Giant Hollow Heterometallic Polyoxoniobates with Sodalite‐Type Lanthanide–Tungsten–Oxide Cages: Discrete Nanoclusters and Extended Frameworks

Abstract

The first series of niobium–tungsten–lanthanide (Nb‐W‐Ln) heterometallic polyoxometalates {Ln12W12O36(H2O)24(Nb6O19)12} (Ln=Y, La, Sm, Eu, Yb) have been obtained, which are comprised of giant cluster‐in‐cluster‐like ({Ln12W12}‐in‐{Nb72}) structures built from 12 hexaniobate {Nb6O19} clusters gathered together by a rare 24‐nuclearity sodalite‐type heterometal–oxide cage {Ln12W12O36(H2O)24}. The Nb‐W‐Ln clusters present the largest multi‐metal polyoxoniobates and a series of rare high‐nuclearity 4d‐5d‐4f multicomponent clusters. Furthermore, the giant Nb‐W‐Ln clusters may be isolated as discrete inorganic alkali salts and can be used as building blocks to form high‐dimensional inorganic–organic hybrid frameworks.

Recent advances in polyoxometalate-based lanthanide–oxo clusters

“…The reported POMs-based LnOCs involve polyoxotungstates, polyoxoniobates, polyoxomolybdates, etc. [42][43][44]. Here we summarize the polyoxotungstates-related LnOCs, which can be classified into three main categories based on the inner metal species of the cluster: pure 4f clusters, d-4f clusters, and p-4f clusters.…”

Three Types of Lanthanide-Containing Polyoxoniobates and Their Luminescence Properties

“…In compound I-Ce, the nine-coordinated Ce1 3+ ion bonds to three μ 3 -O atoms (O2 and O3 atoms from the peroxo group bond of {NbO 7 } pseudo-octahedra, Ce1−O2: 2.518(9) Å, Ce1−O3: 2.621 (10) 11)), finishing a distorted-crown-square-antiprismatic geometry with the O4W atom occupying the cap site (Figure 1b).…”

“…At present, the main solutions for synthesizing PONbs-based Ln derivatives are as follows: (1) In acidic systems, the precursor potassium hexaniobate (Nb 6 ) is protected by hydrogen peroxide and then reacts with Ln 3+ ions; 7 (2) organic carboxylic acid is used to complex with Nb 6 and Ln 3+ ions, providing the possibility for them to react under neutral or even acidic conditions; 8 (3) in the alkaline system, Ln 3+ ions first combine with ligands with strong chelating ability, such as [H 2 edta]Na 2 •2H 2 O, and then react with Nb 6 ; 9 (4) synthesis by the hydrothermal method. 10 Recently, several peroxopolyoxoniobate clusters were designed and synthesized by introducing heteroatoms under acidic conditions in the presence of H }. 11 In addition, a series of transition metal/Ln derivatives of {Nb 6 P 4 O 24 (O 2 ) 6 } clusters were synthesized.…”

“…The PSeNb 3 fragment can be viewed as a {Nb 3 O 10 (O 2 ) 3 } fragment based on a triangular arrangement of three edge-sharing {NbO 7 } units that capture a {SeO 3 } group and a {PO 4 } group. Every niobium atom represents a pentagonal bipyramid geometry via four μ 2 -O atoms, one μ 3 -O atom, and one peroxo group, and the Nb−O bond lengths range from 1.800 (10) to 2.207(10) Å (Figure S2). The selenium atom in the tri-coordinated triangular cone configuration is located at the cap position of P 2 Se 2 Nb 6 (Se−O, 1.672(10)−1.718(10) Å), while the "belt" phosphorus atom exhibits tetrahedral geometry (P−O, 1.497(10)− 1.552(10) Å).…”

A Chromium-Substituted Polyoxoniobate with High Ionic Conductivity

“…Some representative examples include Ti-containing PONbs {Ti 12 Nb 6 }, {TiNb 9 }, and {Ti 2 Nb 8 }, 6 Mn-containing PONb {MnNb 9 }, 7 Co-containing PONbs {Co 14 Nb 56 } and {Co 8 Nb 24 }, 8 Cu-containing PONbs {Cu 24 Nb 56 } and {Cu 25.5 Nb 56 }, 9 and the largest heterometal-containing PONbs {Ln 12 W 12 Nb 72 } (Ln = Y, La, Sm, Eu, Yb). 10 Recently, Niu, Wang, and co-workers also reported a new Fe-containing PONb, {Fe 3 Nb 25 }, and a new Lncontaining PONb, {Eu 3 Nb 48 }. 11 Nevertheless, the integration of TMs and PONbs is challenging, and known TM-containing PONbs are still limited because of the strong basic reaction conditions (usually >10) required for the dissolution of starting niobate species, under which most TM ions easily precipitate as hydroxides, especially for relatively highly charged (>2+) metal ions.…”