ti 16 W 60 ], [ 24 ] [Zr 24 W 52 ], [ 25 ] and [Mn 19 W 60 ].…”

Synthesis, Characterization, Electrochemistry, Photoluminescence and Magnetic Properties of a Dinuclear Erbium(III)-Containing Monolacunary Dawson-Type Tungstophosphate: [{Er(H2O)(CH3COO)(P2W17O61)}2]16−

“…Focusing only on Ln-containing POMs (Ln-POMs); lacunary POMs with nucleophilic oxygen centers are ideal multidentate ligands for lanthanide ions owing to their high oxophilic nature. In addition, Ln ions can have high coordination numbers, thus they can link POM building blocks to create discrete giant Ln-POM structures or polymeric networks (1D, 2D and 3D extended POMs) [ 6 , 7 , 8 , 9 , 10 ]. However, in Ln-POMs due to their larger sizes and consequently larger coordination numbers compared to 3d metal ions, the formation of lanthanide-oxo-hydroxo clusters within the POM framework has been rarely observed [ 9 , 11 , 12 ].…”