Hydrothermal synthesis and characterization of a new 1-D polymeric lanthanum ethylenediaminetetraacetate with less metal-aqua coordination: {[La(EDTA)(H2O)]2}n

A new lanthanum ethylenediaminetetraacetate (EDTA) coordination polymer, {[La(EDTA)(H₂O)]₂}_n (EDTA³⁻ = [(CH₂N)₂(CH₂COOH)(CH₂COO⁻)₃]), was hydrothermally prepared from LaCl₃ solution and ethylenediaminetetracetic acid at 448 K. The compound was characterized by elemental analysis, FTIR, TG-DTA, and X-ray crystallography. The structure consists of ladder-like chains of [La(EDTA)(H₂O)]₂ dimers bridged by O-C-O groups. Hydrothermal method successfully reduced the high number of La-aqua coordinations in known lanthanum EDTA to one giving rise to relatively compact structure. It has high thermal stability up to 550 K. Every EDTA ligand with COOH group is involved in eight La-O(N) bonds to three nine-coordinated La centers.     

Hydrothermal synthesis, structural determination, and thermal properties of 2-D cobalt- and nickel-based coordination polymers incorporating pendant-arm 3-pyridinecarboxylate ligands

Hydrothermal synthesis has afforded a family of four coordination polymers containing divalent nickel or cobalt and pendant-arm pyridylcarboxylate ligands. Utilizing 3-pyridylacetic acid and appropriate metal precursors produced [M(3-pyrac)₂(H₂O)₂] phases (M = Co (1); M = Ni (2)), while 3-pyridylpropionic acid generated [M(3-pyrprop)₂(H₂O)₂] coordination polymers (M = Co (3); M = Ni (4)). Single crystal X-ray diffraction revealed that 1-4 all display discrete 2-D layers with (4,4)-topology, anchored via bridging 3-pyridylcarboxylate ligands bearing monodentate carboxylate termini. Intralamellar hydrogen bonding between the aquo ligands and unligated carboxylate oxygen atoms is observed within 1-4. The pseudo 3-D structures of 1-4 are further assembled via stacking of individual neutral layers by interlayer hydrogen bonding. Thermal properties are also discussed.     

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.     

Metal-directed assembly of 1-D and 2-D coordination polymers with fluconazole and dicyanamide co-ligand

The coordination chemistry of a flexible poly(triazolyl)alkane derivative, fluconazole (HFlu), with a series of transition metal ions and dicyanamide (dca) anionic co-ligand has been explored to afford six new metal-organic coordination polymers. Complexes [M(HFlu)₂(dca)₂]_n (M = Mn^II for 1, Fe^II for 2, Co^II for 3, Zn^II for 5, and Cd^II for 6) have the isostructural 1-D double-chain array via bridging fluconazole, whereas [Cu₃(Flu)₂(dca)₄(CH₃OH)₂]_n (4) shows an unusual 2-D layered metal-organic framework with dimeric Cu^II subunits. Notably, both types of coordination patterns are extended into distinct 3-D supramolecular networks via hydrogen-bonding interactions. This result indicates that the choice of metal ion has a significant effect on these polymeric structures as well as the binding modes of the ligands, which is discussed in detail. The Zn^II and Cd^II complexes 5 and 6 display similar fluorescent emissions at 260 nm in the solid state, which essentially are intraligand transitions.     

Hydrothermal syntheses, crystal structures and characterizations of three new copper coordination polymers

Three new copper complexes, [Cu^IICu^I(ip)(ipH)(4,4′-bipy)_3/2]_n (1), [Cu(ip)(4,4′-bipy)]_n · 3nH₂O (2), and [Cu(ipH)₂(4,4′-bipy)]_n (3), have been hydrothermally synthesized by the reaction of Cu(NO₃)₂ · 3H₂O with isophthalic acid (ipH₂) and 4,4′-bipyridine (4,4′-bipy) under different reaction conditions. Complex 1, a mixed-valence copper(I,II) complex, exhibits a 2-D interpenetrating grid framework, in which five-coordinated Cu^II and three-coordinated Cu^I environments are established. The oxidation states of center Cu atoms have been confirmed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR). Complex 2 features a 2-D box-like bilayer architecture, in which Cu^II atoms are linked by ip ligands to form a 1-D double-chain and the resulting chains are further strutted by the 4,4′-bipy ligands. In complex 3, two bridging 4,4′-bipy ligands and two terminal ipH ligands confine the Cu^II center in a square plane coordination geometry. The whole molecule of 3 was arranged into a 1-D linear chain structure. Additionally, the thermogravimetric analyses (TGA) for complexes 1-3 are also discussed in this paper.     

A novel three-dimensional metal-organic network, Zn2(btec)(pipz)(H2O) (btec=1,2,4,5-benzenetetracarboxylate, pipz=piperazine), with blue fluorescent emission

A novel metal-organic compound Zn₂(btec)(pipz)(H₂O) (1) (btec=1,2,4,5-benzenetetracarboxylate, pipz=piperazine ) has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, TG analysis, luminescent spectrum and single-crystal X-ray diffraction. The title compound exhibits a novel three-dimensional network, which consists of two-dimensional wave-like sheets linked by zinc metal centers and piperazine. Compound 1 provides the first coordination network structure constructed together by bridging piperazine and btec mixed ligand. The study of the physical properties of 1 demonstrates that it exhibits a fluorescent emission in solid state at room temperature.     

Synthesis and characterization of a novel three-dimensional photoluminescent coordination polymer generated from unsymmetrically bridging ligand

A novel three-dimensional metal-organic coordination polymer, [Zn₂(HBTC)₂(H₂O)₃]_n (1) (BTC=1,2,4-benzenetricarboxylate), has been prepared by aqueous solution reaction of Zn(NO₃)₂ · 6H₂O and BTC at moderate temperature and characterized by IR, TGA and single-crystal X-ray diffraction analysis. The three-dimensional architecture of 1 not only possesses rectangular cavities but also has ordered one-dimensional straight channels. Furthermore, compound 1 shows intense photoluminescent property at room temperature.     

Solvothermal synthesis, crystal structure and properties of a novel 1-D organic amine templated holmium sulfate

The first organic amine templated 1-D holmium sulfate [C₆N₄H₂₂]_1.5[Ho₂(SO₄)₆ · H₂O] 1 has been synthesized solvothermally and structurally characterized by single-crystal X-ray diffraction, powder XRD, IR, TGA and ICP. The structure of framework compound 1 is constructed from the [-Ho-O-S-O-]_n chains. Two types of [-Ho-O-S-O-]_n chains connect each other by sharing the bridging groups to generate a Ho-O-S ladder, while the adjacent ladders are connected by μ₃-O atoms to form a novel triple ladders. The fully protonated triethylenetetraamine molecules are situated between the ladders, and involved in the hydrogen bonding with oxygen atoms of inorganic framework.     

Hydrothermal synthesis and characterization of two 2-D lanthanide-2,2′-bipyridine-3,3′-dicarboxylate coordination polymers based on zigzag chains

Two lanthanide coordination polymers, {[La₂(bpdc)₃(H₂O)₄]·(H₂O)₄}_n (1) and {[Sm₂(bpdc)₃(H₂O)₂]·(H₂O)₅}_n (2) (H₂bpdc = 2,2′-bipyridine-3,3′-dicarboxylic acid) have been obtained by hydrothermal synthesis. Single-crystal X-ray diffraction shows that 1 and 2 are two-dimensional network structures based on the zigzag chains which are linked by bpdc ligands, forming the first examples of binary lanthanide polymers with bpdc. It is unprecedented that the adjacent zigzag chains are symmetrical in mirror images with the arraying form of ?ABAB?. In 1 and 2, lanthanide ion are all nine-coordinate and bpdc ligands exhibit different kinds of coordination modes. The 1-D infinite water chain in 1 and pentameric water ring in 2 have been found between lattice water molecules. Thermo-gravimetric analyses of 1 and 2 display considerable thermal stability. Photoluminescent properties of 1 and 2 are discussed.     

Hydrothermal syntheses, structural characterizations and magnetic properties of cobalt(II) and manganese(II) coordination polymeric complexes containing pyrazinecarboxylate ligand

Two novel coordination polymeric complexes [Co(pzca)₂(H₂O)]_n (1) and [Mn(pzca)₂]_n (2) (pzca=2-pyrazinecarboxylate) have been synthesized by hydrothermal reaction of M(CH₃COO)₂·4H₂O (M=Co, Mn) and 2-pyrazinecarboxylic acid. The complex 1 displays an infinite zigzag chain structure in which each cobalt(II) center was coordinated by three nitrogen and three oxygen atoms to generate a CoN₃O₃ octahedral geometry. The existence of hydrogen bond leads to the formation of the interpenetrating stacking structure. Complex 2 indicates a two-dimensional layer structure through the linkage of bridging oxygen atom of pzca ligand. Each Mn(II) center exhibits a distorted octahedral coordination environment with four oxygen atoms and two nitrogen atoms. The distances of adjacent Mn(II) atoms are 3.503 and 5.654 Å, respectively. The magnetic property analyses reveal that both complexes show weak antiferromagnetic exchange interactions between the metal centers.     

Hydrothermal synthesis and crystal structures of two lanthanide coordination polymers with novel tetradentate-coordinated perchlorates

Two new 3D lanthanide coordination polymers {[Ln(C₂O₄)(ClO₄)(H₂O)] · Cl}_n [Ln = Pr (1) and Nd (2)] have been synthesized by hydrothermal reactions and characterized by elemental analysis, X-ray single-crystal analyses, IR and Raman spectroscopy. X-ray crystal structure analyses reveal that compounds 1 and 2 are isostructural and crystallized in the space group P2₁/c. A 1D zigzag chains formed by oxalate ligands in μ₂-mode to bridge Ln(III) atoms present in the two complexes and the adjacent zigzag chains were further connected by μ₃-η¹:η¹:η¹:η¹ fashion of into a 3D framework with ordered 1D channels, in which uncoordinated Cl⁻ anions are located as counterions. In addition, the IR and Raman spectrum further confirm the presence of tetradentate-coordinated perchlorates.     

Syntheses, structures and photoluminescence properties of cadmium(II) and zinc(II) complexes with pyridinylcarboxamide-containing ligand

Four new coordination complexes [Cd(DPBA-3)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cd(DPBA-3)(DMF)(NO₃)₂]·DMF (2), [Cd₃(DPBA-3)₂(SCN)₆]·2DMF·4H₂O (3) and [Zn(DPBA-3)(SCN)₂] (4) [DPBA-3 = N,N′-di(pyridin-3-yl)pyridine-3,5-dicarboxamide] have been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. Complexes 1, 3 and 4 exhibit three different types of one-dimensional (1D) chain structures constructed by the metal ions and DPBA-3 ligands, and the Cd(II)-DPBA-3 1D chains in 3 are further linked by bridging SCN⁻ ligands to afford a three-dimensional (3D) framework. Complex 2 possesses a (6,3) two-dimensional (2D) layer structure. In 1-4, the hydrogen bonds involving the amide groups play important role to stabilize the resultant frameworks. The photoluminescence properties of the DPBA-3 and the complexes were studied in the solid state at room temperature.     

Anion-directed assembly of metal-organic coordination complexes from 1,3-imidazolidine-2-thione ligand and silver salts

Five novel silver (Ι) complexes with 1,3-imidazolidine-2-thione ligand formulated as [Ag₂(η¹-SC₃H₆N₂)₆]SO₄ (1), [Ag₂(μ₂-SC₃H₆N₂)₂(η¹-SC₃H₆N₂)₄](NO₃)₂ (2), [Ag(μ₂-SC₃H₆N₂)Br]_n (3), [Ag₂(μ₂-SC₃H₆N₂)₃(CH₃COO)₂]_n (4), [Ag(μ₂-SC₃H₆N₂)Cl]_n (5) have been synthesized under similar conditions except for different anions and solvents. They are structurally characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. Complex 1 is a binuclear complex, with SO₄²⁻ anions as the counteranions. Complex 2 is a molecular binuclear silver cluster, with NO₃⁻ anions as the counteranions. Complex 3 shows a novel 2D lamella structure constructed by the S atom of 1,3-imidazolidine-2-thione ligand and Br⁻ anions, and exhibits 12-membered metallacyclic rings in its structure. Complex 4 is a novel 2D layered polymer with a graphite-like array of silver (I) ions, with CH₃COO⁻ anion coordinated to silver(I) ions by O atom. Complex 5 shows a 3D diamond-like network structure constructed by the sulfur atom of 1,3-imidazolidine-2-thione ligand and Cl⁻ anions.     

Self-assembly of three novel mixed-ligand coordination polymers: Formation of 2-D grids, 1-D chains and ladders and crystal band structure

Hydrothermal reaction of the carboxylate-based ligands with metal salts (or oxide) and 4,4′-bipyridine as a second linker, afforded three new coordination polymers, namely, [Co(PCPA)₂(4,4′-bpy)]_n (1) with 2-D rectangle grids, Cu(PCPA)₂(4,4′-bpy)]_n (2) with a linear chain, [Ag(PCPA)(PCPAH)(4,4′-bpy) · H₂O]_n (3) with 1-D molecular ladder (4,4′-bpy = 4,4′-bipyridine; PCPA = p-chlorophenoxyacetate; PCPAH = p-chlorophenoxyacetic acid). It is noticeable that compound 3 is also a supramolecular framework built by coordination bonds, weak interactions between Ag ions, π-π stacking interactions and hydrogen-bonded interactions. The three compounds with different structure motifs have been characterized by elemental analyses, IR spectra, ultraviolet-visible diffuse reflection integral spectra, fluorescent spectra and single crystal X-ray diffraction analysis. Furthermore, the bonding properties of compound 3 were investigated in terms of the absorption spectrum, as well as the calculated band structures and density of states.     

Two novel three-dimensional coordination polymers based on metal clusters: Hydrothermal syntheses, crystal structures and luminescence

Two novel coordination polymers with interesting supramolecular architecture, [Zn₂(OH)(BTC)(bix)] (1) and [Cd₂(CDC)₂(bix)₂] (2) (H₃BTC = 1,3,5-benzenetricarboxylic acid, H₂CDC = trans-1,4-cyclohexanedicarboxylic acid and bix = 1,2-bis(imidazol-1-ylmethyl)benzene) have been obtained via hydrothermal reaction and characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 features a 3D network with one of the scarce (3,8)-connected (4³)₂(4⁶.6¹⁸.8⁴) topology based on the rare CdI₂-type layer constructed from secondary building units (SBUs) of zinc clusters. While 2 exhibits a scarcely reported eight-connected 3⁶.4¹⁶.5⁶ net with dinuclear cadmium clusters as secondary building units. The luminescent properties of 1 and 2 along with the bix ligand in the solid state were investigated.     

A blue fluorescent Cd(II) coordination polymer with 3,5-diaminobenzoic acid ligand: synthesis, crystal structure and fluorescent property

Under hydrothermal conditions, the reaction of 3,5-diaminobenzoic acid (HDABC) with Cd(ClO₄)₂ ∼ 6H₂O affords a novel 2D network, {[Cd(DABC)₂][Cd(DABC)₂(H₂O)₂]}_n (1), which, represents the first example of 2D neutral polymeric material containing DABC ligand with strong blue fluorescent emission in the solid state.     

Hydrothermal synthesis, crystal structure and magnetic characterization of two 4f-3d heterometallic coordination polymers

Two new 4f-3d heterometallic coordination polymers [Gd₂Co(L₁)₃(ox)(H₂O)₄]·2.5H₂O (1, L₁ = pyridine-2,5-dicarboxylate anion, ox = oxalate dianion) and [GdNi(L₂)₂(ox)_0.5(H₂O)₃]·3H₂O (2, L₂ = pyridine-2,3-dicarboxylate anion) were successfully synthesized under hydrothermal conditions. In compound 1, one dimensional heterometallic and lanthanide infinite sheets were constructed with sole L₁ spacers and L₁-ox mixed bridges, respectively. While similar one dimensional heterometallic infinite sheet and normal lanthanide infinite zigzag chain were formed based on sole L₂ and L₂-ox mixed bridges, respectively in compound 2. Both of the two compounds exhibited new and interesting three dimensional topologies. In addition, the magnetic properties of the two compounds were analyzed via solid-state dc magnetic susceptibility measurements.     

Metal-dependent dimensionality in coordination polymers of a semi-rigid dicarboxylate ligand with additional amide groups: Syntheses, structures and luminescent properties

Three new coordination polymers, [CdL(H₂O)₃·H₂O]_n (1), [MnL(H₂O)₂]_n (2) and [ZnL]_n (3) (L = 2,2′-[1,4-bis(-benzamido)]diacetate) have been hydrothermally synthesized. Complex 1 and complex 2 are 1-D infinite zigzag chain and 2-D rectangular grid networks, respectively, in which are further stabilized by hydrogen bonds, thus affording two 3-D supramolecular frameworks. Complex 3 exhibits a (4, 4)-connected PtS topology. Moreover, an unusual phenomenon has been observed that the dimension of these coordination polymers gradually increases with the decrease of coordination numbers of metal ions. In addition, complex 1 exhibits a strong blue luminescence in the solid state at room temperature and may be potential candidate for luminescent materials.     

A copper(II) coordination polymer with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges

A new one-dimensional (1D) copper(II) complex, [Cu₂(dpk · CH₂O)(N₃)₃]_n (dpk · CH₂OH = unimethylated diol of di-2-pyridyl ketone) (1), has been synthesized and characterized. X-ray crystal structure study reveals that 1 is composed of 1D copper(II) chain with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges. The magnetic determination indicates that ferromagnetic interaction dominates in this new 1D S = 1/2 system.     

Ultramicroporous channel lanthanide coordination polymers of 2,5-pyrazinedicarboxylate

Five lanthanide coordination polymers with composition {[Ln(pzdc)_1.5(H₂O)₃] · 0.5H₂O}_∞, (Ln = Pr, 1; Nd, 2; Sm, 3; Eu, 4; Gd, 5; pzdc = 2,5-pyrazinedicarboxylate), have been synthesized by reacting Ln(NO₃)₃ · 6H₂O with 2,5-pyrazinedicarboxylic acid under hydrothermal condition in the absence of additional base and characterized by elemental analysis, IR spectra and TG analysis, as well as single-crystal X-ray diffraction. They crystallize isostructurally in the triclinic space group P-1 and the cell parameters agree with the ionic radii of the Ln(III) ions. Each trivalent rare earth ion is nine coordinate in an N₂O₇ environment. The ligand 2,5-pyrazinedicarboxylate adopts three coordination modes, through which the lanthanide ions are linked together to form an infinite three dimensional structure. A 1D channel exists along the (1 0 0) direction which accommodates uncoordinated water by hydrogen bonds. Heating of 4 at 120 °C evacuated the uncoordinated water while retaining its single crystallinity with only minor change in cell parameters (crystal 6, [Eu(pzdc)_1.5(H₂O)₃]_∞). This hydrophilic ultramicroporous channel is selective to accommodate water only among common solvents, which has some potential interest for solvent separation.