First Tungstoantimonate-Based Transition-Metal–Lanthanide Heterometallic Hybrids Functionalized by Amino Acid Ligands

Abstract

By the routine aqueous solution method, a series of transitionmetal−lanthanide heterometallic tungstoantimonates [Ln(H 2 O) 8 ] 2 -[Fe 4 (H 2 O) 8 (thr) 2 ][B-β-SbW 9 O 33 ] 2 ·22H 2 O [Ln = Pr III (1), Nd III (2), Sm III (3), Eu III (4), Gd III (5), Dy III (6), Lu III (7), thr = threonine] were prepared and structurally characterized by multiple testing techniques. The common structural characteristic of 1−7 is that they are isomorphous and all consist of a [Fe 4 (H 2 O) 8 (thr) 2 (B-β-SbW 9 O 33 ) 2 ] 6− subunit with two supporting [Ln(H 2 O) 8 ] 3+ cations on both sides. It should be pointed out that two thr ligands in the [Fe 4 (H 2 O) 8 (thr) 2 (B-β-SbW 9 O 33 ) 2 ] 6− subunit substitute for two water ligands in the classical [Fe 4 (H 2 O) 10 (B-β-SbW 9 O 33 ) 2 ] 6− polyoxoanion. As far as we know, 1−7 represents the first organic−inorganic tungstoantimonate hybrids consisting of transition metal and lanthanide cations and amino acid components. The fluorescence behavior of 4 has been measured and manifests the remarkable fluorescence feature resulting from the emission signature of Eu III cations. Furthermore, the solid-state electrochemistry and electrocatalytic performances of 1 have been measured in 0.5 mol L −1 Na 2 SO 4 +H 2 SO 4 aqueous solution, and the results show that 1 illustrates comparatively apparent catalytic activities toward the BrO 3 − and H 2 O 2 reduction. The magnetic properties of 3 and 6 have been studied. ■ INTRODUCTION Polyoxometalates (POMs) represent an special family of intriguing metal−oxygen cluster compounds formed by high oxidation state early transition metals (preferably Mo, W, V, and Nb) bearing tremendous diverse structures, seductive properties, and latent applications in catalysis, magnetism, electronics, photoluminescence, pharmaceutical, and materials science. 1−9 Highly negative charge, O-enriched lacunary POMs, can act as one kind of outstanding multidentate nucleophilic candidates to coordinate to transition-metal (TM) or lanthanoid (Ln) ions to construct neoteric TM or Ln encapsulated POM aggregates with varying metal centers, alluring topological architectures and novel properties, which can also make more magnetic or catalytic components implant to the POM cluster skeletons. Therefore, the exploration and discovery of TM-or Ln-functionalized POMs have attracted considerable interest over the past few decades. Hitherto, a vast amount of TM-or Ln-substituted POMs have been sequentially discovered. 10−19 In contrast, explorations on POM-based TM−Ln heterometallic derivatives (PTLHDs) still remain less developed, although their unmatched diversities and physicochemical properties entail them to become candidates for magnetic materials or optical sensing materials. 20−22 Less work dedicated to PTLHDs mainly lies in an inescapable competing reaction between electrophilic Ln and TM cations with nucleophilic POM precursors within a system. 23 Therefore, the search and preparation of POMbased TM−Ln heterometallic materials will remain a longstanding and persisting chall...

Synthesis, structure and electrochemical properties of a Fe III –Ce III heterometallic sandwich-type tungstoantimonate with novel 2-D infinite structure [Ce(H 2 O) 8 ][Ce(H 2 O) 6 ][Fe 4 (H 2 O) 10 (B-β-SbW 9 O 33 ) 2 ]·16H 2 O

“…3d). These results indicate that the reduction procedures of BrO 3 − and NO 2 − are mainly controlled by the reduced species of tungsten-oxo clusters in 1, which is in good consistence with the previous results [2,37]. More specific catalytic efficiencies (CATs) are accurately evaluated through Keita's method (Table S1).…”

“…1c) must have happened. Such isomerization phenomenon has been observed in previous research of TAs [2,[27][28][29].…”

“…As shown in Fig. 3a, two pairs of redox waves with E 1/2 = −0.568 V (I/I′) and E 1/2 = −0.146 V (II/II′) [E 1/2 = (E pa + E pc )/2, vs SCE electrode] in the negative potential [2]. Moreover, their peak potential separations (ΔE p ) of the W VI -based waves are around 102 mV and 73 mV, which demonstrate the quasi-reversible one-electron charge-transfer redox procedure of W VI centers in the POA frameworks.…”

“…The electrochemical and electrocatalytic properties of 1 have been systemically studied in 0.5 mol·L −1 Na 2 SO 4 + H 2 SO 4 supporting electrolyte, moreover, 1 exhibits the obvious electrocatalytic activity towards the reduction of BrO 3 − and NO 2 − . © 2015 Elsevier B.V. All rights reserved.With the specific oxygen-enriched surfaces, controllable sizes and high negative charges, lacunary polyoxometalate (POM) precursors are often selected as benign multidentate inorganic ligands to integrate oxophilic transition-metal (TM) or rare-earth (RE) cations into a great number of functional mental-oxo clusters in various fields such as catalysis, magnetism, photochemistry, medicine and materials science [1][2][3][4][5]. In the past several decades, numerous TM-substituted POMs (TMSPs) and RE-substituted POMs (RESPs) with neoteric structures have been dug out because of the extensive use of this assembly strategy of POM precursors.…”

Diverse Ligand‐Functionalized Mixed‐Valent Hexamanganese Sandwiched Silicotungstates with Single‐Molecule Magnet Behavior

“…[20] Moreover,P OM-based supramolecular architectures are among the most promising materials in the fields of chemicobiology,m aterials chemistry,a nd so on. [21] In this respect, 3D supramolecular structures also exist in 1-6.I nt he structure of 1,t he Na toms of deta ligandsf unctioning as protond onors participate in the formation of NÀH···Oi nteractions with the surfaceOatoms of [B-a-SiW 9 O 34 ] 10À fragments serving as proton acceptors.S pecifically,a djacent 1a units are interconnected by NÀH···Oi nteractions with amino groups of free deta ligandst of orm a1 Ds upramolecular chain along the a axis ( Figure S4 in the Supporting Information). Furthermore, neighboring chains are connected with each other to give a3 D supramolecular framework (Figure 1d), in whiche ach 1a unit acts as at en-connected node.…”