Metal Carboxylate Chains Research Articles

Lanthanide metal-organic frameworks containing ferromagnetically coupled metal-carboxylate chains showing slow magnetic relaxation behavior

Lanthanide metal-organic frameworks (Ln-MOFs) with slow magnetic relaxation behavior are of great interest to scientists due to their rich and peculiar physical phenomena and spin-related applications. In this contribution, the syntheses, characterizations and magnetic properties of two new Ln-MOFs: {[Ln2(btpdc)3·DMF·2H2O]·2DMF·4H2O}n (Ln = Dy (1), Gd (2), H2btpdc = benzo[b]thiophene-2,6-dicarboxylic acid) are reported. Single crystal X-ray diffraction experiments show the two complexes are isostructural with three dimensional (3D) porous framework structure constructed by metal-carboxylate chains separated by long organic linkers. Direct-current (dc) magnetic susceptibilities recorded under 1000 Oe reveal the overall exchange couplings in both the two MOFs are ferromagnetic. Interestingly, the ferromagnetic coupled metal-carboxylate chains in 1 are sufficiently isolated by the long organic linkers that makes 1 exhibit slow magnetic relaxation behavior and Ising-like behavior which was rarely reported for lanthanide-carboxylate complexes.

Two new 3D lanthanide-organic frameworks based on rod-shaped metal-carboxylate chain SBU: Synthesis, characterization and luminescent detection of Fe3+ and S2− in aqueous solution

The study of metal-organic frameworks (MOFs) as luminescence sensors for the detection of polluting molecules and ions are of great importance to the health of all creatures in the world. In this research field, lanthanide ions, especially for Eu3+ and Tb3+, have intrinsic advantages based on their outstanding luminescent properties. To develop smart luminescence sensors towards heavy metal ions and acid anions, two new lanthanide(III)-based MOFs: {[Ln2(btpdc)3·DMF·2H2O]·2DMF·4H2O}n (Ln ​= ​Eu (1), Tb (2), H2btpdc ​= ​benzo[b]thiophene-2,6-dicarboxylic acid) were designed and synthesized under solvothermal condition based on a dicarboxylate ligand H2btpdc. Single crystal X-ray diffraction tests show the two complexes are isostructural with three dimensional (3D) porous framework structure. Notably, both of them exhibit good chemical stability in water. Under the excitation of ultra-violet light, 1 can exhibit strong Eu3+-based red light emission in both solid state and aqueous suspension while 2 doesn't show observable luminescence emission. The luminescence sensing experiments performed on 1 reveal that it can be employed as a smart “turn-off” luminescence sensor for the detection of Fe3+ or S2− in aqueous solution with high selectivity, low detection limit, good anti-interference ability and recyclability. The obtained quenching constant Ksv and detection limits are 2.316 ​× ​104 ​M−1 and 0.26 ​μM, respectively, for Fe3+, and 1.38 ​× ​104 ​M−1 and 1.05 ​μM, respectively, for S2−.

A helix-based cobalt(II) coordination polymer with mixed ligands of homophthalic acid and 2,5-Bis(4′-pyridyl)-1,3,4-oxadiazole: synthesis, structure and magnetic property

A novel Cobalt(II) coordination polymer formulated as [Co(hmph)(4-bpo)(H2O)]n (1) was obtained through hydrothermal method, and then characterized by single-crystal X-ray diffraction, elemental analysis and powder X-ray diffraction (H2hmph = homophthalic acid, 4-bpo = 2,5-bis(4′-pyridyl)-1,3,4-oxadiazole). Complex 1 displays a three-dimensional architecture based on interweaving helix chains, which can be defined as a 4-connected uoc network with the Schläfli symbol of (42.84). TGA experiment reveals that complex 1 can maintain its integrity until 214 °C. Furthermore, the magnetic data indicate there is weak antiferromagnetic interaction between the neighbor Co(II) atoms in the metal-carboxylate chain.

A dual fluorescent sensor coordination polymer for efficient recognition of acetylacetone and Cr(VI) anions

A novel Cu(II) coordination polymer (compound 1) formulated as [Cu(HL)(bpy)]·H2O (H3L = 4-(2′,3′-Dicarboxylphenoxy) benzoic acid, bpy = 2,2′-bipyridine) has been successfully prepared via solvothermal methods and characterized by structural analyses. Crystallographic research reveals that compound 1 exhibits a 1D metal-carboxylate chain, which self-assembles into a final 3D supramolecular network through the interchain hydrogen bonds. Further investigation indicates that compound 1 possesses excellent chemical stability. It maintains good stability in various solvents and aqueous solution with pH range of 2–11 for two weeks. The luminescence investigations manifest that compound 1 can be used as a multi-responsive fluorescence sensor for sensing acetylacetone (Hacac), CrO42− and Cr2O72− with high selectivity, sensitivity and excellent anti-interference ability through luminescence quenching. Furthermore, the probable mechanisms of selective detection have been explored in detail.

Eu(III)-organic framework as a multi-responsive photoluminescence sensor for efficient detection of 1-naphthol, Fe3+ and MnO4− in water

A new three-dimensional Eu(III) metal–organic framework Eu(III)-MOF-1 formulated as [Eu3(BDC)4.5(H2O)(DMF)2] (H2BDC = 1,4-benzenedicarboxylic acid), has been successfully synthesized by solvothermal methods and characterized by structural analyses and luminescence studies. Crystallographic studies reveal that the Eu-MOF-1 exhibits an unusual 3D framework based on 1D metal-carboxylate chains. Significantly, the luminescence explorations demonstrate that the Eu-MOF-1 is the first multi-responsive fluorescence sensor for sensing biomarker 1-naphthol (1-N) of carbaryl exposure, Fe3+ ions and MnO4− ions with high sensitivity, selectivity and excellent recyclability through luminescence quenching. Moreover, the possible mechanisms of selective detection have been investigated in detail. This material could be a promising luminescent sensor for practical applications.

Ionic liquid templated novel porous anionic cobalt(II) coordination framework based on rod-shaped metal-carboxylate chains

A novel porous anionic cobalt(II) coordination framework based on rod-shaped metal-carboxylate chains, [BMI][Co3(L)2(HCOO)(H2O)2] (1) (H3L = 3,4-bi(4-carboxyphenyl)-benzoic acid, [BMI]Br = 1-butyl-3-methylimidazolium bromide), has been prepared under the combination of solvothermal and ionothermal syntheses. [BMI]Br ionic liquid play a structure directing role and [BMI]+ cation is occluded into the ultimate structure. Complex 1 possesses 1D channels (11.4 × 13.6 Å) constructed by 1D cobalt(II)-carboxylate secondary building unit (SBU) and H3L ligands. The study suggests that [BMI]Br, the kind of molecular solvents as well as the anion of the cobalt(II) salts all play key roles in the formation of the title anionic framework.

Five 3D lanthanide-based coordination polymers with 3,3,6T13 topology: Structures and luminescent sensor for Hg2+ and Pb2+ ions

A series of isostructural lanthanide coordination polymers Ln-CPs, {[Ln2(PBA)3(H2O)3]·DMF·3H2O}n(Ln = La 1, Nd 2, Sm 3, Eu 4, Dy 5), based on a tripodal nitrogen-containing carboxylic ligand (H2PBA=5-(4-pyridin-3-yl-benzoylamino)-isophthalic acid), have been successfully synthesized under solvothermal conditions. Structural analyses show that compounds 1–5 are isomorphous and crystallize in triclinic space group Pī, and feature an interesting 3,3,6T13 network topology with point symbol (4·52)2(42.52.10·6·72)(58.64.10·6·72). There exist two kinds of 1D metal-carboxylate chains, which are further extended into 3D framework through the connection of PBA2- ligands. Moreover, luminescent spectra of compound 4 are also investigated in visible region, which indicates that it could be used to detect toxic metal cations with relatively high sensitivity and selectivity towards Hg2+ and Pb2+ in DMF solvent.

Syntheses, structures and magnetic properties of three cobalt(II) coordination polymers based on flexible itaconic acid ligands

Three Co(II) coordination polymers, namely [Co(ia)(bpe)0.5(H2O)]n (1), {[Co(ia)(bib)(H2O)]·H2O}n (2) and {[Co(ia)(btmb)(H2O)]·H2O}n (3) (H2ia = itaconic acid, bpe = 1,2-bi(4-pyridyl)ethene, bib = 1,4-bis(1-imidazoly)benzene, btmb = 4,4′-bis(triazol-1-ylmethyl)biphenyl), were synthesized solvothermally and analyzed by single-crystal X-ray diffraction and elemental analysis. Complex 1 is a three-dimensional metal–organic framework with ins topology type and Schlafli symbol (63)(65·8). The alternate arrangement of left- and right-hand 21 helix metal–carboxylate chains affords an overall achiral structure. Complex 2 consists of a 3D metal–organic framework with ia2− anions and bib ligands as linkers with (42·84) lvt topology. Complex 3 displays a 2D layer structure, with a three-dimensional supramolecular structure produced from the parallel stacking layers by abundant interlayer hydrogen bonds. Complexes 1 and 2 both obey the Curie–Weiss law within a certain temperature range and exhibit antiferromagnetic coupling between the Co(II) centers across the carboxyl groups of the dianionic ia2− ligands.

Syntheses, structures and magnetic properties of nine coordination polymers based on terphenyl-tetracarboxylic acid ligands.

Nine coordination polymers (CPs) [Mn(H3L)(H2L)0.5(phen)]n (1), [Ni2L(phen)2(μ2-H2O)]n (2), {[Mn2L(phen)2]·(DMA)(H2O)}n (3), {[Co2L(μ2-H2O)(μ2-DMA)]·DMF}n (4), [CoL0.5(H2O)(phen)]n (5), {[Ni2L(μ2-H2O)(μ2-DMA)]·DMA}n (6), {[Co2L(μ2-H2O)(μ2-DMA)]·DMA}n (7), {[Ni2L(μ2-H2O)(H2O)2(DMF)2]·(H2O)2(DMF)}n (8), and {[Ni4L2(μ2-H2O)4(H2O)2]·(H2O)2(NMP)}n (9) (H4L = 1,1':4',1''-terphenyl-2',4,4'',5'-tetracarboxylic acid, DMA = N,N-dimethylacetamine, DMF = N,N-dimethylformamide, NMP = N-methyl-2-pyrrolidone, phen = 1,10-phenanthroline) have been synthesized and structurally characterized. Crystal structural analyses reveal that 1 features the uninodal 2D (4,4) network with the dinuclear Mn2(COO)2 units as 4-connected nodes. 3 and 5 possess the binodal 2D (4,4) network with dinuclear Mn2(COO)4/Co2O2 units and L4- ligands as 4-connected nodes, respectively. In 2 and 8, each dinuclear Ni2(COO)2(μ2-H2O) unit links to four L4- ligands and each L4- ligand bridges four dinuclear Ni2(COO)2(μ2-H2O) units to generate the 3D framework, which can also be rationalized as a binodal 4,4-connected (42·84)(42·84) topological network by considering the dinuclear Ni2(COO)2(μ2-H2O) units as non-planar 4-connected nodes and L4- ligands as planar 4-connected nodes, respectively. In 4, 6-7 and 9, there exist a series of parallel-aligned metal-carboxylate chains, which are linked along two directions by para-terphenyl moieties of L4- ligands to generate the 3D frameworks. Moreover, direct current magnetic susceptibility measurements were carried out to study their magnetic properties. In complexes 2 and 9, weak ferromagnetic interactions between the magnetic centers were observed. In addition, the other compounds show weak antiferromagnetic exchange interactions between the adjacent metal ions.

Flexible Porous Coordination Polymers from Divergent Photoluminescent 4-Oxo-1,8-naphthalimide Ligands.

Two new luminescent ditopic naphthalimide-derived ligands, N-(4-cyanophenylmethylene)-4-(4-cyanophenoxy)-1,8-naphthalimide (L3) and N-(4-carboxyphenylmethylene)-4-(4-carboxyphenoxy)-1,8-naphthalimide (H2L4), have been prepared, and their coordination chemistry has been explored in the synthesis of three new coordination polymer materials. Complex poly-[Ag(L3)2]BF4·4.5H2O·0.5THF (1) is a 3-fold 2D → 2D parallel interpenetrated coordination polymer in which three interwoven sheets define inter- and intralayer channels containing anions and solvent molecules. Molecules of L3 interact in 1 through dominant head-to-head π-π stacking interactions, in an opposite aggregation mode to that observed in the free ligand in the crystalline phase. Complexes poly-[Cu(L4)(OH2)]·2DMF·0.5H2O (2) and poly-[Cd2(L4)2(OH2)2]·1.5DMF·3H2O (3) are related noninterpenetrated two-dimensional coordination polymers defined by one-dimensional metal-carboxylate chains, forming layers that interdigitate with adjacent networks through naphthalimide π-π interactions. Both materials undergo structural rearrangements on solvent exchange with acetonitrile; in the case of 3, this transformation can be followed by single-crystal X-ray diffraction, revealing the structure of the acetonitrile solvate poly-[Cd2(OH2)2(L4)2]·2MeCN (4), which shows a significant compression of the primary channels to accommodate the solvent guest molecules. Both materials display modest CO2 adsorption after complete evacuation, and the original expanded phases can be regenerated by reimmersion in DMF. The photophysical properties of each ligand and complex were also explored, which revealed variations in emission wavelength, based on solid-state interactions, including a notable shift in the fluorescence emission band of 3 upon structural rearrangement to 4.

Reversible Phase Transformation in Three Dynamic Mixed-Ligand Metal–Organic Frameworks: Synthesis, Structure, and Sorption Study

Three new dynamic metal–organic frameworks (MOFs) namely {[Cd2(3,4-pyrdc)2(4,4′-bipy)(H2O)2]·4H2O}n (1), {[Mn2(3,4-pyrdc)2(bpee)(H2O)2]·H2O}n (2), and {[Cu2(3,4- pyrdc)2(bpp)2(H2O)4]·5H2O}n (3), based on 3,4-pyridinedicarboxylate (3,4-pyrdc) and three different N,N′-donor ligands [4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethylene (bpee), and 1,3-bis(4-pyridyl)-propane (bpp)] with various divalent transition metal ions have been synthesized and characterized by single-crystal and powder X-ray diffraction and other physicochemical methods. In compounds 1 and 2, the 3,4-pyrdc ligand forms two-dimensional (2D) metal–carboxylate sheets that are connected by N,N′-donor ligands to form three-dimensional (3D) structures with water-filled channels. In compound 3, the 3,4-pyrdc ligand affords one-dimensional metal–carboxylate chains. These chains are connected by the more flexible bpp ligand to form 2D structures, which are extended to a 3D supramolecular architecture by H-bonding. Compounds 1 and 2 show a re...

Lightweight Ionic Networks Composed of Li+ or Mg2+ Centres Linked Together by Dicarboxylate Ligands.

The combination of lightweight metal cations with a range of dicarboxylate ligands has led to the generation of ionic network materials that possess channels occupied by solvent molecules. The compounds [Li2 (2,2-bpdc)(DMF)2 ] and [Mg(2,2-bpdc)(DMF)2 ] (2,2-bpdc=2,2-dipyridyl-4,4-dicarboxylate) adopt a similar structure in which parallel metal-carboxylate chains are linked to four equivalent chains to generate a 3 D network in which DMF molecules occupy channels. [Li4 (3,5-pdc)2 (DMF)]⋅solvate (3,5-pdc=3,5-pyridine dicarboxylate) adopts a similar structure but the chains are more complex. As with the other structures, coordinated DMF molecules occupy network channels. [Li4 (3,5-pdc)2 (DMF)]⋅solvate is able to adsorb carbon dioxide at elevated pressures with the adsorption following a type V isotherm; hysteresis is apparent upon desorption. The final compound, Li[Mg3 OH(2,2-bqdc)3 (DMF/H2 O)3 ]⋅solvate (2,2-bqdc=2,2-biquinoline-4,4-dicarboxylate) has a distinctly different structure in which a trio of magnesium centres bound to a central μ3 -hydroxide ion serves as a 6-connecting, trigonal prismatic node within a 3 D network that has the point symbol, 49 66 . Solvent-filled intraframework spaces represent over 50 % of the crystal volume and are occupied by highly disordered solvent and Li+ ions. Immersion of Li[Mg3 OH(2,2-bqdc)3 (DMF/H2 O)3 ]⋅solvate in a solution of Fe(2,2-bipyridine)3 2+ results in the incorporation of the FeII complex into the large channels of the anionic network.

Diverse Metal–Organic Materials (MOMs) Based on 9,9′-Bianthryl-Dicarboxylic Acid Linker: Luminescence Properties and CO2 Capture

A fluorescent organic linker, namely, 10,10′-bis(4-carboxyphenyl)-9,9′-bianthryl (H2L), was rationally designed and synthesized to access luminescent metal–organic materials (MOMs). A series of structurally diverse MOMs was synthesized with the diacid linker H2L by reacting it with main group, transition, and lanthanide metal ions under different conditions. Among them, Zn-L MOM is a 1D polymeric chain, while Cd-L is a 2D structure in which 4,4′-bipyridyls mediate the formation of 2D networks by linking up the 1D metal–carboxylate chains. The Pb-L MOM is found to be a 2D polymeric net, while Sr-L, obtained under similar reaction conditions, is a noninterpenetrated 3D polymeric structure; the extension from 2D to 3D framework occurs by mediation of Cl– ions. Notably, the reaction of H2L with the lanthanide ions yielded isostructural 3D MOFs, i.e., Tb-L, Eu-L, Sm-L, Nd-L, La-L, Pr-L, Gd-L, and Yb-L, which are noninterpenetrated and porous. The Ln-MOFs are highly robust and stable to solvent exclusion. The r...

Two New Series of Coordination Polymers and Evaluation of Their Properties by Density Functional Theory

Five new coordination polymers (CPs), CPO-68-M (M = Zn, Mn, and Co) and CPO-69-M (M = Ca and Cd), were synthesized by solvothermal methods using 4,4′-dimethoxy-3,3′-biphenyldicarboxylic acid as the organic linker. The three-dimensional frameworks are formed by metal carboxylate chains that are separated by the linker. Structural analysis reveals dense networks with narrow rhombic channels and sra topologies for both CPO-68-M and CPO-69-M. The major structural difference between the two series of CPs is in the metal coordination polyhedra, which are four- and eight-coordinated in CPO-68-M and CPO-69-M, respectively. The CPs are highly crystalline, robust, and have good thermal stability (> 350 °C). On the basis of the topological similarities with MIL-53, we tested whether the CPs would exhibit a similar flexible structure response to gas stimulus. Density functional theory (DFT) modeling was used to evaluate the CPs’ potential as gas adsorption materials over a large range of pressures. The DFT analysis concluded that the CPs are ill-suited for gas adsorption due to their structural rigidity. However, electronic structure calculations reveal that CPO-68-M and CPO-69-M are indirect band gap semiconductors with an estimated band gap between 2.49 and 2.98 eV.

Construction of diverse dimensionality in eight coordination polymers of bivalent metal ions using 5-nitroisophthalate and different linear N,N′-donor linkers

Assembly of 5-nitroisophthalate (nip2−) with first row transition metal salts [Mn(II), Fe(II), Co(II), Zn(II)] in combination with the various neutral auxiliary N,N′-donor linkers, e.g., 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), 1,3-bis(4-pyridyl)propane (bpp) and 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), yielded eight new coordination polymers (CPs), namely {[Mn(4-bpdh)(nip)(H2O)2]·H2O}n (1), {[Fe(4-bpdh)(nip)(H2O)2]·H2O}n (2), {[Co(4-bpdh)(nip)(H2O)2]·H2O}n (3), {[Mn2(bpp)2(nip)2(H2O)2]·H2O}n (4), {[Fe(bpp)(nip)(H2O)]·H2O}n (5), [Zn(bpp)(nip)(H2O)]n (6), {[Fe(4-bpdh)1.5(nip)]·(4-bpdh)0.5}n (7) and {[Fe(4-bpdb)(nip)]·(4-bpdb)0.5(H2O)}n (8) using the slow diffusion technique at room temperature. The complexes 1–8 were characterized by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Complexes 1–3 are isostructural and exhibit a one-dimensional (1D) metal-carboxylate chain with pendant 4-bpdh ligands, which is further extended into a three-dimensional supramolecular structure by means of H-bonding and π–π interactions. Complexes 4–6 are also isomorphous, but distinctly different from the first three complexes. They exhibit a similar 2-fold interpenetrated three-dimensional (3D) net with 66 dia net topology. Compound 7 displays a two-dimensional (2D) grid-like structure, having 4-bpdh ligands in the crystal void, and this is further extended by means of intermolecular π–π interactions into a 3D supramolecular structure, whereas compound 8 possesses a different 2D grid structure containing free 4-bpdb ligands in the void spaces. The thermal stabilities and UV–Vis spectra of all the complexes and the luminescent properties of complex 6 were also studied.

Syntheses, crystal structures and properties of four novel coordination polymers assembled from versatile 1,2,3,5-benzenetetracarboxylic acid

Four novel metal–organic coordination polymers constructed from 1,2,3,5-benzenetetracarboxylic acid, namely [Cu3(Hbtec)2(H2O)6]·2H2O (1), [Co2(btec)(H2O)2] (2), [Zn2(btec)(H2O)2] (3) and [Cd4(btec)2(H2O)5] (4) (H4btec=1,2,3,5-benzenetetracarboxylic acid), have been synthesized by hydrothermal methods and characterized by elemental analysis, IR, TGA and single crystal X-ray diffraction. Complex 1 is a two-dimensional double layer, while three dimensional framework structures are observed for complexes 2–4. The metal atoms are bridged via short connecting μ2-O-carboxylate atoms into dimers in the four different complexes. Interestingly, the dimers connect Hbtec bridged binuclear units into a one dimensional chain and further into a two-dimensional double layer in complex 1, while the metal ions are connected by a short bridge from μ2-O-carboxylate atoms and a long bridge from an adjacent carboxylate into a one dimensional metal carboxylate chain in complexes 2–4. In complexes 2 and 3, each btec ligand is coordinated through three metal carboxylate chains into a metal carboxylate layer, and further into a three-dimensional framework. In complex 4, both a one-dimensional single Cd-carboxylate chain as well as a one-dimensional double Cd-carboxylate chain appear, the two different chains are joined by the ligands into a three dimensional framework. The thermal stabilities and photoluminescent properties of complexes 1–4 were examined. Complexes 3 and 4 display strong room temperature photoluminescence in the visible region, which may be assigned to a ligand-to-metal charge-transfer.

Synthesis and Characterization of Two New Mn(II) Coordination Polymers Containing Different Metal-Carboxylate Chain Motifs

Two Mn(II) coordination polymers, formulated as [Mn(Hhtpa)2(bpa)2(H2O)]n (1) and {[Mn(htpa)(H2O)]·H2O}n (2) (htpa = 4-carboxyphenylacetate, bpa = 1,2-di(4-pyridyl)-ethane), have been synthesized by the hydrothermal reaction and characterized by single-crystal X-ray diffraction, elemental analysis, IR, and thermo-gravimetric analyses (TGA). The structures of both compounds are based on different Mn(II)-carboxylate chain motifs. Complex 1 is a one-dimensional coordination polymer featuring μ2-carboxyl bridged MnO4N2 octahedra. Complex 2 contains Mn-O inorganic chains, featuring μ2-O bridged MnO6 octahedra, which are interconnected further by interchain htpa ligands to form a two-dimensional coordination polymer.

Distinct 3D CdII Coordination Polymers with 1,2-Naphthalenedicarboxylate Regulated by Dipyridyl Co-Ligands with Different Spacers

Two distinct three-dimensional (3D) CdII coordination polymers with 1,2-naphthalenedicarboxylate (ndc2–) and dipyridyl co-ligands have been synthesized under hydrothermal conditions. Interestingly, the slight difference in the two 4,4′-dipyridyl building blocks, namely, 1,2-bi(4-pyridyl)ethane (bpp) and 1,2-bi(4-pyridyl)ethene (bpe) with C–C or C=C spacers, results in the significant structural divergence of the resultant coordination polymers. Structural analysis reveals that complexes [Cd(ndc)(bpp)(H2O)]n (1) and {[Cd5(ndc)4(bpe)2(OH)2](H2O)1.5}n (2) are constructed by discrete metal–carboxylate dimeric units and metal–carboxylate chains, respectively, which are further extended by bpp or bpe linkers to form the inclined interpenetrated two-dimensional (2D)→3D network for 1 and the 3D porous framework for 2. This result reveals that the flexibility of auxiliary ligands plays an important role in the structural assemblies of coordination networks. The thermal and luminescence properties of both complexes were also investigated in solid state.

Syntheses, structures and magnetic properties of four coordination polymers based on nitrobenzene dicarboxylate and various N-donor coligands

Four new coordination polymers {[Ni(4-Nbdc)(bpa)(H2O)]}n (1), {[Co(4-Nbdc)(bpp) (H2O)]}n (2), {[Ni(4-Nbdc)(bpp)(H2O)]·H2O}n (3), and {[Mn2(3-Nbdc)2(bib)3]·2H2O}n (4) (4-Nbdc=4-nitrobenzene-1,2-dicarboxylate, 3-Nbdc=3-nitrobenzene-1,2-dicarboxylate, bpa=1,2-bi(4-pyridyl)ethane, bpp=1,3-bis(4-pyridyl)propane, and bib=1,4-bis(1-imidazoly)benzene), were synthesized by hydrothermal reactions, and characterized by single-crystal X-ray diffractions, elemental analysis, FT-IR, PXRD, TGA and magnetic analysis. Complexes 1 and 2 display quasi-trapezoidal chain and brick-wall layer, and both of them contain metal–carboxylate binuclear units. Complexes 3 and 4 exhibit three-dimensional frameworks with the (66) dia topology and (44.610.8)(44.62) fsc topology, and both of them contain metal–carboxylate chains. The carboxyl groups with syn-anti coordination mode mediate effectively the weak ferromagnetic coupling interaction within Ni(II)–carboxylate binuclear in 1 (J=1.27cm−1) and Ni(II)–carboxylate chain in 3 (J=1.44cm−1), respectively, and the carboxyl groups with anti-anti coordination mode leads to the classic antiferromagnetic coupling interaction within Mn(II)–carboxylate chain in 4 (J=−0.77cm−1).

A novel 3D metal–organic framework constructed from monosubstituted Keggin chains and metal–carboxylate chains

A novel monosubstituted Keggin-type polyoxometalate (POM)-based metal–organic framework [Cu4IICu2I(pzca)6(HPCuMo11O39)(H2O)6]·2H2O (1) (pzca=2-pyrazinecarboxylic acid) has been hydrothermally synthesized and characterized by IR, elemental analysis, TGA and single crystal X-ray diffraction analysis. Compound 1 shows a (2,3,4,7)-connected three-dimensional framework with {4·62·9·102}{4·92}{42·69·87·103}{6·9·10}2{9}2 topology, which is constructed from the monosubstituted Keggin chains [HPCuMo11O39]n4n− and metal–carboxylate chains [Cu6(pzca)6]n4n+. The electrochemical behavior and photocatalytic activity of compound 1 have been investigated.