Architecture of zero-, one-, two- and three-dimensional structures based on metal ions and pyrazine-2,6-dicarboxylic acid

Six new complexes: [Ln₂(pzda)₃(H₂O)₂] · 2.5H₂O (Ln = Nd, (1); Eu, (2)), [Co(pzda) (bpe)] · 0.125(bpe) · 1.75H₂O (3), [Mn(pzda)(H₂O)_1.5] (4), [Co₂(pzda)₂(bpe)(H₂O)₄] · 0.5(CH₃OH) · H₂O (5) and [Co(pzda)(2,2′-bpy)(H₂O)] · 0.5H₂O (6) (H₂pzda = pyrazine-2,6-dicarboxylic acid, bpe = 1,2-bis(4-pyridyl)ethane, 2,2′-bpy = 2,2′-bipyridine) were obtained from metal salts and H₂pzda under hydro(solvo)thermal conditions. The single crystal X-ray structural analysis reveals that the title complexes have different structures, ranging from zero- to three- dimensions, which are mainly due to the different metal ions, and especially the coordination modes of the pzda ligands. Complexes 1 and 2 have 3D metal-organic frameworks containing a 1D tri-strand array, in which the pzda ligand adopts a pentadentate mode to link lanthanide ions. Complex 3 has a 2D metal-organic framework, in which the pzda ligand acts in a tetradentate mode to connect Co(II) ions into 1D chains, which are further connected by bpe spacers into a 2D framework. While in 4, both of the two carboxylate groups of the pzda ligand adopt μ₂-O bridging modes to link Mn(II) ions into a 1D coordination polymer, which is further assembled into a 2D supramolecular network containing double-stranded hydrogen-bonded helical chains. In both 5 and 6, the pzda ligand binds metal ions as a tridentate ligand (ONO mode) to form zero dimensional structures. Complex 5 is a binuclear molecule, while 6 is a mononuclear complex, which can be attributed to the bridging ligand bpe for 5 and the terminal auxiliary ligand 2,2′-bpy for 6.     

One-dimensional coordination polymers of praseodymium(III)–vanadium(V) complexes with pyridine-2,6-dicarboxylic acid

This paper represents the hydrothermal synthesis of new isomorphous lanthanide–vanadium complexes with one-dimensional coordination polymers: [Pr₂(VO₂)₂(dipic)₄(H₂O)₉] · nH₂O with dipic = pyridine-2,6-dicarboxylic acid and n = 7.75. The structure determination shows a unique one-dimensional structure in which three types of chains run along the c-axis: the chain of positively charged praseodymium complexes bridged by a dipic ligand ([Pr(dipic)(H₂O)₅]⁺), the chain of negatively charged, stacked vanadium complexes ([VO₂(dipic)]⁻), and the chain of neutral praseodymium complexes with a bridged dipic ligand and a coordinating dipic ligand ([Pr(dipic)[VO₂(dipic)](H₂O)₄]). Such one-dimensional chains provide open channels which can accommodate water molecules. Not only accommodated water molecules but also ones coordinated to praseodymium ions were easily removed and absorbed upon heating at 200 °C and exposure of humidity at room temperature, respectively.     

Synthesis,structure and thermochemical study of a cobalt energetic coordination compound incorporating 3,5-diamino-1,2,4-triazole and pyridine-2,6-dicarboxylic acid

An energetic coordination compound [Co₂(C₂H₅N₅)₂(C₇H₃NO₄)₂(H₂O)₂]·2H₂O (Hdatrz(C₂H₅N₅) = 3,5-diamino-1,2,4-triazole, H₂pda(C₇H₅NO₄) = pyridine-2,6-dicarboxylic acid) has been synthesized and characterized by elemental analysis, chemical analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analysis confirmed that the compound possessed a di-nuclear unit and featured a 3D super-molecular structure. Furthermore, a reasonable thermochemical cycle was designed based on the preparation reaction of the compound and the standard molar enthalpy of dissolution of reactants and products was measured by the RD496-2000 calorimeter. Finally, the standard molar enthalpy of formation of the compound was determined to be −(2475.0 ± 3.1) kJ · mol⁻¹ in accordance with Hess’s law. In addition, the specific heat capacity of the compound at T = 298.15 K was determined to be (1.13 ± 0.02) J · K⁻¹ · g⁻¹ by RD496-2000 calorimeter.     

Syntheses, structures, and magnetic properties of new rare earth coordination polymers constructed by 1,3,5-benzenetriacetic acid

Three new coordination polymers with formula [Gd(bta)(H₂O)·1.39H₂O] _n (1), [Dy(bta)(H₂O)·1.35H₂O] _n (2) and [Y(bta)(H₂O)₂·0.5H₂O] _n (3) were synthesized by using corresponding rare earth nitrates and 1,3,5-benzenetriacetic acid (H₃bta) under hydrothermal/solvothermal reaction conditions, and characterized by single-crystal X-ray diffraction. In these complexes, the carboxylate groups of bta³⁻ adopt different coordination modes, namely one carboxylate group adopts μ₂-η¹:η¹-bridging and each of the other two carboxylate groups adopts μ₂-η²:η¹-bridging coordination modes in 1 and 2, and one carboxylate group adopts a μ₂-η²:η¹-bridging coordination mode and each of the other two carboxylate groups adopts a μ₂-η¹:η¹-bridging mode for the major component and one carboxylate group adopts a μ₂-η²:η¹-bridging coordination mode, one has a μ₂-η¹:η¹-bridging mode and the third has a monodentate mode for the minor component in 3. The magnetic properties of the complexes 1 and 2 were investigated in the temperature range of 1.8–300 K.     

Syntheses,crystal structures,and luminescence of carboxylato-bridged coordination compounds

Two 2-D metal carboxylate coordination compounds [Tb(pydc)(ox)_1/2(H₂O)₂] (1) and [Cd(pydc)(me)(H₂O)]₂ · H₂O (2) (pyridine-2,5-dicarboxylic acid = pydc, oxalic acid = ox, me = methanol) have been synthesized under hydrothermal conditions. Carboxylates are building blocks in the formation of zigzag chain and cockle stair-like chain structures for 1 and 2, respectively. Both the compounds have been structurally determined by single-crystal X-ray diffraction, and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and fluorescence spectra.     

Synthesis and crystal structures of two new zigzag versus helical coordination polymers based on diphenic acid

Two new coordination polymers, [Mn(dpa)(2,2′-bipy)] _n (1) and [Ni(dpa)(2,2′-bipy)] _n (2) (H₂dpa = 3,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = bipyridine), have been synthesized and structurally characterized by elemental analysis, IR, and X-ray diffraction. Single-crystal X-ray analyses revealed that 3,4′-diphenic acid acts as a bridging ligand, exhibiting rich coordination modes to link metal ions: μ ₂–η ¹: η ¹, μ ₁–η ¹: η ¹, and μ ₁ –η ¹: η ⁰. Compound 1 demonstrates a 1-D zigzag chain. Compound 2 is a 1-D helical chain. In 1 and 2, there exist intermolecular π–π stacking interactions and non-covalent interactions responsible for the stabilization of the supramolecular structure. In 1, the Mn(II) chains exhibit a weak antiferromagnetic interaction.     

Solid and solution states studies of two Mn(II) complexes based on N-oxidized pyridine-2,5-dicarboxylic acid

Abstract

Two coordination complexes, [Mn₂(pydco)₂(phen)₂(H₂O)₂]·2H₂O (1) and [Mn(3-pyco)₂(H₂O)₄] (2), based on Mn(II), pyridine-2,5-dicarboxylic acid N-oxide (H₂pydco), and 1,10-phenanthroline (phen) as organic ligands have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X-ray diffraction. We have synthesized the first Mn(II) complex of H₂pydco. Interestingly, in situ hydrothermal decarboxylation occurred in 2 and (pydco)^2– was totally transformed into pyridine-3-carboxylate N-oxide (3-pyco)^– under hydrothermal conditions. The complexation reactions of these molecules with Mn²⁺ ions were investigated by means of solution studies. The stoichiometry of the most abundant species in the solution (prior to the pH at which precipitation occurs) was very close to that of the corresponding crystalline solid-state complexes.     

Hydrothermal synthesis,structural investigation,and magnetic properties of 2-D layered lanthanide (Ln = Pr,Eu, Gd,Tb, and Er) coordination polymers possessing infinite 1-D nanosized cavities

Five 2-D Ln(III) coordination polymers, [Ln(PDA)(PDAH)]_n (PDA = 2,6-pyridinedicarboxylate), have been obtained under mild hydrothermal condition. In each coordination polymer, PDA is tetradentate and pentadentate, while lanthanides have coordination number eight to generate trigonal prismatic, triangular face bicapped LnO₆N₂ geometry having 9 triangular and 2 square faces. Two different types of bridging oxygens are responsible to grow the 2-D coordination polymers providing open channels possessing infinite 1-D nanosized cavities. Adjacent 2-D chains are further extended to a 3-D hydrogen-bonded layered network through intermolecular π–π interactions and C–H?O hydrogen bonds. Four lanthanides are arranged roughly at the vertices of a square and bridged by eight carboxylates leading to the overall tetrahedral shape of the secondary building units. The abnormal behavior of lanthanide contraction for the atomic radii of europium can be attributed to overlapping of electron clouds. The overall magnetic behavior is typical for the presence of antiferromagnetic exchange coupling interactions. Thermal decomposition analysis reveals that the coordination polymers have significant thermal stability. The coordination polymers are further characterized using elemental analysis and FT-IR spectroscopy.     

Synthesis,crystal structure and magnetic properties of 2D bi-layered coordination polymer

A new coordination polymer, [Ni(pydc)(H₂O)₂]?·?H₂O (1) (H₂pydc?=?pyridine-3,4-dicarboxylic acid), have been synthesized by treating Ni(II) nitrate with 3,4-pyridinedicarboxylic acid under hydrothermal conditions. The single-crystal X-ray structure reveals that 1 is a 2D bi-layered coordination polymer. Single-crystals are triclinic, space group P 1 , with a?=?7.065(3), b?=?7.812(4), c?=?9.031(4)?Å, α?=?75.568(8), β?=?68.970(8), γ?=?75.927(8)°, V?=?444.0(3)?ų, Z?=?2. Variable temperature magnetic susceptibility measurements demonstrate a ferromagnetic interaction in 1.     

Synthesis,characterization and crystal structure of a novel three-dimensional supramolecular architecture formed by manganese(II) and pyridine-2,5-dicarboxylic acid

A novel three-dimensional supramolecular compound formed by Mn(II) and pyridine-2,5-dicarboxylic acid of formula [Mn(Pydc)₂(H₂O)₂] (Pydc?=?pyridine-2,5-dicarboxylic acid) has been synthesized and characterized by elemental analyses, IR, electronic spectra, thermogravimetric analysis and X-ray diffraction techniques. The X-ray structure shows that the central Mn(II) ion is coordinated by two water molecules and two chelated Pydc ligands. Water molecules coordinate with Mn(II) ions in the cis mode. Intermolecular hydrogen bonds play an important role in stabilization of the lattice and construction of the supramolecular network.     

Syntheses and characterizations of four metal coordination polymers constructed by the pyridine-3,5-dicarboxylate ligand

A series of metal-organic frameworks, namely [Ni(PDB)(H₂O)]_n (1), [Pb(PDB)(H₂O)] · (H₂O) (2), [Co₂(PDB)₂(bpy)₂(H₂O)₄] · 4H₂O (3) and [Co₂(PDB)₂(phen)₂]_n (4) (H₂PDB = pyridine-3,5-dicarboxylic acid, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized based on pyridine-3,5-dicarboxylate acid and two neutral chelate ligands, with different metal ions such as Ni^II, Co^II and Pb^II, under hydrothermal conditions. The framework structures of these polymeric complexes have been determined by the X-ray single crystal diffraction technique. In the four complexes, the pyridine-3,5-dicarboxylate acid ligand exhibits diverse coordination modes, which play an important role in the construction of metal-organic frameworks. The thermal analyses of these four complexes have been measured and discussed. In addition, complex 2 shows strong phosphorescent emission at room temperature and the magnetic measurement of the polymer of 4 reveals a typical antiferromagnetic exchange.     

Structures and magnetic properties of several novel lanthanide coordination polymers based on thiophene-2,5-dicarboxylic acid

Eight novel lanthanide complexes: {Ln(TDA)1.5(H2O)2}n (Ln = Pr(1a), Nd(2a)) and {Ln(TDA)(Ac)(H2O)}n (Ln = Pr(1), Nd(2), Eu(3), Gd(4), Tb(5), Dy(6); TDA = Thiophene-2,5-dicarboxylic acid anion) have been constructed by hydrothermal reaction. Structural analyses reveal that complexes 1a and 2a belong to the space group C2/c, exhibiting three-dimensional (3D) frameworks. Complexes 1-6 with P21/c space group were prepared in the presence of excessive ammonium acetate, giving rise to interesting 3D frameworks different from those of 1a and 2a. Magnetic property studies of 4-6 reveal the weak antiferromagnetic interaction exists between adjacent Gd3+ in 4. The complex 6 displays rather rare slow magnetization relaxation behavior in 3D frameworks.     

Synthesis and structures of two novel non-centrosymmetric metal-organic polymers containing 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid ligands

Two novel non-centrosymmetric coordination polymer, [Zn₂(PIDC)(H₂O)Cl]_n (1) and {[Mn(HPIDC)H₂O]·2H₂O}_n (2) have been synthesized through hydrothermal method and characterized by IR, elemental analysis and single-crystal X-ray diffraction. Complex 1 crystallized in a chiral space group P2₁2₁2₁ has a 2D network structure. Complex 2 is a 3D open framework with 1D channel where 1D zigzag water chains are reside through hydrogen-bonding interactions and crystallized in a chiral space group C_c. Both 1 and 2 display a strong second harmonic generation (SHG) response.     

Copper(II) complexes with pyridine-2,6-dicarboxylic acid from the oxidation of copper(I) iodide

Via an oxidation reaction of Cu(I) iodide with pyridine-2,6-dicarboxylic acid (H₂L) in DMF three copper(II) complexes, [(CH₃)₂NH₂]₂[CuL₂] (1), K₂[CuL₂]?H₂L?H₂O (2) and [Cu(L)(H₂O)]_n (3), were synthesized and characterized. The structures of 1–3 were determined by single crystal X-ray diffraction studies. In-situ DMF decomposition produces dimethylamine base under solvothermal conditions and a proton transfer reaction takes place for the complex formation of 1. 3-D networks are stabilized in 1 and 2 via hydrogen bonds. Complex 3 is a 1-D coordination polymer with Cu-O semi-coordination bonds. Thermal decomposition of the complexes results in the corresponding metal oxides. Also, the electrochemical behavior of 1 was determined to be a metal-centered and diffusion-controlled, one-electron reduction process.     

2-D coordination polymers of copper and cobalt with 3,4-pyridinedicarboxylic acid: synthesis,characterization, and crystal structures

Two new complexes involving 3,4-pyridinedicarboxylic acid (3,4-H₂pdc), copper(II) and cobalt(II) complexes, {[Cu(3,4-Hpdc)₂(H₂O)₂]·2dmso}_n (1) and {[Co(3,4-Hpdc)₂(H₂O)₂]·2H₂O·2dmso}_n (2) (dmso = dimethylsulfoxide), have been synthesized by the diffusion method and characterized by elemental analysis, IR spectroscopy, thermal analysis, powder and single-crystal X-ray diffraction analysis, and electron paramagnetic resonance (EPR). In both compounds, the metal coordination sphere is composed of a trans-MO₄N₂ core and adopts a distorted octahedral geometry in accordance with X-ray diffraction and EPR results. 3,4-Hpdc^? ligands bridge the metal centers giving two-dimensional (2-D) coordination polymers with four-connected uninodal nets of (4,4) topology.     

Two novel 3-D coordination polymers based on isonicotinic acid: Syntheses, crystal structures and fluorescence

The hydrothermal reactions of isonicotinic acid (HIso) and metal salts yielded two novel 3-D coordination polymers {[Cu₄(Iso)₄(μ₃-O)₂(C₂H₅OH)₂]·2C₂H₅OH·C₂H₆N₄}_n (1), {[Cd(Iso)₂(H₂O)]·OHCCHO}_n (2), in which 1 was constructed from 32-membered rings and 3-D interpenetrating network of 2 from 42-membered rings. The fluorescent characterizations show the emissions at 565 nm for 1 and 440 nm for 2 possibly assigned to LMCT and IL, respectively.     

Crystal growth,characterization and photoluminescence study of a novel one dimensional coordination polymer of Cd(II) with thiophene-2,5-dicarboxylic acid

A novel one dimensional coordination polymer of Cd(II) with thiophene-2,5-dicarboxylic acid (H₂tdc), {[Cd(tdc) (H₂O)₃]·1.5H₂O}_n has been prepared by gel diffusion method. Elemental analysis, single crystal and powder X-ray diffraction studies, FT-IR and UV–visible spectral studies were used to characterize the title compound. Cd-thiophene units form a linear chain in the crystal structure. Thiophene rings of a linear chain are stacked parallel to each other while the thiophene rings of the adjacent chains are intercalated and stacked ant-parallel to each other. Extensive hydrogen bond formation and π-π interactions between thiophene moieties are responsible for the supramolecular architecture. TG/DTG studies confirm the presence of both lattice and coordinated water molecules. Photoluminescence studies showed that the title compound is red shifted by 46 nm compared to ligand.     

A series of novel metal-ferrocenedicarboxylate coordination polymers: crystal structures, magnetic and luminescence properties

Novel two-dimensional layered lanthanide(III)-ferrocenedicarboxylate coordination polymers {[M(η²-O₂CFcCO₂-η²)(μ₂-η²-O₂CFcCO₂-η²-μ₂)_0.5(H₂O)₂]·mH₂O}_n (Fc=(η⁵-C₅H₄)Fe(η⁵-C₅H₄), M=Tb³⁺, m=2, 1; M=Eu³⁺, m=2, 2; M=Y³⁺, m=1, 3) with trapezium-shaped units and one-dimensional wave-shaped Cd(II)-ferrocenedicarboxylate polymer {[Cd(η²-O₂CFcCO₂-η²)(H₂O)₃]·4H₂O}_n (4) have been prepared and structurally characterized by single crystal diffraction. In polymers 1-3, each central metal ion (Tb(III), or Eu(III) or Y(III)) is located in a pseudo-capped-tetragonal prism coordination geometry, and ferrocenedicarboxylate anion ligands have two coordination modes (bidentate-chelating mode and tridentate-bridging mode). The magnetic behaviors for 1 and 2 are studied in the temperature range of 5.0-300 K. The results show that the paramagnetic behavior of 2 is mainly due to the effective spin-orbital coupling between the ground and excited states through the Zeeman perturbation, and the weak magnetic interaction between Eu³⁺ centers can be observed. In addition, compared with sodium ferrocenedicarboxylate, the fluorescent intensities of the polymers 1-4 are enhanced in the solid state.     

Two lead coordination polymers with nitrilotriacetic acid and oxydiacetic acid: synthesis,characterization, and crystal structure

Two lead coordination compounds [Pb₂(nta)]NO₃ (1) and [Pb(oda)] (2) have been synthesized by slow evaporation or hydrothermal conditions using nitrilotriacetic acid (nta) and 2,2′-oxydiacetic acid (oda) as ligands, respectively. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction, infrared absorption spectrum, and thermogravimetric analysis. Compound 1 is a 2-D honeycomb-like layer structure with (6,3) topology. When the bonding limit of Pb–O extends from 2.76 to 2.90 Å, potential weak Pb–O bonds can be found in 1, and the 2-D layer structure can be further linked to generate a 3-D 4-connected supramolecular sra net with the (4².6³.8) Schläfli symbol. Compound 2 contains a 1-D infinite Pb–O chain which is connected through µ₃-, µ₄-, and µ₅-coordination modes of oda to form a new 3-D structure.