Supramolecular Assembly Based on Octamolybdate and Triazole Derivative: Crystal Structure and Catalytic Application in Olefin Epoxidation

A novel polyoxometalate-based compound, [H(atrz)]₄[(atrz)₂(Mo₈O₂₆)]·2H₂O (1) (atrz = 3-amino-1,2,4-triazole), has been synthesized by traditional hydrothermal method, and characterized by means of elemental analysis, FT-IR spectroscopy, Powder X-ray diffraction and single-crystal X-ray. The compound 1 contains a 2D supramolecualr layer which is constructed from [(atrz)₂(γ-Mo₈O₂₆)]^4? units via intermolecular hydrogen-bonding interactions. Furthermore, the adjacent 2D layers are packed together through the aromatic π?π stacking interactions and exhibits a 3D supramolecular structure. The catalytic properties of 1 were investigated in olefin epoxidation with tert-butylhydroperoxide (t-BuOOH) as the oxidant. It was found that compound 1 could serve as active and stable heterogeneous catalyst for the epoxidation of cyclooctene and 1-octence. Besides, introducing copper ions into compound 1 could further improve the catalytic activity for olefin epoxidation.     

Synthesis, Crystal Structure and Thermal Analysis of (TAGH)2(TNR)

A new energetic compound (TAGH)₂(TNR) (TAG: triaminoguanidine, TNR: 2,4,6-trinitroresorcinol) was prepared by reacting triaminoguanidine with 2,4,6-trinitroresorcinol (styphnic acid) in aqueous solution under nitrogen atmosphere, and characterized by elemental analysis and Fourier transform infrared (FTIR) spectra. Its crystal structure was determined by single crystal X-ray diffraction analysis. The crystal belonged to a monoclinic, C 2/c space group. The unit cell parameters were as follows: a=2.2892(6) nm, b=1.2802(3) nm, c=1.3661(4) nm, β=111.174(5)°, V=3.7333(16) nm³, and Z=8. The compound consisted of two cations C(N₂H₃)₃⁺ and an anion (C₆HN₃O₈)²⁻. The C(N₂H₃)₃⁺ and (C₆HN₃O₈)²⁻ were bonded together by electrostatic attraction and hydrogen bonds, and this effect made the compound more stable. The thermal analysis of the compound was studied by using differential scanning calorimetry (DSC), thermogravimetry-derivative thermogravimetry (TG-DTG). Under nitrogen atmosphere with a heating rate of 10 K·min⁻¹, the thermal decomposition of the compound contained only one intense exothermic decomposition process in the range of 450.1-477.7 K in the DSC curve, and the decomposition products were nearly gaseous products.     

Synthesis and Characterization of a One-dimensional Coordination Polymer Generated from Unsymmetrical Bridging Organosulfur Ligand

A new one-dimensional（1D） coordination polymer [Zn（MMTA）2]n（MMTA=5-mercapto-l-methyl-tetrazole） was synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction. This compound crystallizes in the monoclinic space group C2/c, with cell parameters： a=1.4938（7） nm, b=1.3599（5） nm, c=1.2180（4） nm, fl=120.84（3）^＊, V=2.1243（2） nm^3, and Z=8. The deprotonated HMMTA molecule as a/a2-1igand links the zinc center, forming ID chains, which are luther linked by weak C--H...N hydrogen bonds, forming a three-dimensional supramolecular framework. The compound exhibits intense photoluminescence at room temperature. On the basis of the results of TG/DTA analyses, the structure is thermally stable up to -280 ℃.     

A multi-functional 3D polymolybdate-based copper(II) complex based on an asymmetric pyridyl-amide ligand: synthesis,structure and properties

A polymolybdate-based metal–organic compound {H₂[Cu₂(L)₂(Mo₈O₂₇)(H₂O)₄]} (1) [L = N-(pyridin-3-yl)isonicotinamide] has been synthesized under solvothermal (methanol–water mixed solvent) conditions and structurally characterized by single-crystal X-ray diffraction. Compound 1 exhibits a 3D metal–organic network containing unusual 1D [Mo₈O₂₇] _n ^6n? inorganic chains, with adjacent 1D chains connected by Cu(II) atoms and L ligands to form a 3D framework with a trinodal 4,4,6-connected {4².6³.8}₂{4⁴.6⁸.8³} topology. The electrocatalytic activities of compound 1 and its photocatalytic properties for the degradation of organic dyes have also been investigated.     

Crystal structure and fluorescent properties of a 2D cadmium coordination polymer

A new 2D cadmium(II) coordination polymer {[Cd(MBD)(L)]·(H₂O)₂} _n (1) (H₂MBD = 5-methoxycarbonyl-benzene-1,3-dicarboxylic acid, L = 1,3-bis(benzimidazol-l-yl)-2-propanol) is synthesized, in which the starting linker (benzene-1,3,5-tricarboxylic acid) undergoes selective monoesterification during the synthesis. In the structure of complex 1, each cadmium center is octahedrally coordinated by four O atoms from three carboxylate groups and two N of distinct L ligands. A detailed structural analysis reveales that compound 1 exhibits a unique 2D binodal (3,5)-connected (4².6⁷.8)(4².6) topology structure. Furthermore, the 2D layer is extended into a 3D network through π-π stacking interactions. The solid-state fluorescence properties of 1 are investigated at room temperature.     

Assembly of a New 3D Octamolybdate‐based Compound: Using the Flexible Bis(triazole) ligand with a –(CH2)6– Spacer

Through utilizing the flexible bis(triazole) ligand 1, 6‐bis(1, 2, 4‐triazol‐1‐yl)hexane (btx), a new octamolybdate‐based compound, [Cu₂(btx)₄(β‐Mo₈O₂₆)] · H₂O ( 1 ), was synthesized under hydrothermal conditions. It was characterized by single‐crystal X‐ray diffraction, elemental analyses, IR spectroscopy, thermogravimetric analysis, and cyclic voltammetry. In compound 1 , the [β‐Mo₈O₂₆]^4– anion acts as a bi‐connected inorganic linkage to connect the Cu‐btx moieties. The Cu1‐btx moiety linked by the [β‐Mo₈O₂₆]^4– anions exhibits a 2D layer, while the Cu2‐btx moiety also shows a similar 2D layer. Furthermore, these two 2D moieties construct a 3D framework through sharing the same N7‐containing btx ligands.     

Synthesis and characterization of two novel coordination polymers based on the rigid 1H-1,2,3-triazole-4,5-dicarboxylic acid ligand

Two novel three-dimensional (3-D) coordination polymers, [Pb(HTDA)] _n (1) and [Co₅(TDA)₂(H₂TDA)₂(H₂O)₈] _n (2) [H₃TDA = 1H-1,2,3-triazole-4,5-dicarboxylic acid], have been prepared by hydrothermal reactions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction. Compound 1 is constructed from rod-shaped secondary building units (SBUs) and exhibits a 3-D network with (4¹⁰·6⁵)(4¹⁰·6³·8²) topology. Compound 2 is built up from ligands bridging three different cobalt ions and exhibits a 3-D network with (4·8²)₃(4·8²·10³) topology. In addition, the thermal stabilities of the two compounds, the photoluminescence properties of compound 1 and the magnetic properties of compound 2 have been studied.     

Assembly of an interpenetrating three-dimensional mixed-valence Cu/Cu coordination polymer

A novel cyano-bridged three-dimensional mixed-valence Cu(II)/Cu(I) compound [Cu₂(oxpn)][Cu(CN)₂]₂ (oxpn²⁻ = dianion of N,N^′-bis(3-aminopropyl)oxamide) has been synthesized and structurally characterized. Single crystals of 1 formed by diffusion of Cu₂(oxpn)Cl₂ and K₃[Cr(CN)₅(NO)] in H₂O for two months. The structure of the title compound consists of threefold interpenetrating 3D frameworks. In each 3D network, oxamidato-bridged dimeric [Cu₂(oxpn)]²⁺ units connect 1D polymeric [Cu(CN)₂]⁻ anions giving rise to a 3D structure. Room temperature magnetic measurement shows the presence of strong magnetic coupling between the Cu(II) ions. Electronic paramagnetic resonance spectrum measurements show the transitions due to the excited triplet state.     

Heterometallic Mixed‐Valence Copper(I,II) Cyanides that were Tuned by Using the Chelate Effect: Discovery of Famous Cairo Pentagonal Tiling and Unprecedented (3,4)‐Connected {83}2{86} Topological 3D Net

By using environmentally friendly [Ni(CN)₄]^2? as a cyanide source, three new heterometallic cyano‐bridged mixed‐valence Cu^I/Cu^II coordination polymers with three different electronic configurations (d⁸–d¹⁰), that is, [Cu₂Ni(CN)₅(H₂O)₃] ( 1 ), [Cu₂Ni(CN)₅(pn)H₂O] ( 2 ), and [Cu₃Ni(CN)₆(pn)₂] ( 3 , pn=1,2‐propane diamine) have been synthesized by gradually increasing the amount of pn. Compound 1 , which was hydrothermally synthesized in the absence of pn ligand, exhibits the famous 2D Cairo pentagonal tiling, in which the Cu^I, Cu^II, and Ni^II atoms act as trigonal, T‐shaped, and square‐planar nodes, respectively. Notably, there are three water molecules located at the meridianal positions of the octahedrally coordinated Cu^II atom in compound 1 . A similar reaction, except for the addition of a small amount of pn, generated a similar Cairo pentagonal tiling layer in which two of the water molecules that were located at the meridianal positions of the octahedrally coordinated Cu^II atom were replaced by a chelating pn group. Another similar hydrothermal reaction, with the addition of a larger amount of pn, yielded compound 3 , which showed a related two‐fold‐interpenetrated (3,4)‐connected 3D framework with an unprecedented {8³}₂{8⁶} topology in which the Cu^II atom was chelated by two pn groups. These structural changes between compounds 1 , 2 , 3 can be explained by the chelating effect of the pn group. The replacement of two meridianally coordinated water molecules on the octahedral Cu^II atom in compound 1 by a pn group gives compound 2 , which shows similar Cairo tiling, and a further increase in the amount of pn results in the formation of the [Cu(NC)₂(pn)₂] unit and the two‐fold‐interpenetrated 3D framework of compound 3 . The mixed‐valence properties of compounds 1 , 2 , and 3 were confirmed by variable‐temperature magnetic‐susceptibility measurements.     

Syntheses, characterizations and crystal structures of two new lead(II) amino and carboxylate-sulfonates with a layered and a pillared layered structure

Reactions of lead(II) acetate with m-aminobenzenesulfonic acid (HL¹) and 5-sulfoisophthalic acid (H₃L²) afforded two new lead(II) sulfonates, Pb(L¹)₂1 and Pb₂(L²)(μ₃-OH)(H₂O) 2. In compound 1, the lead(II) ion is eight-coordinated by two sulfonate groups bidentately, two sulfonate groups unidentately and two amino groups from six ligands. Each L¹ ligand is tetradentate and bridges with three Pb(II) ions. The interconnection of the Pb(II) ions via bridging sulfonate ligands resulted in 〈100〉 and 〈200〉 layers. In compound 2, one Pb(II) ion is six-coordinated by a carboxylate group bidentately, by two carboxylate groups unidentately, by a sulfonate oxygen atom and by an OH anion, whereas the other one is six-coordinated by a bidentate chelating carboxylate group, two μ₃-OH anions, a sulfonate oxygen atom and an aqua ligand. The interconnection of irregular PbO₆ polyhedra via carboxylate-sulfonate ligands resulted in the formation of a pillared layered structure with the 2D layer being formed; the lead(II) ions, hydroxyl groups, carboxylate and sulfonate groups and the benzene ring as the pillar agent.     

Luminescent and photocatalytic properties of a 6-connected msw-type 3D CdII metal–organic framework

Hydrothermal reactions of H₆bhc and Cd(NO₃)₂·4H₂O produced a new Cd^II compound [Cd₃(bhc)(H₂O)₈]_n (H₆bhc = benzene-1,2,3,4,5,6-hexacarboxylic acid). Single crystal X-ray diffraction analysis revealed that this compound features a 3D framework with bhc^6- ligands in a μ₆-bridging mode. Its luminescent and photocatalytic properties were explored.     

A re-investigation of the crystal structure and luminescence of BaCa2MgSi2O8:Eu

Barium calcium magnesium silicate (BaCa₂MgSi₂O₈), a compound whose space group was obtained via X-ray diffraction data, was re-investigated using neutron diffraction techniques. A combined powder X-ray and neutron Rietveld method revealed that BaCa₂MgSi₂O₈ crystallizes in the trigonal space group P3? (Z=1, a=5.42708(5) Å, c=6.79455(7) Å, V=173.310(4) Å³; R_p/R_wp=5.52%/7.63%), instead of the previously believed space group P3?m1. The difference in the two structures arises from the displacement of the O2 atom. Blue emission from Ba_0.98Eu_0.02Ca₂MgSi₂O₈ under 325-nm excitation is ascribed to the 4f⁶5d¹→4f⁷ transitions of Eu²⁺ ions at Ba sites and Ca sites. Site assignment of Eu²⁺ ions in the titled compound was performed by analysis of emission spectra at temperatures in the range of 4.2-300 K.     

2D-layered structure of coordination polymer,zinc trifluoroacetate-1,3-bis(4-pyridyl)propane

Compound [Zn(CF₃CO₂)₂(Bpp)₂], where Bpp is 1,3-bis(4-pyridyl)propane, was synthesized and its structure and luminescent properties were determined. Crystals are monoclinic, space group C2/c, a = 21.261(1) Å, b = 17.642(1) Å, c = 18.632(1) Å, β = 115.85(1)°, V = 6289.3(6) ų, ρ_calcd = 1.453 g/cm³, Z = 8. The structure comprises 2D neutral layers of conjugated multiunit rings composed of four Zn²⁺ ions united by four bridging Bpp ligands. Each of two crystallographically nonequivalent Zn atoms is coordinated at the octahedra apices to four nitrogen atoms of two Bpp ligands and two O(CF₃CO₂) atoms. Trifluoroacetate anions are coordinated to Zn²⁺ ions in monodentate manner. The compound exhibits photoluminescence in solid state.     

Synthesis, structure and magnetic properties of cobalt(II) and copper(II) coordination polymers assembled by phthalate and 4-methylimidazole

New coordination polymers [M(Pht)(4-MeIm)₂(H₂O)]_n (M=Co (1), Cu (2); Pht²⁻=dianion of o-phthalic acid; 4-MeIm=4-methylimidazole) have been synthesized and characterized by IR spectroscopy, X-ray crystallography, thermogravimetric analysis and magnetic measurements. The crystal structures of 1 and 2 are isostructural and consist of [M(4-MeIm)₂(H₂O)] building units linked in infinite 1D helical chains by 1,6-bridging phthalate ions which also act as chelating ligands through two O atoms from one carboxylate group in the case of 1. In complex 1, each Co(II) atom adopts a distorted octahedral N₂O₄ geometry being coordinated by two N atoms from two 4-MeIm, three O atoms of two phthalate residues and one O atom of a water molecule, whereas the square-pyramidal N₂O₃ coordination of the Cu(II) atom in 2 includes two N atoms of N-containing ligands, two O atoms of two carboxylate groups from different Pht, and a water molecule. An additional strong O-H?O hydrogen bond between a carboxylate group of the phthalate ligand and a coordinated water molecule join the 1D helical chains to form a 2D network in both compounds. The thermal dependences of the magnetic susceptibilities of the polymeric helical Co(II) chain compound 1 were simulated within the temperature range 20-300 K as a single ion case, whereas for the Cu(II) compound 2, the simulations between 25 and 300 K, were made for a linear chain using the Bonner-Fisher approximation. Modelling the experimental data of compound 1 with MAGPACK resulted in: g=2.6, |D|=62 cm⁻¹. Calculations using the Bonner-Fisher approximation gave the following result for compound 2: g=2.18, J=-0.4 cm⁻¹.     

A New 3D Manganese(II) Coordination Polymer with 4,4‐Dicarboxy‐2,2′‐bipyridine and 1,10‐Phenanthroline: Synthesis,Structural, and Magnetic Properties

A new 3D Mn^II metal‐organic framework compound {Mn(phen)(dcbp)}_n (H₂dcbp = 4,4‐dicarboxy‐2,2′‐bipyridine, phen = 1,10‐phenanthroline) was isolated under hydrothermal conditions and structurally characterized. In the compound, the dcbp ligand is deprotonated to give a neutral species (metal:ligand with 1:1 stoichiometry). Along the c axis, the neighboring Mn^II ions are linked by two carboxylate bridges in µ₂‐coordinating mode to generate a 1D zigzag chain, and these chains are interlinked by dicarboxylate groups of long dcbp ligands to generate a 3D (4,4)‐connected structure with the (4².8⁴) net topology. IR and UV/Vis spectroscopy and variable temperature magnetic susceptibility measurements were made, which indicated weak antiferromagnetic interactions between the Mn^II ions of the compound.     

Hydrothermal synthesis, structure and quantum chemistry of transition metal complex supported by metal-oxo cluster [(Ni(phen)2 2 (ξ-Mo8O26)]

A nickel-1,10-phenanthroline complex supported on an octamolybdate, [(Ni(phen)_{2 2}(ξ-Mo₈O₂₆)], has been hydrothermally synthesized with MoO₃, H₂MoO₄, Ni(OAc)₂ 6H₃O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P2₁/n space group,a = 1.2952(2),b = 1.6659(10),c = 1.3956(12) nm, β =106.273(8)°,V = 2.8906(5) nm³,Z = 2. 5604 observable reflections (I >2σ(I)) were used for structure resolution and refinements to converge to finalR ₁ = 0.0414,wR ₂ = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure type (named as ξ-isomer). The feature of ξ-[Mo₈O₂₆]^4- is that it is composed of Mo₆O₆ ring and two MoO₆ octahedral located at cap positions on opposite faces. The Mo₆O₆ ring contains two octahedral and four trigonal-bipyramidal Mo^VI atoms. Each ξ-[Mo₈O₂₆]^4- unit is bonded with two [Ni(phen)₂]²⁺ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo₆O₆ ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method.     

A Porous Cadmium(II) Framework: Synthesis,Crystal Structure,Gas Adsorption,and Fluorescence Sensing Properties

The Cd^II compound, namely [Cd(Tppa)(SO₄)(H₂O)]_n ( 1 ) [Tppa = tris(4‐(pyridyl)phenyl) amine], was synthesized by the reaction of CdSO₄ · 8H₂O and Tppa under solvothermal conditions. Single crystal X‐ray diffraction analysis revealed that compound 1 features a 3D porous framework based on 1D inorganic –[Cd–SO₄–Cd]_n– chains. Topological analysis reveals that compound 1 represents a trinodal (3,4,6)‐connected topological network with the point symbol of {6.7²}₂{6⁴.7.10}{6⁴.7⁵.8⁴.10²}. Gas adsorption properties investigations indicate that compound 1 exhibits moderate adsorption capacities for light hydrocarbons at room temperature. Luminescencence property studies revealed that this Cd^II compound exhibits high fluorescence sensitivity for sensing of CS₂ molecule.     

Syntheses, crystal structures, and characterization of As(III) and As(V) thioarsenates, [Mn2(phen)(As2S5)]n and [Mn3(phen)3(AsS4)2]n·nH2O

The hydrothermal reactions of As, Mn, S, phen (phen=1,10-phenanthroline), and en (en=ethylenediamine) yield two manganese As(III) and As(V) thioarsenates, [Mn₂(phen)(As^III₂S₅)]_n (1) and [Mn₃(phen)₃(As^VS₄)₂]_n·nH₂O (2), respectively. Single-crystal X-ray diffraction analyses reveal that compound 1 is a two-dimensional (2D) layer of (6,3) topology. The 18-membered rings within the 2D porous layers are formed by corner-, edge-, and face-sharing cubane-like [Mn₂As₂S₄] units along the [100] direction. Whereas compound 2 is a one-dimensional (1D) chain structure. They are both characterized by IR, elemental analysis, EDS, and X-ray powder diffraction. The thermogravimetric analysis of 1 and 2 are discussed. Both the compounds are semiconductors with the band gap of E_g (compound 1)=2.01 eV (617 nm) and E_g (compound 2)=1.97 eV (629 nm), respectively. In addition, the variable-temperature magnetic susceptibility data suggest weak antiferromagnetic interactions between the Mn²⁺ ions in these two compounds.     

A twofold interwoven two‐dimensional→two‐dimensional (2‐D→2‐D) cluster–organic network based on the [Cu2I2] cluster and the 4,4′‐(diazenediyl)dipyridine ligand: poly[[μ2‐4,4′‐(diazenediyl)dipyridine]‐μ2‐iodido‐copper(I)]

In the polymeric title compound, [CuI(C₁₀H₈N₄)]_n, the Cu^I atom is in a four‐coordinated tetrahedral geometry, formed by two I atoms and two pyridine N atoms from two different 4,4′‐(diazenediyl)dipyridine (4,4′‐azpy) ligands. Two μ₂‐I atoms link two Cu^I atoms to form a planar rhomboid [Cu₂I₂] cluster located on an inversion centre, where the distance between two Cu^I atoms is 2.7781 (15) Å and the Cu—I bond lengths are 2.6290 (13) and 2.7495 (15) Å. The bridging 4,4′‐azpy ligands connect the [Cu₂I₂] clusters into a two‐dimensional (2‐D) double‐layered grid‐like network [parallel to the (10) plane], with a (4,4)‐connected topology. Two 2‐D grid‐like networks interweave each other by long 4,4′‐azpy bridging ligands to form a dense 2‐D double‐layered network. To the best of our knowledge, this interwoven 2‐D→2‐D network is observed for the first time in [Cu₂I₂]–organic compounds.     

Synthesis,crystal structure,vibrational, optical properties,thermal analysis and theoretical study of a new Sn(IV) complex (C5H14N2)2[SnCl6]2·5H2O

In this study, a new organic-inorganic hybrid metal compound (C₅H₁₄N₂)₂[SnCl₆]₂·5H₂O was crystallized at room temperature in the orthorhombic system (space group P2₁ 2₁ 2₁) where the structure is determined by single crystal X-ray diffraction analysis. The examination of the structure shows the cohesion and stability of the atomic arrangement result from the establishment of N—H⋯Cl, O(W)—H(W)⋯Cl, N—H⋯O(W) and O(W)—H(W)⋯O(W) hydrogen bonds between 1-methylpiperazine-1,4-diium (C₅H₁₄N₂)²⁺cations, isolated (SnCl₆)^2– anions and water molecules to form organic and inorganic layers parallel to the (a, c) plane and alternate along the b-axis. Hirshfeld surface analysis was used to investigate intermolecular interactions, as well 2D fingerprint plots were conducted to reveal the contribution of these interactions in the crystal structure quantitatively. The solid phase FTIR and FT-Raman spectra of this compound have been recorded in the regions 400–4000 and 100–500 cm⁻¹, respectively. The vibrational frequencies were also predicted from the calculated intensities by DFT method and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. Besides, the optical proprieties were investigated by UV-visible and photoluminescence spectroscopy studies in the region 200–700 nm and the electronic properties HOMO and LUMO energies were measured by TD-DFT approach. Moreover, this compound was characterized by thermal analysis between 300 and 500 K which revealing two phase transitions. Finally, X-ray photoelectron spectroscopy (XPS) analysis is reported to determine the degree of oxidation of tin in this compound and analyzing the surface chemistry of (C₅H₁₄N₂)₂[SnCl₆]₂·5H₂O.