A cationic copper-iodine cluster-based metal-organic framework (MOF) with (4, 8)-connected fluorite topology

Recent Advances of Precise Cu Nanoclusters in Microporous Materials

This minireview highlights some recent advances in the rational design of precise Cu nanoclusters supported on microporous materials, including zeolites and metal-organic frameworks. The development of comprehensive characterisation techniques enables scientists to elucidate the structure-activity relationship of these catalysts, which aids the subsequent engineering of more superior catalytic systems at an atomistic perspective.

Hydrosoluble Cu(i)-DAPTA complexes: synthesis, characterization, luminescence thermochromism and catalytic activity for microwave-assisted three-component azide-alkyne cycloaddition click reaction

New hydrosoluble and air-stable Cu(i) halide compounds, viz. [CuX(DAPTA)3] (1) and (2), and [Cu(μ-X)(DAPTA)2]2 (3) and (4) (X = Br or I, in this order), have been prepared by reacting Cu(i) halide (i.e., bromide or iodide) with 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) under mild conditions. They represent the first examples of Cu(i) halide complexes bearing the DAPTA ligand, which have been fully characterized by elemental analysis, IR, 1H, 13C{1H} and 31P{1H} NMR spectroscopies, ESI-MS+ and, for 4, also by single-crystal X-ray diffraction (SCXRD) analyses. Complexes 1-4 are efficient catalysts for the one-pot microwave assisted three-component (terminal alkyne, organic halide and NaN3) Huisgen cycloaddition reaction in aqueous media to afford the corresponding disubstituted triazoles. The catalysis proceeds with a broad alkyne substrate scope and according to "click rules". Photophysical studies of compound 4 showed an unusual reversible thermochromic behaviour exhibiting a blue emission at 298 K due to the halide-to-ligand charge transfer (3XLCT) and a red emission at 77 K because of the {Cu2I2} unit.

Thermochromic and mechanochromic luminescence umpolung in isostructural metal-organic frameworks based on Cu6I6 clusters

Two isostructural metal-organic framework (MOF) materials, namely, {[MeSi((3)Py)3]6(Cu6I6)}n (1) and {[ MeSi((3)Qy)3]6(Cu6I6)}n (2), featuring Cu6I6 clusters were synthesized from tridentate arylsilane ligands of the type MeSi((3)Py)3 ((3)Py = 3-pyridyl) and MeSi((3)Qy)3 ((3)Qy = 3-quinolyl), respectively. While the MOF 1 displays the usual thermochromism associated with traditional Cu4I4Py4 clusters, the MOF 2 shows (3)XLCT/(3)MLCT emission due to the Cu6I6 cluster core at both 298 and 77 K, albeit with some marginal variations in its emission wavelengths. Interestingly, an unusual reversal in the mechanochromic luminescent behavior was observed for these isostructural MOFs at 298 K wherein a pronounced blue-shifted high energy emission for 1 (from orange to yellowish-orange) and a red-shifted low-energy emission for 2 (from green to orange) were obtained upon grinding these samples. This is primarily due to the variations in their cuprophilic interactions as 1 displays shorter Cu···Cu distances (2.745(1) Å) in comparison with those present in 2 (3.148(0) Å). As a result, the ground sample of 2 exhibits a prominent red shift in luminescence owing to the reduction of its Cu···Cu distances to an unknown value closer to the sum of van der Waals radii between two Cu(I) atoms (2.80 Å). However, the blue-shifted emission in 1 is presumably attributed to the rise in its lowest unoccupied molecular orbital energy levels caused by changes in the secondary packing forces. Furthermore, the absorption and emission characteristics of 1 and 2 were substantiated by time-dependent density functional theory calculations on their discrete-model compounds. In addition, the syntheses, reactivity studies, and photophysical properties of two one-dimensional MOFs, namely, {[MeSi((3)Qy)3]2(Cu2I2)}n (3) and {[MeSi((3)Qy)3](CuI)}n (4), having dimeric Cu2I2 and monomeric CuI moieties, respectively, were examined.

Copper-organic frameworks assembled from in situ generated 5-(4-pyridyl)tetrazole building blocks: synthesis, structural features, topological analysis and catalytic oxidation of alcohols

Two new metal-organic compounds {[Cu3(μ3-4-ptz)4(μ2-N3)2(DMF)2](DMF)2}n (1) and {[Cu(4-ptz)2(H2O)2]}n (2) {4-ptz = 5-(4-pyridyl)tetrazolate} with 3D and 2D coordination networks, respectively, have been synthesized while studying the effect of reaction conditions on the coordination modes of 4-pytz by employing the [2 + 3] cycloaddition as a tool for generating in situ the 5-substituted tetrazole ligands from 4-pyridinecarbonitrile and NaN3 in the presence of a copper(ii) salt. The obtained compounds have been structurally characterized and the topological analysis of 1 discloses a topologically unique trinodal 3,5,6-connected 3D network which, upon further simplification, results in a uninodal 8-connected underlying net with the bcu (body centred cubic) topology driven by the [Cu3(μ2-N3)2] cluster nodes and μ3-4-ptz linkers. In contrast, the 2D metal-organic network in 2 has been classified as a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology assembled from the Cu nodes and μ2-4-ptz linkers. The catalytic investigations disclosed that 1 and 2 act as active catalyst precursors towards the microwave-assisted homogeneous oxidation of secondary alcohols (1-phenylethanol, cyclohexanol, 2-hexanol, 3-hexanol, 2-octanol and 3-octanol) with tert-butylhydroperoxide, leading to the yields of the corresponding ketones up to 86% (TOF = 430 h(-1)) and 58% (TOF = 290 h(-1)) in the oxidation of 1-phenylethanol and cyclohexanol, respectively, after 1 h under low power (10 W) microwave irradiation, and in the absence of any added solvent or additive.

A cationic copper(i) iodide cluster MOF exhibiting unusual ligand assisted thermochromism

A cationic CuI cluster MOF 1, {Cu₆I₅[(NHAQ)₃PS]₂(OH)·3DMF·2.5MeOH}_n (AQ = 3-quinolinyl), was shown to exhibit an unusual thermochromic luminescent behaviour emitting a blue fluorescence at 298 K and a pale-orange phosphorescence at 77 K.