Self‐Assembly of Nanometer‐Scale [Cu₂₄I₁₀L₁₂]¹⁴⁺ Cages and Ball‐Shaped Keggin Clusters into a (4,12)‐Connected 3D Framework with Photoluminescent and Electrochemical Properties

Abstract

The design and construction of coordination polymers from preformed metal clusters, [1] such as metal carboxylate clusters [2] and chalcogenide supertetrahedral clusters, [3] to produce new materials with unique properties have been the focus of recent research interest. However, given the importance of cuprous iodide clusters in photochemistry and photophysics, [4] as well as their considerable variety of structural forms not encountered for other iodometalates, [5] it is surprising that relatively little progress has been made in using them as building blocks for the fabrication of multidimensional coordination frameworks.[6] On the other hand, polyoxometalates (POMs), [7,8] as a unique class of metaloxide clusters, have many properties that make them attractive for applications in catalysis, biology, magnetism, optics, and medicine.[9] Impressive studies on linking of these welldefined metal-oxygen building blocks to generate giant discrete clusters and related extended structures have been performed. [10,11] However, up to now no reports have been made on the combination of these two interesting fields to prepare high-dimensional cluster-based compounds, although POM chemistry has touched an almost unprecedented number of other fields of chemistry.[9b] Such composite materials present the opportunity to generate high-dimensional nanoscopic assemblies from even larger multinanounits and also have vast potential for use in materials science by incorporation of their own physical and chemical properties.Among the many different types of POMs, we chose the Keggin heteropolyanions, as they are the most widely recognized and thoroughly studied. Furthermore, we used the N-heterocyclic ligand 4-[3-(1H-1,2,4-triazol-1-yl)propyl]-4H-1,2,4-triazole (L, see the Supporting Information) for our synthetic strategy because 1) its clawlike donor atoms and bent coordination geometry offer the possibility of incorporating more metal atoms into high-nuclearity clusters, and 2) ligands containing a large number of N atoms could partially reduce Mo VI to Mo V , [12] whereby the surface charge density of the polyanion is increased and the surface oxygen atoms are activated to facilitate formation of high-dimensional covalent networks. Herein we report the synthesis, structure, and luminescent and electrochemical properties of an unprecedented (4,12)-connected 3D network, namely, (NH 4

Keggin POMs Modified by Bonding to Multitrack Cu(bipy) Chains through Linearly Arrayed Terminal and Bridging Oxygen Atoms of the M3O13 Triad

“…[3] Recently, a number of Keggin POMs covalently modified by transition-metal complexes have been reported, such as the mixed-valent compounds [{Cu 4 (terpy) 4 4 )}]· 5H 2 O described by Zubieta et al, [4] [PW 12 O 40 ·Ni(2,2-bipy) 2 -(H 2 O)] 3-by Xu et al, [5] and (NH 4 [6] the controlled assembly from lacunary Keggin POMs has also been reported by Pope et al [7] and Gutiérrez-Zorrilla et al [8] All these compounds featured sufficient charge density on the Keggin anion surface atoms to coordinate the transition-metal complexes. It is believed that surface activation is achieved by reducing the metal centres or by replacing metal centre(s) with a high oxidation state by other lower-valence metal(s).…”

Synthesis, Structural Investigation and Characterization of an α-Keggin-based Organic-Inorganic Hybrid, [Cu(BIIM)2]{[Cu(BIIM)2(H2O)][Cu(BIIM)2BW12O40]·3H2O}2 (BIIM = 2,2´-Biimidazole)

“…The Cu(1)-centered square pyramid is defined by four N atoms from two BIIM ligands in the basal plane and an apical oxygen atom bridging to a WO 6 octahedron with a Cu(1)−O distance of 2.349(7)Å and Cu(1)−N bond lengths in the range of 1.995(9) -2.020(9)Å. The coordination environment of the Cu(2) site is similar to that of Cu(1), but the apical oxygen position is occupied by a water molecule with a Cu(2)−O(1W) bond length of 2.272 (8) and Cu(2)−N distances varying from 2.008 (9) …”

Nanoscale Fluorescence Emitters

“…The assembled nanocomposites may contain nanoparticles or clusters of different dimensionalities (Srivastava and Kotov 2009 ). Precise 3D self-assembly is possible with nanocomposites (Wang et al 2006b ), as it will be seen in Chap. 6 .…”