Metal–Organic Frameworks Constructed from Versatile [WS4Cux]x−2 Units: Micropores in Highly Interpenetrated Systems

Five metal–organic frameworks (MOFs) formed by [WS₄Cu_x]^x?2 secondary building units (SBUs) and multi‐pyridyl ligands are presented. The [WS₄Cu_x]^x?2 SBUs function as network vertexes showing various geometries and connectivities. Compound 1 contains one‐dimensional channels formed in fourfold interpenetrating diamondoid networks with a hexanuclear [WS₄Cu₅]³⁺ unit as SBU, which shows square‐pyramidal geometry and acts as a tetrahedral node. Compound 2 contains brick‐wall‐like layer also with a hexanuclear [WS₄Cu₅]³⁺ unit as SBU. The [WS₄Cu₅]³⁺ unit in 2 is a new type of [WS₄Cu_x]^x?2 cluster unit in which the five Cu⁺ ions are in one plane with the W atom, forming a planar unit. Compound 3 shows a nanotubular structure with a pentanuclear [WS₄Cu₄]²⁺ unit as SBU, which is saddle‐shaped and acts as a tetrahedral node. Compound 4 contains large cages formed between two interpenetrated (10,3)‐a networks also with a pentanuclear [WS₄Cu₄]²⁺ unit acting as a triangular node. The [WS₄Cu₄]²⁺ unit in 4 is isomeric to that in 3 and first observed in a MOF. Compound 5 contains zigzag chains with a tetrahedral [WS₄Cu₃]⁺ unit as SBU, which acts as a V‐shaped connector. The influence of synthesis conditions including temperature, ligand, anions of Cu^I salts, and the ratio of [NH₄]₂WS₄ to Cu^I salt on the formation of these [WS₄Cu_x]^x?2‐based MOFs were also studied. Porous MOF 3 is stable upon removal and exchange of the solvent guests, and when accommodating different solvent molecules, it exhibits specific colors depending on the polarity of incorporated solvent, that is, it shows a rare solvatochromic effect and has interesting prospects in sensing applications.     

Poly[diaqua(μ‐4,4′‐bipyridine‐κ2N:N′)bis(μ‐cyanido‐κ2C:N)bis(cyanido‐κC)nickel(II)copper(II)]: a metal–organic cyanide‐bridged framework

The structure of the title compound, [NiCu(CN)₄(C₁₀H₈N₂)(H₂O)₂]_n or [{Cu(H₂O)₂}(μ‐C₁₀H₈N₂)(μ‐CN)₂{Ni(CN)₂}]_n, was shown to be a metal–organic cyanide‐bridged framework, composed essentially of –Cu–4,4′‐bpy–Cu–4,4′‐bpy–Cu– chains (4,4′‐bpy is 4,4′‐bipyridine) linked by [Ni(CN)₄]²⁻ anions. Both metal atoms sit on special positions; the Cu^II atom occupies an inversion center, while the Ni^II atom of the cyanometallate sits on a twofold axis. The 4,4′‐bpy ligand is also situated about a center of symmetry, located at the center of the bridging C—C bond. The scientific impact of this structure lies in the unique manner in which the framework is built up. The arrangement of the –Cu–4,4′‐bpy–Cu–4,4′‐bpy–Cu– chains, which are mutually perpendicular and non‐intersecting, creates large channels running parallel to the c axis. Within these channels, the [Ni(CN)₄]²⁻ anions coordinate to successive Cu^II atoms, forming zigzag –Cu—N[triple‐bond]C—Ni—C[triple‐bond]N—Cu– chains. In this manner, a three‐dimensional framework structure is constructed. To the authors' knowledge, this arrangement has not been observed in any of the many copper(II)–4,4′‐bipyridine framework complexes synthesized to date. The coordination environment of the Cu^II atom is completed by two water molecules. The framework is further strengthened by O—H...N hydrogen bonds involving the water molecules and the symmetry‐equivalent nonbridging cyanide N atoms.     

Route to a family of robust, non-interpenetrated metal-organic frameworks with pto-like topology

A combination of topological rules and quantum chemical calculations has facilitated the development of a rational metal–organic framework (MOF) synthetic strategy using the tritopic benzene‐1,3,5‐tribenzoate (btb) linker and a neutral cross‐linker 4,4′‐bipyridine (bipy). A series of new compounds, namely [M₂(bipy)]₃(btb)₄ (DUT‐23(M), M=Zn, Co, Cu, Ni), [Cu₂(bisqui)_0.5]₃(btb)₄ (DUT‐24, bisqui=diethyl (R,S)‐4,4′‐biquinoline‐3,3′‐dicarboxylate), [Cu₂(py)_1.5(H₂O)_0.5]₃(btb)₄ (DUT‐33, py=pyridine), and [Cu₂(H₂O)₂]₃(btb)₄ (DUT‐34), with high specific surface areas and pore volumes (up to 2.03 m³ g^?1 for DUT‐23(Co)) were synthesized. For DUT‐23(Co), excess storage capacities were determined for methane (268 mg g^?1 at 100 bar and 298 K), hydrogen (74 mg g^?1 at 40 bar and 77 K), and n‐butane (99 mg g^?1at 293 K). DUT‐34 is a non‐cross‐linked version of DUT‐23 (non‐interpenetrated pendant to MOF‐14) that possesses open metal sites and can therefore be used as a catalyst. The accessibility of the pores in DUT‐34 to potential substrate molecules was proven by liquid phase adsorption. By exchanging the N,N donor 4,4′‐bipyridine with a substituted racemic biquinoline, DUT‐24 was obtained. This opens a route to the synthesis of a chiral compound, which could be interesting for enantioselective separation.     

Heterobimetallic Cluster-Based Coordination Polymers: Assembly,Structures and Third-Order Nonlinear Optical Properties

Reactions of (NH₄)₂WS₄ with CuCN, CuCN/1,2-bis(4-pyridyl)propane (bppa) or [Cu(MeCN)₄]PF₆/bppa under different reaction conditions afforded a set of two- or three-dimensional W/Cu/S cluster-based coordination polymers including {[Et₄N]₂[WS₄Cu₄(μ-CN)₂(μ-I)₂]}_n ( 1 ), [WS₄Cu₄(μ-CN)₂(bppa)₂]_n ( 2 ) and {[WS₄Cu₄(bppa)₄](PF₆)₂}_n ( 3 ), respectively. Compound 2 can be readily formed from reaction of 1 with bppa under solvothermal conditions. Compounds 1 and 2 feature two-dimensional networks with a “sql” topology, while 3 possesses a two-fold interpenetrated three-dimensional net with a rare “reo” topology. Compounds 1 – 3 in DMF exhibited different third-order nonlinear optical responses, and they all showed a reverse saturable absorption while 2 held a strong self-focusing effect.     

Supramolecular Stuctures from Mononuclear,Binuclear and 2D Net of Copper(II) Complexes with 6‐Hydroxypicolinic Acid

First examples of transition metal complexes with HpicOH [Cu(picOH)₂(H₂O)₂] ( 1 ), [Cu(picO)(2,2′‐bpy)]·2H₂O ( 2 ), [Cu(picO)(4,4′‐bpy)_0.5(H₂O)]_n ( 3 ), and [Cu(picO)(bpe)_0.5(H₂O)]_n ( 4 ) (HpicOH = 6‐hydroxy‐picolinic acid; 2,2′‐bpy = 2,2′‐bipyridine; 4,4′‐bpy = 4,4′‐bipyridine; bpe = 1,2‐bis(4‐pyridyl)ethane) have been synthesized and characterized by single‐crystal X‐ray diffraction. The results show that HpicOH ligand can be in the enol or ketonic form, and adopts different coordination modes under different pH value of the reaction mixture. In complex 1 , HpicOH ligand is in the enol form and adopts a bidentate mode. While in complexes 2 – 4 , as the pH rises, HpicOH ligand becomes in the ketonic form and adopts a tridentate mode. The coordination modes in complexes 1 – 4 have not been reported before. Because of the introduction of the terminal ligands 2,2′‐bpy, complex 2 is of binuclear species; whereas in complexes 3 and 4 , picO ligands together with bridging ligands 4,4′‐bpy and bpe connect Cu^II ions to form 2D nets with (12³)₂(12)₃ topology.     

(4,4′‐Bipyridine)mercury(II) Coordination Polymers,Syntheses, and Structures

Mercury(II) complexes with 4,4′‐bipyridine (4,4′‐bipy) ligand were synthesized and characterized by elemental analysis, and IR, ¹H‐ and ¹³C‐NMR spectroscopy. The structures of the complexes [Hg₃(4,4′‐bipy)₂(CH₃COO)₂(SCN)₄]_n ( 1 ), [Hg₅(4,4′‐bipy)₅(SCN)₁₀]_n ( 2 ), [Hg₂(4,4′‐bipy)₂(CH₃COO)₂]_n(ClO₄)_2n ( 3 ), and [Hg(4,4′‐bipy)I₂]_n ( 4 ) were determined by X‐ray crystallography. The single‐crystal X‐ray data show that 2 and 4 are one‐dimensional zigzag polymers with four‐coordinate Hg‐atoms, whereas 1 is a one‐dimensional helical chain with two four‐coordinate and one six‐coordinate Hg‐atom. Complex 3 is a two‐dimensional polymer with a five‐coordinate Hg‐atom. These results show the capacity of the Hg‐ion to act as a soft acid that is capable to form compounds with coordination numbers four, five, and six and consequently to produce different forms of coordination polymers, containing one‐ and two‐dimensional networks.     

In‐ and Out‐of‐Cavity Interactions by Modulating the Size of Ruthenium Metallarectangles

Cationic (arene)ruthenium‐based tetranuclear complexes of the general formula [Ru₄(η⁶‐p‐cymene)₄(μ‐N∩N)₂(μ‐OO∩OO)₂]⁴⁺ were obtained from the dinuclear (arene)ruthenium complexes [Ru₂(η⁶‐p‐cymene)₂(μ‐OO∩OO)₂Cl₂] (p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, OO∩OO=5,8‐dihydroxy‐1,4‐naphthoquinonato(2?), 9,10‐dihydroxy‐1,4‐anthraquinonato(2?), or 6,11‐dihydroxynaphthacene‐5,12‐dionato(2?)) by reaction with pyrazine or bipyridine linkers (N∩N=pyrazine, 4,4′‐bipyridine, 4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine]) in the presence of silver trifluoromethanesulfonate (CF₃SO₃Ag) (Scheme). All complexes 4 – 12 were isolated in good yield as CF₃SO salts, and characterized by NMR and IR spectroscopy. The host–guest properties of the metallarectangles incorporating 4,4′‐bipyridine and (4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine] linkers were studied in solution by means of multiple NMR experiments (1D, ROESY, and DOSY). The largest metallarectangles 10 – 12 incorporating (4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine] linkers are able to host an anthracene, pyrene, perylene, or coronene molecule in their cavity, while the medium‐size metallarectangles 7 – 9 incorporating 4,4′‐bipyridine linkers are only able to encapsulate anthracene. However, out‐of‐cavity interactions are observed between these 4,4′‐bipyridine‐containing rectangles and pyrene, perylene, or coronene. In contrast, the small pyrazine‐containing metallarectangles 4 – 6 show no interaction in solution with this series of planar aromatic molecules.     

Diamond‐ and Graphite‐Like Octacyanometalate‐Based Polymers Induced by Metal Ions

By using cyclohexane‐1,2‐diamine (chxn), Ni(ClO₄)₂ ? 6H₂O and Na₃[Mo(CN)₈] ? 4H₂O, a 3D diamond‐like polymer {[Ni^II(chxn)₂]₂[Mo^IV(CN)₈] ? 8H₂O}_n ( 1 ) was synthesised, whereas the reaction of chxn and Cu(ClO₄)₂ ? 6H₂O with Na₃[M^V(CN)₈] ? 4H₂O (M=Mo, W) afforded two isomorphous graphite‐like complexes {[Cu^II(chxn)₂]₃[Mo^V(CN)₈]₂ ? 2H₂O}_n ( 2 ) and {[Cu^II(chxn)₂]₃[W^V(CN)₈]₂ ? 2H₂O}_n ( 3 ). When the same synthetic procedure was employed, but replacing Na₃[Mo(CN)₈] ? 4H₂O by (Bu₃NH)₃[Mo(CN)₈] ? 4H₂O (Bu₃N=tributylamine), {[Cu^II(chxn)₂Mo^IV(CN)₈][Cu^II(chxn)₂] ? 2H₂O}_n ( 4 ) was obtained. Single‐crystal X‐ray diffraction analyses showed that the framework of 4 is similar to 2 and 3 , except that a discrete [Cu(chxn)₂]²⁺ moiety in 4 possesses large channels of parallel adjacent layers. The experimental results showed that in this system, the diamond‐ or graphite‐like framework was strongly influenced by the inducement of metal ions. The magnetic properties illustrate that the diamagnetic [Mo^IV(CN)₈] bridges mediate very weak antiferromagnetic coupling between the Ni^II ions in 1 , but lead to the paramagnetic behaviour in 4 because [Mo^IV(CN)₈] weakly coordinates to the Cu^II ions. The magnetic investigations of 2 and 3 indicate the presence of ferromagnetic coupling between the Cu^II and W^V/Mo^V ions, and the more diffuse 5d orbitals lead to a stronger magnetic coupling interaction between the W^V and Cu^II ions than between the Mo^V and Cu^II ions.     

Auxilary Ligand Directed Zinc(II) Metal‐Organic Frameworks with Different Topological Networks

By altering auxiliary N‐donor ligands, two Zn^II compounds, [Zn₃(HL)₂(4,4′‐bipy)₃]_n ( 1 ) and [Zn₄(L)₂(bpp)]_n ( 2 ) (H₄L = 3‐(2′,4′‐dicarboxylphenoxy)phthalic acid, 4,4′‐bipy = 4,4′‐bipyridine, and bpp = 1,3‐bis(4‐pyridyl)propane), were obtained under hydrothermal conditions. Structural analyses revealed that compound 1 features a trinodal (3,4,4)‐connected 3D topological framework, and compound 2 displays a (3,8)‐connected 3D pillar‐layered framework with a tfz‐d topology. Furthermore, the thermal stabilities and the luminescent properties of compounds 1 and 2 were investigated.     

Synthesis,Structure, and Magnetic Properties of a Copper(II) Metal‐Organic Framework with Biphenyl‐2,2′,4,4′‐tetracarboxylic Acid

The 2D Cu^II metal‐organic framework [Cu₂(bptc)(H₂O)₄]_n · 4nH₂O ( 1 ) (H₄bptc = biphenyl‐2,2′,4,4′‐tetracarboxylic acid) was hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction and magnetic measurements. In the structure, bptc^4– serves as a twisted Π‐shaped organic building block to connect paddlewheel [Cu₂(COO)₄] dinuclear units and mononuclear units through 2‐/2′‐carboxylate and 4‐/4′‐carboxylate, respectively. According to the magnetic analysis using a dimer‐plus‐monomer model, strong antiferromagnetic coupling is operative within the dinuclear unit (J = –311 cm^–1 based on H = –J S ₁ S ₂), and the compound behaves like a mononuclear molecule at low temperature.     

Poly­[[di­aqua­tris(μ6‐benzene‐1,2,4,5‐tetra­carboxyl­ato)­tris(μ2‐4,4′‐bi­pyridine)­hexacopper(II)] dihydrate]

The hydro­thermal reaction of an aqueous solution of Cu(CH₃COO)₂·H₂O, 1,2,4,5‐benzene­tetra­carboxylic acid and 4,4′‐bi­pyridine gave rise to the interesting title three‐dimensional polymer {[Cu₆(btec)₃(4,4′‐bpy)₃(H₂O)₂]·2H₂O}_n (btec is 1,2,4,5‐benzene­tetra­carboxyl­ate, C₁₀H₂O₈⁴⁻, and 4,4′‐bpy is 4,4′‐bi­pyridine, C₁₀H₈N₂), in which each btec ligand links six copper(II) cations into a lamellar [Cu₆(btec)₃(H₂O)₂]_n sub­polymer framework. There are two distinct diamine units and two distinct carboxylate units, with one of each lying across an inversion centre.     

Post‐Synthetic Monovalent Central‐Metal Exchange,Specific I2 Sensing,and Polymerization of a Catalytic [3×3] Grid of [CuII5CuI4L6]⋅(I)2⋅13 H2O

From a predesigned grid, [Cu^II₅Cu^I₄L₆] ? (I)₂ ? 13 H₂O ( 1 ), in which LH₂ was a pyrazinyl‐triazolyl‐2,6‐substituted pyridine, we successfully synthesized an extended 3D complex, ¹_∞[{Cu^II₅Cu^I₈L₆}{μ‐[Cu^I₃(CN)₆]}₂ ? 2 CH₃‐ CN] ( 2 ), that displayed unprecedented coexistence of all the five known coordination geometries of copper. Grid 1 displayed monovalent central metal exchange (CME) of Cu^I for Ag^I for the first time, as well as the formation of tri‐iodide in the crystalline state. These systems were investigated for their magnetic properties. Remarkably, grid 1 showed much higher catalytic activity than the Ag‐exchanged product for synthesis of a substituted triazole, 1‐benzyl‐4‐phenyl‐1H‐1,2,3‐triazole.     

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.     

Poly[diaquabis(μ‐4,4′‐bipyridine‐κ2N:N′)bis(ethane‐1,2‐diol)di‐μ‐sulfato‐dicopper(II)]

The title compound, [Cu₂(SO₄)₂(C₁₀H₈N₂)₂(C₂H₆O₂)₂(H₂O)₂]_n, contains two crystallographically unique Cu^II centres, each lying on a twofold axis and having a slightly distorted octahedral environment. One Cu^II centre is coordinated by two bridging 4,4′‐bipyridine (4,4′‐bipy) ligands, two sulfate anions and two aqua ligands. The second is surrounded by two 4,4′‐bipy N atoms and four O atoms, two from bridging sulfate anions and two from ethane‐1,2‐diol ligands. The sulfate anion bridges adjacent Cu^II centres, leading to the formation of linear ...Cu1–Cu2–Cu1–Cu2... chains. Adjacent chains are further bridged by 4,4′‐bipy ligands, which are also located on the twofold axis, resulting in a two‐dimensional layered polymer. In the crystal structure, extensive O—H...O hydrogen‐bonding interactions between water molecules, ethane‐1,2‐diol molecules and sulfate anions lead to the formation of a three‐dimensional supramolecular network structure.     

Synthesis and Structural Characterization of Six Pentanuclear and Tetranuclear Mo/W‐Cu‐S Clusters with Bis(diphenylphosphanyl) Methane

Six heterothiometalic clusters, namely, [WS₄Cu₄(dppm)₄](ClO₄)₂ · 2DMF · MeCN ( 1 ), [MoS₄Cu₄(dppm)₄](NO₃)₂ · MeCN ( 2 ) [MoS₄Cu₃(dppm)₃](ClO₄) · 4H₂O ( 3 ), [WS₄Cu₃(dppm)₃](NO₃) · 4H₂O ( 4 ), [WS₄Cu₃(dppm)₃]SCN · CH₂Cl₂ ( 5 ), and [WS₄Cu₃(dppm)₃]I · CH₂Cl₂ ( 6 ) [dppm = bis (diphenylphosphanyl)methane] were synthesized. Compounds 1 – 4 were obtained by the reactions of (NH₄)₂MS₄ (M = Mo, W) with [Cu₂(μ₂‐dppm)₂(MeCN)₂(ClO₄)₂] {or [Cu(dppm)(NO₃)]₂} in the presence of 1,10‐phen in mixed solvent (CH₃CN/CH₂Cl₂/DMF for 1 and 2 , CH₂Cl₂/CH₃OH/DMF for 3 and 4 . Compounds 5 and 6 were obtained by one‐pot reactions of (NH₄)₂WS₄ with dppm and CuSCN (or CuI) in CH₂Cl₂/CH₃OH. These clusters were characterized by single‐crystal X‐ray diffraction as well as IR, ¹H NMR, and ³¹P NMR spectroscopy. Structure analysis showed that compounds 1 and 2 are “saddle‐shaped” pentanuclear cationic clusters, whereas compounds 3 – 6 are “flywheel‐shaped” tetranuclear cationic clusters. In 1 and 2 , the MS₄^2– unit (M = W, Mo) is coordinated by four copper atoms, which are further bridged by four dppm molecules. In compounds 3 – 6 , the MS₄^2– unit is coordinated by three copper atoms and each copper atom is bridged by three dppm ligands.     

Poly[tetraamminecopper(II) bis[tris(μ2‐cyanido‐κ2C,N)dicuprate(I)]]: a unique CuI–CuII mixed‐valence complex containing anionic cuprous cyanide layers and [Cu(NH3)4]2+ cations

The title compound, {[Cu(NH₃)₄][Cu(CN)₃]₂}_n, features a Cu^I–Cu^II mixed‐valence CuCN framework based on {[Cu₂(CN)₃]⁻}_n anionic layers and [Cu(NH₃)₄]²⁺ cations. The asymmetric unit contains two different Cu^I ions and one Cu^II ion which lies on a centre of inversion. Each Cu^I ion is coordinated to three cyanide ligands with a distorted trigonal–planar geometry, while the Cu^II ion is ligated by four ammine ligands, with a distorted square‐planar coordination geometry. The interlinkage between Cu^I ions and cyanide bridges produces a honeycomb‐like {[Cu₂(CN)₃]⁻}_n anionic layer containing 18‐membered planar [Cu(CN)]₆ metallocycles. A [Cu(NH₃)₄]²⁺ cation fills each metallocyclic cavity within pairs of exactly superimposed {[Cu₂(CN)₃]⁻}_n anionic layers, but there are no cations between the layers of adjacent pairs, which are offset. Pairs of N—H...N hydrogen‐bonding interactions link the N—H groups of the ammine ligands to the N atoms of cyanide ligands.     

A novel tetrazolate‐ and cyanide‐bridged three‐dimensional heterometallic coordination polymer: crystal structure,thermal stability and magnetic properties

By using environmentally friendly K₃[Co(CN)₆] as a cyanide source, the solvothermal reaction of CuCl₂ and tetrazole (Htta) led to a novel tetrazolate‐ and cyanide‐bridged three‐dimensional heterometallic Cu^II–Co^III complex, namely poly[[hexa‐μ₂‐cyanido‐κ¹²C :N‐pentakis(μ₃‐tetrazolato‐κ³N ¹:N ²:N ⁴)cobalt(III)tetracopper(II)] monohydrate], {[Co^IIICu^II₄(CHN₄)₅(CN)₆]·H₂O}_n , (I). The crystal structure analysis reveals that it is the first example of a (6,8,8)‐connected three‐dimensional framework with a unique topology, constructed from anionic [Co(CN)₆]³⁻ and cationic [(Cu1)₂(tta)₂]²⁺ and [(Cu2Cu3)(tta)₃]⁺ units through μ₂‐cyanide and μ₃‐tetrazolate linkers. The compound was further characterized by thermal analysis, vibrational spectroscopy (FT–IR), scanning electron microscopy/energy‐dispersive X‐ray spectroscopy (SEM–EDS) and magnetic measurements. The magnetic investigation indicates that the complex exhibits antiferromagnetic coupling between adjacent Cu^II cations.     

Topological identification of the first uninodal 8‐connected lsz MOF built from 2,2′‐difluorobiphenyl‐4,4′‐dicarboxylate pillars and cadmium(II)–triazolate layers

Using polynuclear metal clusters as nodes, many high‐symmetry high‐connectivity nets, like 8‐connnected bcu and 12‐connected fcu , have been attained in metal–organic frameworks (MOFs). However, construction of low‐symmetry high‐connected MOFs with a novel topology still remains a big challenge. For example, a uninodal 8‐connected lsz network, observed in inorganic ZrSiO₄, has not been topologically identified in MOFs. Using 2,2′‐difluorobiphenyl‐4,4′‐dicarboxylic acid (H₂L) as a new linker and 1,2,4‐triazole (Htrz) as a coligand, a novel three‐dimensional Cd^II–MOF, namely poly[tetrakis(μ₄‐2,2′‐difluorobiphenyl‐4,4′‐dicarboxylato‐κ⁵O¹,O^1′:O^1′:O⁴:O^4′)tetrakis(N,N‐dimethylformamide‐κO)tetrakis(μ₃‐1,2,4‐triazolato‐κ³N¹:N²:N⁴)hexacadmium(II)], [Cd₆(C₁₄H₆F₂O₄)₄(C₂H₂N₃)₄(C₃H₇NO)₄]_n, (I), has been prepared. Single‐crystal structure analysis indicates that six different Cd^II ions co‐exist in (I) and each Cd^II ion displays a distorted [CdO₄N₂] octahedral geometry with four equatorial O atoms and two axial N atoms. Three Cd^II ions are connected by four carboxylate groups and four trz⁻ ligands to form a linear trinuclear [Cd₃(COO)₄(trz)₄] cluster, as do the other three Cd^II ions. Two Cd₃ clusters are linked by trz⁻ ligands in a μ_1,2,4‐bridging mode to produce a two‐dimensional Cd^II–triazolate layer with (6,3) topology in the ab plane. These two‐dimensional layers are further pillared by the L²⁻ ligands along the c axis to generate a complicated three‐dimensional framework. Topologically, regarding the Cd₃ cluster as an 8‐connected node, the whole architecture of (I) is a uninodal 8‐connected lsz framework with the Schläfli symbol (4²²·6⁶). Complex (I) was further characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction, thermogravimetric analysis and a photoluminescence study. MOF (I) has a high thermal and water stability.     

catena‐Poly[bis(μ‐2,2′‐bipyridin‐6‐olato)‐κ3N,N′:O;O:N,N′‐dicopper(I,II) [[tetrafluoridoniobium(V)]‐μ‐oxido]]

A novel copper–niobium oxyfluoride, {[Cu₂(C₁₀H₇N₂O)₂][NbOF₄]}_n, has been synthesized by a hydrothermal method and characterized by elemental analysis, EDS, IR, XPS and single‐crystal X‐ray diffraction. The structural unit consists of one C₂‐symmetric [NbOF₄]⁻ anion and one centrosymmetric coordinated [Cu₂(obpy)₂]⁺ cation (obpy is 2,2′‐bipyridin‐6‐olate). In the [NbOF₄]⁻ anion, each Nb^V metal centre is five‐coordinated by four F atoms and one O atom in the first coordination shell, forming a square‐pyramidal coordination geometry. These square pyramids are then further connected to each other via trans O atoms [Nb—O = 2.187 (3) Å], forming an infinite linear {[NbOF₄]⁻}_n polyanion. In the coordinated [Cu₂(obpy)₂]⁺ cation, the oxidation state of each Cu site is disordered, which is confirmed by the XPS results. The disordered Cu sites are coordinated by two N atoms and one O atom from two different obpy ligands. The [NbOF₄]⁻ and [Cu₂(obpy)₂]⁺ units are assembled via weak C—H...F hydrogen bonds, resulting in the formation of a three‐dimensional supramolecular structure. π–π stacking interactions between the pyridine rings [centroid–centroid distance = 3.610 (2) Å] may further stabilize the crystal structure.     

Synthesis,Crystal Structure and Third‐order Nonlinear Optical Properties of Nest‐shaped Cluster [CuBr(bpy)2] [MoOS3Cu3‐Br2(bpy)]

Nest‐shaped cluster [CuBr(bpy)₂][MoOS₃Cu3Br₂(bpy)] was synthesized by the treatment of (NH₄)₂ MOO₂S₂, CuBr and Et₄NBr with bpy (2,2′‐bipyridyl) in CH₃CN. Its structure has been characterized by X‐ray diffraction; monoclinic, space group P2₁/n ‐ with a = l.0092(4), b = 2.6347(7), c = 1.4087(3) nm, β = 91.744(9)°, V = 3.7438 nm³, Z=4, and final R = 0.051, R_w = 0.053. It consists of two parts: nest‐shaped structural unit [MoOS₃Cu₃Br₂(bpy)] and complex ion [CuBr(bpy)²]⁺. We determined its third‐order nonlinear optical (NLO) properties with a 7‐ns pulsed laser at 532 nm. The duster exhibits strong NLO refractive behavior, its third‐order susceptibility χ⁽³⁾ was calculated to be 2.7 · 10^?11 esu in a 7.8 · 10^?4 g/cm³ DMF solution. The value is comparable to those of inorganic dusters.