Halide Clusters Research Articles

A Luminescent Three-Dimensional Coordination Polymer Based on Cu(I) Halide Clusters Showing Dia Topology with 8-Fold Interpenetration

One interesting copper(I) halide-based coordination polymer with a formula of [Cu4(Br)4(bib)2]n (1) (bib = 1,4-bis(imidazol-2-methyl)butane) has been prepared by solvothermal method, and characterized by X-ray single crystal diffraction, elemental analyses, IR and TGA. Structure analyses reveal that the compound is constructed of copper(I) halide clusters and flexible bib ligands, which features a 8-fold interpenetrated 3D framework with 4-connected extended dia topology. Furthermore, the compound exhibits high thermal stability and intense fluorescent emission, and can be explored for potential red luminescent materials.

PH-Dependent Self-Assembly of Ladder-Like Lanthanide Chains with Copper(I) Halide Clusters.

Through adjustment of the pH value of the reaction system, two series of 3 D lanthanide(III)-copper(I) coordination polymers, namely [Ln2 (na)7 Cu6 Br5 (H2 O)2 ] [Ln=La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8)] and [La2 (na)7 Cu3 Br2 (H2 O)2 ]⋅H2 O (9) (na- =nicotinate), are synthesized hydrothermally and characterized fully. It is worth nothing that these two series of heterometallic compounds are constructed from similar ladder-like Ln-organic chains, but different copper(I) halide clusters. The luminescence properties of the compounds with Nd (4), Eu (6), and Tb (8) are also investigated.

ChemInform Abstract: Surprising Intrazeolitic Chemistry of Silver

AbstractReview: 44 refs.

Surprising Intrazeolitic Chemistry of Silver

New small molecules and cations have been synthesized within silver-containing zeolites, and their structures were determined using single-crystal crystallography. Some of them are the hydronitrogens N3H5 and cyclo-N3H3, octahedral Ag6, and the silver halide clusters Ag4Cl4, Ag4Br4, and Ag4I4. The silver halide clusters within their zeolites are ordered three-dimensional arrangements of identical quantum dots. The (C3O3H3)22+ cation is a reduced dimer of C3O3H33+ (tripyrylium); tripyrylium is planar and isoelectronic with benzene. The two rings bond together facially via their π* orbitals in an eclipsed manner with a very short interplanar distance, 2.43 Å. When a hydrated silver-exchanged zeolite is heated (to dehydrate it), Ag+ ions react with framework oxygen atoms to give silver atoms and O2(g); this leads to crystal damage and the complete loss of crystalline diffraction. This damage, however, can be repaired and the diffraction fully restored by heating in O2(g). To avoid crystal damage altogether, silver-exchanged zeolites can be dehydrated at elevated temperatures in flowing O2(g).

Copper(i) halide clusters based upon ferrocenylchalcogenoether ligands: donors, halides and semi-rigidity effects on the geometry and catalytic activity.

Six copper(i) halide clusters based upon ferrocenyltelluroethers or ferrocenylselenoethers, 1-6, have been synthesized and structurally characterized by an X-ray crystallographic study. These structures include a discrete step-cubane Cu4I4 cluster, a 1D chain with rhomboid Cu2X2 clusters, a 1D chain with cubane Cu4I4 clusters and a 2D network with Cu2I2 clusters. 1-3 are the first structurally characterized example of copper(i) clusters with telluroethers. Their different nuclearities and geometries can be attributed to the different donor atoms and chain flexibility in the ligands. The catalytic activities of six clusters were then investigated in the Ullmann C-N cross-coupling reaction and 2 displayed the best performance with a target product N-(4-phenyl)imidazole in 91.3% yield. From the viewpoint of structure, the specific steric acceptance around Cu(i) in 2 may allow imidazole and iodobenzene to stepwise coordinate with the copper center and give the target product effectively.

Synthesis, structures and luminescence properties of 3d–4f heterometallic–organic frameworks (HMOFs) constructed from different copper halide clusters

Four novel 3d–4f heterometallic–organic frameworks (HMOFs), namely [Gd2(Cu2I2)(C6H4NO2)6(C3H7NO)(H2O)]·(C3H7NO) (1), [Gd2(Cu4I4)(C6H4NO2)6(C3H7NO)2] (2), [Gd2(Cu6I6)(C12H8NO2)6(C2H6O)2(H2O)2] (3) and [Gd2(Cu8I8)(C12H8NO2)6(H2O)4]·5(C4H8O2) (4), have been solvothermally synthesized and characterized. The four compounds incorporate Cu2I2, Cu4I4, Cu6I6 and Cu8I8 clusters in three-dimensional frameworks, respectively, and the influence of Ln3+ ions, copper halide clusters and ligands on the construction of the structures has been analyzed. The four compounds display four different emission colours. Interestingly, compound 3 responds to external mechanical force. After grinding, the fluorescence has been obviously quenched. Compound 4 displays a reversible luminescence behavior, accompanying the removal and recovery of the guest molecules in the channel.

Halide coordinated homoleptic [Fe4S4X4](2-) and heteroleptic [Fe4S4X2Y2](2-) clusters (X, Y = Cl, Br, I)--alternative preparations, structural analogies and spectroscopic properties in solution and solid state.

New facile methods to prepare iron sulphur halide clusters [Fe4S4X4](2-) from [Fe(CO)5] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(ii) or simple ferrous halides with [Fe(CO)5] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4](2-) (X = Cl, Br) and heteroleptic clusters [Fe4S4X4-nYn](2-) (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA(+) (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4](2-) and [Fe4S4X2Y2](2-) (X, Y = Cl, Br, I) were all isostructural to (BTMA)2[Fe4S4I4] (monoclinic, Cc) as inferred from synchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4-nYn](2-) clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions.

Crystal Engineering with 2-Aminopurine and 2,6-Diaminopurine Derivatives: Dimers, Metallaquartets, and Halide-Bridged Clusters

Design, synthesis, and single crystal structure elucidation of modified purine ligands 2-(2-amino-9H-purin-9-yl) acetic acid (L1) and 2-(2,6-diamino-9H-purin-9-yl) acetic acid (L2) and their interaction with certain d10 transition metal ions is described. Copper complex 1 (C28H34Cu2N22O19) afforded a two-dimensional polymeric structure composed of metallaquartets, while corresponding silver complex 2 (C14H20AgN10O8) was formed as a discrete dimer. Complexes 3 (C14H24CdN10O10) and 5 (C14H22CdN12O8), cadmium complexes of L1 and L2, respectively, afforded different coordinating modes, where 3 resulted in a two-dimensional (2D) polymeric structure consisting of metallaquartets and 5 as a discrete dimeric structure, with an octahedral coordination geometry. Complex 4 (C14H13Cl13Hg6N10O8) afforded a unique hexanuclear, 2D polymeric structure, supported by mercury-chloride bridges, presenting as interconnected dimeric, trimeric, and hexameric mercury halide (μ2double, μ3triple, and μ6six) clusters. The potential of halide ions as bridges is interesting. We have also studied the fluorescence properties of ligand L1 and L2 along with complexes 1–5.

Three silver (I) supramolecular compounds constructed from pyridinium or methylimidazolium polycations: Synthesis, crystal structure and properties

Three metal halide cluster supramolecular polymers, {(TBP)[Ag3Br6]}n (1), {(TBI)[Ag3Br6]}n (2) and {(TBP)[Ag3I6]}n(3) (TBP =1, 3, 5-tris(N-pyridinium methyl)benzene, TBI =1, 3, 5-tris(methylimidazole methyl)benzene), have been synthesized and characterized by thermoanalysis and spectroscopic methods, as well as single-crystal X-ray diffraction. Complexes 1, 2 and 3 all feature a one-dimensional chain structure, which is further extended by electrostatic attraction. The TGA, UV-Vis diffuse reflectance spectra in the solid state and optical band gap properties of the three complexes were also investigated.

Thermal Activation of Solid-State Molybdenum Halide Clusters with an Octahedral Cluster Framework and Their Application to Catalytic Synthesis of 3-Methylpyridine from Piperidine and Methanol

Abstract Solid-state molybdenum halide clusters with an octahedral metal framework MoX2 (or [Mo6X8]X2X4/2) (X = Cl, Br, I) are applied to catalysis. When these clusters are thermally activated in a hydrogen stream above 300 °C, they exhibit catalytic activity for the dehydrogenative C-methylation of piperidine with methanol, to yield 3-methylpyridine. At 400 °C, the selectivity is as high as 74%. This catalytic behavior is different from that of the molecular clusters [(M6Cl12)Cl2(H2O)4]·4H2O (M = Nb, Ta) and (H3O)2[(M6Cl8)Cl6]·6H2O (M = Mo, W), which exhibit Brønsted acidity after thermal activation; piperidine is N-methylated to yield N-methylpiperidine selectively. Elemental analysis and thermogravimetric analysis demonstrate that the solid-state clusters partially eliminate halogen ligands during the activation. Infrared analysis of adsorbed pyridine on the activated clusters shows the presence of a Lewis acid site. This coordinatively unsaturated site of the molybdenum is catalytically active for dehydrogenative C-methylation. The formation of an η3-1-azaallyl species on the molybdenum facilitates the methylation at the 3-position of piperidine, followed by dehydrogenation to yield 3-methylpyridine.

Coordinative versatility of 3,5-bis(4-pyridyl)-1,2,4-triazole in the construction of monomeric copper(II) and polymeric copper(I) complexes

Three complexes, namely [Cu(dpt)2(H2O)4]·2H2O (1), [Cu3I2(dpt)] n (2) and [Cu6Br3(dpt)3] n (3), have been obtained from the reactions of different copper salts with 1H-3,5-bis(4-pyridyl)-1,2,4-triazole (Hdpt). Complex 1 is mononuclear such that the CuII atom exhibits an octahedral coordination geometry involving monodentate dpt ligands, being synthesized from CuII nitrate and Hdpt at ambient temperature, while the cuprous halide cluster-based coordination polymers 2 and 3 were prepared by solvothermal reactions of CuI or CuBr with Hdpt. Complex 2 consists of [Cu3I2] n chains, which are further connected by the μ 4-dpt bridges to form a 4,6-connected three-dimensional coordination polymer. Complex 3 is a 3,3,9-connected net based on [Cu6Br3] building blocks, linked by μ 3-dpt bridges. The photoluminescence properties of complex 2 in the solid state at ambient temperature have been investigated. Syntheses and structures of three complexes [Cu(dpt)2(H2O)4]·2H2O (1), [Cu3I2(dpt)] n (2) and [Cu6Br3(dpt)3] n (3) (Hdpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole) are described, in which the effect of the rich connectivity of the cuprous halide clusters, supported by the changeable coordination modes of dpt ligand, is revealed.

Subtle Modulation of Cu4X4L2 Phosphine Cluster Cores Leads to Changes in Luminescence.

A series of Cu4X4(PPh2py)2 compounds (X = Cl (1), Br (2), I (3), PPh2py = 2-(diphenylphosphino)pyridine) were prepared and characterized using X-ray crystallography, NMR, UV-vis, and luminescence spectroscopy. The copper chloride and bromide clusters have Cu4X4 octahedral cores while the copper iodide clusters contain an unprecedented butterfly shaped core. Crystallization of the copper bromide and iodide clusters from the appropriate solvent produced the solvates 2·2CH2Cl2, 2·2CHCl3, and 3·0.5CH2Cl2 where the presence of the lattice solvate influences the overall structural properties. Using TD-DFT calculations, the emission was assigned to a mixed metal- and halide-to-ligand charge transfer, (M + X)LCT. Subtle differences in the copper core geometry and μ-halide bonding perturb the emissions of these copper(I) halide clusters.

Synthesis of Common-sized Heterocyclic Compounds by Intramolecular Cyclization over Halide Cluster Catalysts

Abstract Five- to seven-membered common-sized heterocyclic compounds containing an oxygen, sulfur, or nitrogen were synthesized by the intramolecular condensation of α,ω-hydroxy, mercapto, or amino alkanes, respectively, over halide cluster complexes as a thermally stable molecular solid weak acid catalyst in the gas phase at temperatures ≥150 °C. From ω-mercapto and ω-amino alcohols, cyclic sulfides and amines were obtained, respectively. These unimolecular reactions are thermodynamically and kinetically favored.

Thermodynamics of small alkali metal halide cluster ions: comparison of classical molecular simulations with experiment and quantum chemistry.

We evaluate the ability of selected classical molecular models to describe the thermodynamic and structural aspects of gas-phase hydration of alkali metal halide ions and the formation of small water clusters. To understand the effect of many-body interactions (polarization) and charge penetration effects on the accuracy of a force field, we perform Monte Carlo simulations with three rigid water models using different functional forms to account for these effects: (i) point charge nonpolarizable SPC/E, (ii) Drude point charge polarizable SWM4-DP, and (iii) Drude Gaussian charge polarizable BK3. Model predictions are compared with experimental Gibbs free energies and enthalpies of ion hydration, and with microscopic structural properties obtained from quantum DFT calculations. We find that all three models provide comparable predictions for pure water clusters and cation hydration but differ significantly in their description of anion hydration. None of the investigated classical force fields can consistently and quantitatively reproduce the experimental gas-phase hydration thermodynamics. The outcome of this study highlights the relation between the functional form that describes the effective intermolecular interactions and the accuracy of the resulting ion hydration properties.

ChemInform Abstract: Characterization of Catalytically Active Octahedral Metal Halide Cluster Complexes

AbstractReview: 43 refs.

Surface site coordination dependent responses resolved in free clusters: applications for neutral sub-nanometer cluster studies.

In this paper we demonstrate how surface site specific experimental information can be obtained from free low nanometer scale clusters using photoelectron spectroscopy utilising synchrotron radiation. In addition, we show how it can be used to gain insight into the geometry and surface structure of the clusters. The present experiments were conducted on alkali metal halides, RbCl and CsCl, which were chosen as advantageous test cases due to their simple electronic and geometric structures. These heavy alkali metal salts provide additional clarity since the surface and bulk responses can be separated, which is not the case for clusters of lighter alkali metal salts. Computational chemical shift calculations and simple alkali halide cluster size modelling were used to interpret the experimental results.

Reversible photoluminescence switching behavior and luminescence thermochromism of copper(I) halide cluster coordination polymers

The coordinated CH3CN play the role of an unusual reversible photoluminescence switch to perfectly modulate the luminescence in a copper(i) halide cluster coordination polymer.

Electron counting rules and electronic structure in tetrameric transition-metal (T)-centered rare-Earth (R) cluster complex halides (X).

Electron partition schemes are a beneficial means to systematize bonding networks and to identify structure-bonding relationships in polar intermetallics. One prolific class of polymetal networks with simple counterions is the broad family of transition-metal (T)-centered rare-earth metal (R) cluster halides (X), which can be isolated or condensed to oligomers and chains. While the electronic structures of R cluster monomers and chains encapsulating T atoms have been studied systematically, the band structures of oligomers, in particular, the most frequent Friauf-type {T(4)R(16)} tetramers, have been investigated to a lesser extent. Therefore, the band structures of prototypical compounds with {T(4)R(16)}-type tetramers, while maintaining different compositions, were analyzed employing density functional theory based methods. Furthermore, these theoretical examinations provide insight into the origin of the 15 electron rule, which is significant for this class of compounds and correlates with the closed-shell configurations for these structures. Additional research focused on the band structure of monoclinic {Ru(4)Gd(16)}Br(23), which is composed of rhomboid-shaped {Ru(4)Gd(16)} tetramers.

Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms

Comproportionation reactions of rare-earth metal trihalides (RX3) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ({T3R11}X15-type, P63/m), tetramers ({T4R16}X28{R4} (P-43m), {T4R16}X20 (P42/nnm), {T4R16}X24(RX3)4 (I41/a) and {T4R16}X23 (C2/m) types of structure) and pentamers ({Ru5La14}2Br39, Cc) of {TRr}n (n=2–5) clusters. These oligomers are further enveloped by inner (Xi) as well as outer (Xa) halido ligands, which possess diverse functionalities and interconnect like oligomers through i–i, i–a and/or a–i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of {TR6} octahedra via common edges are more frequent than trimers and pentamers, in which the {TRr} clusters share common faces.

Catalytic Reactions over Halide Cluster Complexes of Group 5–7 Metals

Halide clusters of Group 5–7 metals develop catalytic activity above 150–250 °C, and the activity is retained up to 350–450 °C by taking advantage of their thermal stability, low vapor pressure, and high melting point. Two types of active site function: the solid Brønsted acid site and a coordinatively unsaturated site that catalyzes like the platinum metals do. Various types of catalytic reactions including new reactions and concerted catalyses have been observed over the clusters: hydrogenation, dehydrogenation, hydrogenolysis, isomerization of alkene and alkyne, and alkylation of toluene, amine, phenol, and thiol. Ring-closure reactions to afford quinoline, benzofuran, indene, and heterocyclic common rings are also catalyzed. Beckmann rearrangement, S-acylation of thiol, and dehydrohalogenation are also catalyzed. Although the majority of the reactions proceed over conventional catalysts, closer inspection shows some conspicuous features, particularly in terms of selectivity. Halide cluster catalysts are characterized by some aspects: cluster counter anion is too large to abstract counter cation from the protonated reactants, cluster catalyst is not poisoned by halogen and sulfur atoms. Among others, cluster catalysts are stable at high temperatures up to 350–450 °C. At high temperatures, apparent activation energy decreases, and hence weak acid can be a catalyst without decomposing reactants.