Construction of several d metal coordination polymers based on aromatic polycarboxylate and flexible triazole-based ligand

To investigate the effect of organic anions on the coordination frameworks, we synthesized five new complexes, namely, {[Zn₃(μ-OH₂)₂(btc)₂(btx)₃]·4H₂O}_n (1), [Zn(bdc)(btx)]_n (2), {[Ag₈(3,5-pydc)₄(btx)₄]·8H₂O}_n (3), [Ag(2,6-Hpydc)(btx)]_n (4) and [Cd₂(μ₂-OH₂)(2,6-pydc)₂(btx)]_n (5) (H₂bdc = 1,4-benzenedicarboxylic acid; H₃btc = 1,3,5-benzenetricarboxylate; 3,5-H₂pydc = pyridine-3,5-dicarboxylic acid; 2,6-H₂pydc = pyridine-2,6-dicarboxylic acid), which were obtained by the reactions of 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (btx) as main ligand, and several aromatic polycarboxylate as organic anions with different d¹⁰ metal salts. Single crystal structure analysis shows that complexes 1, 3 and 5 possess 3D structures, 2 takes a 2D layer motif, and 4 displays a 1D chain structure. The distinct structures indicate that polycarboxylate anions with the diverse coordination modes and coordination groups can affect the topologies of metal-organic frameworks. In addition, the luminescence measurements reveal that the complexes 1, 2 and 5 exhibit strong fluorescent emissions in the solid state at room temperature.     

Hydrothermal synthesis, crystal structures and photoluminescent properties of four cadmium(II) coordination polymers derived from diphenic acid and auxiliary ligands

Four novel metal coordination polymers, [Cd(dpa)(H₂O)]_n (1), [Cd(dpa)(2,2′-bipy)]_n (2), {[Cd₂(dpa)₂(4,4′-bipy)₃](4,4′-bipy)(H₂O)₂}_n (3) and [Cd(dpa)(bim)₂(H₂O)]}_n (4) (H₂dpa = 2,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, bim = benzimidazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that the 2,4′-diphenic acids acts as bridging ligands, exhibiting rich coordination modes to link metal ions: bis-monodentate, bidentate chelating, chelating/bridging, monoatomic bridging and monodentate modes. In addition, the luminescent properties for compound 1-4 are also investigated in this work.     

Cd(II) coordination polymers constructed from flexible disulfide ligand: Solvothermal syntheses, structures and luminescent properties

Four novel coordination polymers, [Cd(Hdtbb)(dtbb)_0.5(DMF)]_n (1), {[Cd(dtbb)(2,2′-bpy)(H₂O)]·2DMA}_n (2), {[Cd₂(dtbb)₂(1,4-bix)₂]·3DMF}_n (3) and [Cd(dtbb)(1,4-btx)]_n (4) [H₂dtbb = 2,2-dithiobisbenzoic acid, 2,2′-bpy = 2,2′-bipyridine, 1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-btx = 1,4-bis(triazol-1-ylmethyl)benzene] have been synthesized and structurally characterized. Complexes 1 and 2 possess one-dimensional (1D) infinite structures. The structures of complexes 3 and 4 exhibit two dimensional (2D) frameworks, which mainly due to the differences in the bridging modes of dtbb²⁻ ligand and the effect of the N-donor auxiliary ligands. The infrared spectra, thermogravimetric and luminescent properties were also investigated for these compounds.     

Synthesis and characterization of new coordination polymers generated from oxadiazole-containing ligands and IIB metal ions

The coordination chemistry of the oxadiazole-containing rigid bidentate ligands 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (L1) and 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L2) with inorganic IIB metal salts have been investigated. Five new coordination polymers (1-5) were prepared by solution reactions and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Cd(L1)₂(CH₃CN)₂](ClO₄)₂ · (CH₃CN)₂ (1) crystallized in the monoclinic space group P2₁/c, a = 8.4028(5) Å, b = 21.3726(13) Å, c = 10.5617(7) Å, β = 95.1200(10)°, and Z = 2. In the solid state, it adopts an infinite two-dimensional polymeric structural motif with effective cross section of ca. 14.31 × 14.31 Å. Cd(L2)(H₂O)(NO₃)₂ (2) crystallized in the monoclinic space group Ia, a = 7.1203(5) Å, b = 22.2475(15) Å, c = 20.2652(16) Å, β = 90.6080(10)°, and Z = 8. In the solid state, the two Cd(II) centers are connected to each other by L2 ligands and bridging nitrates into a two-dimensional network. [ZnCl₂(L1)] (3) and [HgI₂(L1)] · CH₃CN (4) crystallized in the monoclinic crystal system (3: P2₁/c, a = 5.3702(3) Å, b = 20.4800(11) Å, c = 12.4093(7) Å, β = 94.7930(10)°, and Z = 4; 4: P2/n, a = 17.2733(11) Å, b = 5.2173(3) Å, c = 20.4069(13) Å, β = 102.8690(10)°, and Z = 4). In the solid state, Zn(II) and Hg(II) metal centers are connected to each other by L1 ligands into a zigzag chain motif. Compound 5 (HgBr₂(L2) is different from 3 and 4, monoclinic, P2(1)/n, a = 5.470(4) Å, b = 16.271(13) Å, c = 16.486(12) Å, β = 93.197(15)°, and Z = 4) adopts a novel one-dimensional helical chain motif which resulted from the relative different coordinated orientation of the two N-donors on L2 ligand.     

Two heterometal-organic coordination polymers with chelidamic acid: Syntheses, structures and optical properties

Two heterometal-organic coordination polymers with chelidamic acid ligands, [AgNd(C₇H₃NO₅)₂·3H₂O]_n (1) and 0.75H₃O·[K_0.25Nd(C₇H₃NO₅)₂·3H₂O]·1.75H₂O (2), have been synthesized and characterized by X-ray single-crystal diffraction. The crystal structure of 1 features that chelating units composed of one Nd(III) ion and two tridentate chelating chelidamic acid ligands are connected by the Ag(I) ions to form a one-dimensional chain, further linked by hydrogen bonds into a 3D network. As for 2, discrete independent molecules, made up of Nd(III) and K(I) ions and chelidamic acid ligands, are linked through the hydrogen bonds to form a 1D chain, which are further inter-linked through the complex hydrogen bonds to form a 3D network. The optical properties of 1 and 2 were investigated in terms of fluorescent spectra, which both exhibit good luminescence.     

Syntheses, structures and photoluminescent properties of two zinc(II) coordination polymers based on aromatic polycarboxylate and 1,4-bis(imidazol-1-ylmethyl)benzene

Hydrothermal reaction of Zn(NO₃)₂·6H₂O with benzene-1,2,3-tricarboxylic acid (H₃BTC) or 5-bromoisophthalic acid (H₂BIPA) in the presence of 1,4-bis(imidazol-1-ylmethyl)benzene (bix) produced two novel coordination polymers [Zn₂(OH)(BTC) (bix)]·H₂O (1) and Zn(BIPA)(bix) (2), which were characterized by single-crystal X-ray diffraction, elemental analysis, IR and thermoanalysis. Complex 1 is a novel example of the 2D (3,4)-connected nets with (4²·6)(4²·6³·8) topology. In 2, the BIPA and bix ligands linked the Zn(II) atoms into a deeply corrugated 2D sheet. The corrugated 2D sheets polycatenate each other in a parallel manner yielding a rare 2D → 3D parallel polycatenation net. Thermal and luminescent properties of two complexes have also been investigated.     

Syntheses, structures and luminescence of a series of Cd(II)-containing coordination polymers constructed from a long flexible bis-triazole ligand

Six novel Cd(II) coordination polymers based on 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl (btmb), namely, [Cd(btmb)₂I₂]_n (1), [Cd(btmb)I₂]_n (2), {[Cd(btmb)₂(NO₃)₂]·H₂O}_n (3), {[Cd(btmb)₂(SCN)₂]·3H₂O}_n (4), {[Cd(btmb)(CH₃COO)₂(H₂O)]·CH₃CN}_n (5) and [Cd(btmb)Cl₂(H₂O)]_n (6) have been synthesized by the reactions of btmb with Cd(II) salts in the presence of different anions (I⁻, , NCS⁻, CH₃COO⁻ or Cl⁻) under appropriate reaction conditions. The assemblies of btmb with CdI₂ afford two different structures: two-dimensional (2D) rhombohedral grid layer network structure 1 and 2D layer structure 2 involved with one-dimensional (1D) linear cadmium chains. Treatment of btmb with Cd(NO₃)₂·4H₂O gives rise to a 2D grid network structure 3 which is similar to 1. When the I⁻ or NO₃⁻ anions were replaced by NCS⁻, CH₃COO⁻ or Cl⁻, different 1D coordination polymers 4-6 were obtained, respectively. Polymer 4 displays a 1D double-chain structure, while both polymers 5 and 6 show 1D zigzag chain structures. In addition, the luminescence measurements reveal that polymers 1-6 exhibit different fluorescent emissions in the solid-state at room temperature, which can be attributed to the various coordination environments of Cd(II), solvent molecules and different packing interactions in these polymers.     

Synthesis, crystal structure and luminescent properties of two cadmium thiocyanate coordination polymers with benzylpyridyl cations

Two luminescent Cd(II) complexes [RBzPy][Cd(SCN)₃] for R = Cl (1) and Br (2) have been synthesized and structurally characterized. The Cd atoms are all N3S3 hexa-coordinated with six bridging SCN⁻ and form infinite [Cd(SCN)₃]_∞ polymeric chains. The layer arrangement of the anionic chains was obtained using the larger halogenated benzylpyridyl cations. The luminescent properties of 1 and 2 in the solid state were investigated.     

Two cadmium-thiocyanate coordination polymers with organic cations: Synthesis, crystal structures and luminescent properties

Two new inorganic-organic hybrid polymers [ClBzQl]₂[Cd(SCN)_3.5Br_0.5]·0.25H₂O (1) and [ClBzMePy][Cd(SCN)₃] (2) (ClBzQl = 1-(4′-Cl-benzyl)quinolinium cation and ClBzMePy = 1-(4′-Cl-benzyl)-2-methylpyridinium cation) have been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Crystal structure analyses show that two polymers belong to the monoclinic space group P2/n (1) and P2₁/c (2) with a = 18.548(2) Å, b = 9.526(1) Å, c = 20.689(2) Å, β = 94.008(1)°, V = 3646.6(5) Å³ for 1, and a = 11.195(2) Å, b = 16.415(3) Å, c = 10.751(2) Å, β = 102.930(3)°, V = 1925.7(7) Å³ for 2. The Cd atom exhibits a distorted octahedral coordination geometry for 1 and 2. For 1, a pair of 1,1-μ-SCN⁻ anions and a pair of 1,3-μ-SCN⁻ anions are alternately bridge adjacent Cd centers to form infinite polymeric chains. For 2, adjacent Cd atoms are linked by three 1,3-μ-SCN⁻ anions to form infinite [Cd(SCN)₃⁻]_∞ polymeric chains. The luminescent properties of the two polymers in the solid state at room temperature were investigated.     

Extended structures of three new coordination polymers based on 1,10-phenanthroline derivatives and 1,4-benzenedicarboxylate mixed ligands: Preparation, structural characterization and properties

Three coordination polymers, namely, [Cd(HOIP)₂(1,4-bdc)] (1), [Cu(HOIP)(1,4-bdc)] (2) and [Cu(PDIP)(1,4-bdc)] (3) (HOIP = 2-(4-hydroxylbenzene) imidazo[4,5-f]1,10-phenanthroline, PDIP = 2-(3-pyridine) imidazo[4,5-f]1,10-phenanthroline, and 1,4-bdc = 1,4-benzenedicarboxylate), have been synthesized under the hydrothermal conditions. All complexes have been characterized by elemental analyses, IR and single-crystal X-ray diffraction. Structural analyses reveal that complex 1 possesses infinite one-dimensional (1D) chain bridged by 1,4-bdc ligands, complexes 2 and 3 both exhibit two-dimensional (2D) (4,4) network structures based on dinuclear [Cu₂O₂] units. However, the weak interactions are different in complexes 1-3. Moreover, the thermal properties of all complexes, fluorescence property of 1, and the electrochemical behavior of 3 are also reported in this paper.     

Synthesis, crystal and band structures, and optical and magnetic properties of a 1D copper coordination polymer with chelidamic acid ligand

A 1D coordination polymer, {[Cu₃(C₇H₂NO₅)₂(H₂O)₇]·2(H₂O)}_n (1), has been synthesized and characterized by X-ray single-crystal diffraction. The crystal structure of 1 features that distorted square-pyramidal coordination polyhedra composed of Cu atoms and chelidamic acid ligands are interlinked into a 1D polymer, further linked by hydrogen bonds into a 3D network. The optical properties were investigated in terms of diffuse reflectance and fluorescent spectra, which exhibit strong luminescence. The electronic band structure along with the density of states (DOSs) calculated by the DFT method indicate that compound 1 pose an energy band gap of 1.89 eV and that the origin of the emission band may be mainly ascribed to metal-to-ligand charge transfer (MLCT) where the electrons are transferred from the Cu-3d to O-2p and C-2p states.     

Assembly of two novel cadmium(II) supramolecular architectures constructed from pyridine-functionalized 1,10-phenanthroline ligand

Two novel cadmium(II) coordination polymers [Cd(pyip)(ox)]·H₂O (1) and [Cd₂(pyip)₂(ox)₂·(H₂O)][Cd(pyip)(ox)]·4(H₂O) (2) (pyip = 2-(pyridin-3-yl-1H-imidazo [4,5-f][1,10]phenanthroline, H₂ox = oxalic acid), have been hydrothermal synthesized and characterized by single crystal X-ray diffraction. Compound 1 is 1D zigzag chain, in which oxalate anion as bridging ligand is responsible for the formation of the main framework and pyip as chelating ligand grafts on two sides of the zigzag chain. Compound 2 contains two kinds of independent polymers [Cd₂(pyip)₂(ox)₂(H₂O)] (A) and [Cd(pyip)(ox)] (B) to form an interdigitated 1D + 1D structure, in which polymers A and B are paratactically assembled in an ABCD sequence. The fundamental unit of polymer B in 2 is the same as that in 1. For compounds 1-2, weak interactions, primarily hydrogen bonding and π?π stacking interactions, have greatly influence on the supramolecular motifs recognized in the crystal packing. Especially, the oxalate anions as bridging ligand simultaneously adopt multiform coordination modes in two compounds. In addition, 1 and 2 displayed a strong fluorescent emission in the solid state at room temperature.     

Cation control of dimensionality in isothiocyanate coordination polymers constructed from conformationally flexible 3,3′-bipyridine tethers

Two isothiocyanate coordination polymers constructed from the conformationally flexible tethering ligand 3,3′-bipyridine (3,3′-bpy) and divalent metal cations have been prepared and characterized via single crystal X-ray diffraction, infrared spectroscopy and elemental analysis. [Co(NCS)₂(3,3′-bpy)₂] (1), wherein the isothiocyanate ligands are coordinated in a trans fashion, manifests stacked two-dimensional (2-D) rhomboid grid layered motifs. In contrast, [Ni(NCS)₂(3,3′-bpy)₂] (2) possesses a doubly interpenetrated adamantoid three-dimensional (3-D) network despite the presence of trans isothiocyanate ligands. Thus, a metal cation-based control of coordination polymer dimensionality has been revealed in this system, reflective of different donor dispositions allowed by the conformational flexibility of the exobidentate 3,3′-bpy ligand. The 3-D framework of 2 decomposes at a temperature ∼40 °C higher than the 2-D network of 1.     

Synthesis, structures and properties of alkaline earth metal benzene-1,4-dioxylacetates with three-dimensional hybrid networks

Three novel alkaline earth metal benzene-1,4-dioxylacetates M(L)H₂O (M = Ca, Sr or Ba, L = benzene-1,4-dioxylacetate) with three-dimensional (3D) hybrid frameworks were reported. Both Ca(L)H₂O (1) and Sr(L)H₂O (2) crystallize in the monoclinic space group P2₁/c while Ba(L)H₂O (3) in the monoclinic space group P2₁. As determined by X-ray single-crystal analysis, in these compounds each metal ion is coordinated by eight O atoms: four from different carboxylate groups, two from one carboxylate group, one from the ether oxygen and one from one water molecule. Each L²⁻ ligand coordinates to five alkaline earth metal centers through one of its ether oxygen atoms and two carboxylate groups adopting novel μ₃-η²:η²-bridging and μ₂-η¹:η¹-bridging coordination modes to give rise to a 3D network. The luminescence analysis shows that complexes 1 and 2 exhibit fluorescence in the solid state at room temperature.     

Syntheses, crystal structures and photoluminescences of two (4,4) topological coordination networks derived from the flexible bipyridyl ligands

Two new 2D coordination polymers, [Ag₄(μ-4,4′-bpp)₃(1,3-bdc)₂]_n · 2nH₂O (1) and [Ag(μ-4,4′-bpp)₂ClO₄]_n(2) (4,4′-bpp = 2,2′-bis(4-pyridylmethyleneoxy)-1,1′-biphenylene; 1,3-bdc = 1,3-benzenedicarboxylate) have been synthesized using three-layer diffusion methods. Single-crystal X-ray analyses reveal that they are both extended grid networks of the (4,4) topology. In complex 1, a chain built by Ag(I) centers with T-shaped and linear geometries is further connected by the interesting ligand-unsupported Ag?Ag interactions as well as the conjugated π systems to form an interdigitated 2-D coordination network. The corrugated (4,4) sheets of 2 are packed in the ab planes and stacked along the c direction with the anions occupying the gaps in the squares.     

Synthesis, structures and luminescent properties of novel coordination polymers constructed by lanthanide salts and benzimidazole-5,6-dicarboxylic acid

Two three-dimensional (3D) novel lanthanide complexes with the H₂Lbenzimidazole-5,6-dicarboxylate [Ln₂L₃(H₂O)] [Ln = Eu (1), Tb (2)] and one two-dimensional (2D) novel lanthanide complex [Pr(L)(HL)H₂O]·H₂O (3) were synthesized by hydrothermal reaction at 180 °C and characterized by elemental analysis, infrared spectra and single-crystal X-ray diffraction. The result showed that complexes 1 and 2 are isostructural and build porous 3D networks by L²⁻ groups linking Ln(III) atoms via tetradentate (bridging and bridging) and pentadentate (bridging/chelating and bridging) coordination modes. Complex 3 is a eight-coordinated Pr(III) chain complex, exhibiting a 2D polymeric network with parallel Pr-carboxylate chains along the crystallographic c-axis. In addition, it is found that in these structures, coordination modes of L²⁻ and HL⁻ are versatile and can adopt different conformations according to distinct dimensions of polymeric structures. The photoluminescent properties of 1, 2 and thermogravimetric analyses of the three complexes were discussed in detail.     

Syntheses, structures, and properties of novel one dimensional copper cyanide coordination polymers

Three new one-dimensional copper coordination polymers have been prepared and fully characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and magnetic susceptibility measurements. The structure of [Cu(CN)₂(bpy)] (1) (bpy = 2,2-bipyridyl) (monoclinic P2₁/c, a = 8.9761(7) Å, b = 16.731(1) Å, c = 8.0224(6) Å, β = 114.437(1)°) consists of Cu(II) metal centers coordinated by three cyanide ligands and chelated by one bpy to form the monomers Cu(CN)₃(bpy) with distorted square pyramidal geometry. Each monomer shares two cyanide ligands with two adjacent monomers to form infinite -Cu(II)-CN-Cu(II)-CN-Cu zigzag chains along the c-axis. The one-dimensional structure of [Cu(CN)(bpy)] (2) (hexagonal P3₂, a = 14.4883(6) Å, b = 12.921(1) Å) is built of tetrahedral Cu(CN)₂bpy metal complexes in which Cu(I) metal centers are coordinated by one nitrogen and one carbon from two different CN ligands, and two nitrogens from one bpy. The two CN ligands act as bridging ligands between adjacent monomers to form helical chains along the 3₂ screw axis. The crystal structure of [Cu₂Cl(CN)(bpy)] (3) (orthorhombic Pbca, a = 17.853(2) Å, b = 6.9724 (9) Å, c = 18.7357 (9) Å) consists of two monomers, CuCl₂(CN) and Cu(bpy)(CN) that share a cyanide ligand to form Cu₂Cl₂(CN)(bpy) dimers. The dimers link to each other by sharing Cl ligands leading to the formation of infinite Cu-Cl-Cu chain decorated by the complex Cu(CN)(bpy). Variable-temperature magnetic measurement shows an overall ferromagnetic behavior for compound 1. The magnetic pathway of compound 1 is through the cyanide bridge connecting apical and equatorial positions of adjacent copper (II) ions.     

A growing family: New structures of coordination polymers containing adamantane-shaped phosphorus-nitrogen cage ligands

Two new structurally characterized coordination polymers containing the P₄(NR)₆ ligand system are described. A convenient one-pot synthesis of P₄(NR)₆ (R = benzyl) via reaction of lithiated primary amine with phosphorus trichloride demonstrates an expanded scope for the preparation of this adamantane-type structure. Reactions of P₄(NR)₆ (R = Et, Bn) with cuprous iodide yield different products due to the differences in steric demands of the ligands.     

Five-, seven-, and eight-coordinate Cd(II) coordination polymers built by anthranilic acid derivatives: Synthesis, structures and photoluminescence

Two novel Cd(II) coordination polymers, [(CH₃)₂NH₂]₂[Cd(cma)₂](H₂O) (1) and [Cd₃(bcma)₂(H₂O)](H₂O) (2) (H₂cma = N-(carboxymethyl)-anthranilic acid, H₃bcma = N,N′-bis-(carboxymethyl)-anthranilic acid), have been synthesized under hydrothermal conditions and characterized by X-ray single crystal analysis, IR spectra and TGA. Compound 1 possesses 1D double-stranded chain, which further packs into square channels. Compound 2 consists of a novel 3D framework, which not only possesses unique meniscus-like channels but also contains infinite helical chains. Compound 2 is the first example of Cd(II)-aminopolycarboxylate coordination polymers containing three crystallographically independent Cd(II) centres, in which Cd(1), Cd(2), and Cd(3) present distorted pentagonal bipyramidal, tetragonal antiprismatic, and trigonal bipyramidal coordination geometry, respectively. Both compounds display intense room temperature photoluminescence in the solid state.     

Control of dimensionality through nitrogen donor disposition in divalent metal perchlorate bis(pyridylmethyl)piperazine coordination polymers

Slow diffusion of aqueous solutions of metal perchlorates with alcoholic solutions of bis(4-pyridylmethyl)piperazine (4-bpmp) or bis(3-pyridylmethyl)piperazine (3-bpmp) afforded crystalline coordination polymer phases whose dimensionality and topology is determined largely by the pyridyl nitrogen donor disposition within the imine components. {[M(H₂O)₄(4-bpmp)](ClO₄)₂·4-bpmp·4H₂O}_n (M = Co, 1-Co; M = Zn, 1-Zn) are isostructural, displaying cationic [M(H₂O)₄(4-bpmp)]_n²ⁿ⁺ 1-D coordination polymer chains connected through extensive hydrogen-bonding pathways involving unligated species. In contrast, use of the 3-bpmp isomer generated compounds with formulation of {[M(H₂O)₂(3-bpmp)₂](ClO₄)₂·8H₂O}_n (M = Co, 2-Co; M = Zn, 2-Zn), which manifest achiral 3-fold interpenetrated 6⁶ diamondoid lattices. The zinc derivatives undergo modest blue-violet luminescence on exposure to ultraviolet light.