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

Abstract

The assembly of gigantic heterometallic metal clusters remains a great challenge for synthetic chemistry. Herein, based on the slow release strategy of lanthanide ions and in situ formation of lacunary polyoxometalates, two giant 3d‐4f polyoxometalate inorganic clusters [LaNi12W35Sb3P3O139(OH)6]23− (LaNi12) and [La10Ni48W140Sb16P12O568(OH)24(H2O)20]86− (La10Ni48) are obtained. The nanoscopic inorganic cluster La10Ni48 possesses a super tetrahedron structure, which can be viewed as assembly from four LaNi12 molecules encapsulating a central [La6(SbO3)4(H2O)20]6+ octahedron core. This giant aesthetic La10Ni48 tetrahedron containing 214 metal ions is the largest 3d‐4f cluster reported thus far in polyoxometalate system. More interestingly, the LaNi12 and La10Ni48 display high stability in solution and La10Ni48 displays excellent proton conductivity.

Snapshots of Ce70 Toroid Assembly from Solids and Solution

“…Such synthetic approaches are essential for optimizing materials function, including catalysis, 13 magnetism, [14][15][16][17][18] and luminescence. [19][20] Building-block synthetic approaches have been hypothesized in metal-oxo systems including; 1) assembly of Pd84 and Pd72 Pd-oxo toroids from a Pd6 fragment; [21][22][23] 2) Mn84 and Mn70 built from a Mn12 oxo-acetate; [24][25] 3) growth of giant molybdate POMs from smaller clusters; 26-27 4) assembly of successively larger Lnx species (x = 12-140) from a Ln4 oxocluster building unit; 18,[28][29][30][31] , 5) isolation of various sized LnxNiyoxoclusters (up to 164 metal polyhedra) from smaller oxocluster building blocks, 15,[32][33] and 6) capping and linking of POMs into rigid chains and frameworks, and flexible polymers. [34][35][36] The d-block and f-block tetravalent metal cations (M IV =Zr/Hf/Ce/U/Np/Pu IV ) are amongst the most studied metal-oxo cluster families.…”

“…Metal-oxo clusters (including polyoxometalates, POMs), which can be viewed as molecular metal-oxides, have greatly aided our ability to design purely inorganic materials with molecular-level precision. Such synthetic approaches are essential for optimizing materials function, including catalysis, magnetism, − and luminescence. , Building-block synthetic approaches have been hypothesized in metal-oxo systems including (1) assembly of Pd 84 and Pd 72 Pd-oxo toroids from a Pd 6 fragment, − (2) Mn 84 and Mn 70 built from a Mn 12 oxo-acetate, , (3) growth of giant molybdate POMs from smaller clusters, , (4) assembly of successively larger Ln x species (x = 12–140) from a Ln 4 oxocluster building unit, ,− (5) isolation of various sized Ln x Ni y -oxoclusters (up to 164 metal polyhedra) from smaller oxocluster building blocks, ,, and (6) capping and linking of POMs into rigid chains and frameworks, and flexible polymers. − …”

Snapshots of Ce70 Toroid Assembly from Solids and Solution

“…Such synthetic approaches are essential for optimizing materials function, including catalysis, 13 magnetism, [14][15][16][17][18] and luminescence. [19][20] Building-block synthetic approaches have been hypothesized in metal-oxo systems including; 1) assembly of Pd84 and Pd72 Pd-oxo toroids from a Pd6 fragment; [21][22][23] 2) Mn84 and Mn70 built from a Mn12 oxo-acetate; [24][25] 3) growth of giant molybdate POMs from smaller clusters; 26-27 4) assembly of successively larger Lnx species (x = 12-140) from a Ln4 oxocluster building unit; 18,[28][29][30][31] , 5) isolation of various sized LnxNiyoxoclusters (up to 164 metal polyhedra) from smaller oxocluster building blocks, 15,[32][33] and 6) capping and linking of POMs into rigid chains and frameworks, and flexible polymers. [34][35][36] The d-block and f-block tetravalent metal cations (M IV =Zr/Hf/Ce/U/Np/Pu IV ) are amongst the most studied metal-oxo cluster families.…”

Organoamine-Directed Assembly of 5p–4f Heterometallic Cluster Substituted Polyoxometalates: Luminescence and Proton Conduction Properties

“…Finally, the activation energy is calculated according to the Arrhenius equation (σ T = σ 0 exp­(− E a / k B T )). The E a at 98% RH for 1-Ce was calculated to be 0.34 eV (Figure e), suggesting that the conduction proceeds by the Grotthuss mechanism, given that the activation energy is in the range of 0.1–0.4 eV. − This may be ascribed to the presence of discrete protonated [H 2 en] 2+ cations interacting with some lattice water molecules and polyoxyanions to form a hydrogen bond network. With the temperature rising, the water movement and the vibration frequency of the N–H bond are accelerated, which promote the hopping of protons in the hydrogen-bond network and thus improve the proton conductivity .…”