Synthesis, crystal structure and luminescence properties of two novel lanthanide coordination polymers containing double chain

Two novel lanthanide(III) two-dimensional (2D) coordination polymers [Ln₂(PDC)₂(OH)₂(H₂O)₂] · H₂O (Ln = Eu (1) and Tb (2), H₂PDC = pyridine-3,4-dicarboxylic acid) have been prepared under hydrothermal conditions and characterized by elemental analysis, IR, TGA and single-crystal X-ray diffraction. Compounds 1 and 2 crystallize in the triclinic system, space group , they are isostructural and exhibit the same two-dimensional topological network constructed by PDC-connected Ln-O-Ln double chains. Photoluminescence properties of the compounds 1 and 2 have been investigated in the solid state at room temperature.     

First examples of ternary lanthanide 2,2′-bipyridine-3,3′-dicarboxylate coordination polymers with zigzag chains structures assembled from lanthanide ions, 2,2′-bipyridine-3,3′-dicarboxylate and 1,10-phenanthroline

Four lanthanide coordination polymers, [{Ln₂(bpdc)₃(phen)₂(H₂O)₂} · (H₂O)₆]_n (Ln = Sm (1); Eu (2); Gd (3), Tb (4)), were self-assembled from 2,2′-bipyridine-3,3′-dicarboxylic acid (H₂bpdc),1,10-phenanthroline(phen) and corresponding lanthanide oxides by hydrothermal synthesis. Compounds 1-4 are found to be isomorphous and isostructural. Single-crystal X-ray diffraction studies show that compounds 1-4 are all of one-dimensional zigzag chain structures and extend to two-dimensional networks through π-π interactions and hydrogen bonds. The pyridyl nitrogen atoms of the 2,2′-bipyridyl unit in the bpdc ligand are uncoordinated in an anti-conformation along the central C-C bond of the ligand. Thermogravimetric analysis of 1-4 showed an obvious thermal stability indicating that the coordination habit of the metal ions with bpdc and phen has an effect on the overall framework. Photoluminescence measurement indicates that compound 2 and compound 4 are strong red and green emitters, respectively.     

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.     

2D network coordination polymers of lanthanide with N-(2-pyridylmethyl)iminodiacetic acid: Hydrothermal syntheses, crystal structures and luminescent properties

Six lanthanide two-dimensional network coordination polymers with the general formula of [Ln(pmida)(NO₃)(H₂O)]_n, where Ln = La (1), Nd (2), Sm (3), Gd (4), Dy (5), Er (6) and pmida²⁻ = N-(2-pyridylmethyl)iminodiacetate, have been synthesized by hydrothermal process and characterized by elemental analysis, Infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. All crystals are isostructural and crystallize in the monoclinic space group P2₁/a. The lanthanide(III) ion is nine-coordinated in a geometry of distorted tricapped trigonal prism by two N atoms and two O atoms from one pmida²⁻ ligand, two bridging carboxylate O atoms from other two pmida²⁻ ligands, two O atoms of a bidentate chelating nitrate and a O atom of a coordinated water molecule. The luminescent properties of [Sm(pmida)(NO₃)(H₂O)]_n (3) and [Dy(pmida)(NO₃)(H₂O)]_n (5) were investigated.     

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.     

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.     

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 luminescence properties of five lanthanide-isonicotinate coordination polymers

Five isostructural compounds of lanthanide with isonicotinate ligand, formula as [Ln(IN)₂(H₂O)₄](NO₃) (Ln = La, Nd, Eu, Tb and Er, 1−5, IN = isonicotinate), were synthesized under hydrothermal conditions by tuning the pH level and the ratio of lanthanide with isonicotinic acid. These compounds were characterized by single-crystal X-ray structure analysis, elemental analysis, IR and TG-DTA. In five compounds, the adjacent eight-coordination lanthanide centers were linked together through the bidentate bridging carboxylate groups of isonicotinate ligands to generate infinite chain structures which were further interconnected to form 3D supramolecular networks via the OW-H···N (nitrogen atom came from isonicotinate ligands) and OW-H···O (oxygen atom came from nitrate) hydrogen bonds. Compounds 3 and 4 show strong red and green emission, corresponds to ⁵D₀→⁷F₂ transition of Eu³⁺ ions and ⁵D₄→⁷F₅ transition of Tb³⁺ ions, respectively.     

Syntheses, structures and properties of three cluster-based coordination polymers: influence of the metal ions on the ligand coordination mode and crystal chirality

Three cluster-based coordination polymers, namely [Zn₃(bpy)₃(hip)₂] · 5H₂O (1), [Co₃(bpy)₃(hip)₂] · 5H₂O (2) and [Cd₃(bpy)₃(hip)₂] (3) (bpy=2,2^′-bipyridine, hip=4-hydroxyl-isophthalate) were synthesized and structurally characterized. X-ray single-crystal structural analyses revealed that both 1 and 2 crystallize in the chiral space group P2₁, while 3 crystallizes in the centric space group Pccn. Compounds 1 and 2 are isomorphous and both have (4,4) topological layered structures constructed from trinuclear metal clusters. Compound 3 also shows layered structure of (4,4) topology constructed from trinulear Cd(II) cores. The layers are stacked in a staggered ?ABAB? fashion in 1 and 2 but in an overlapped ?AAA? fashion in 3. There are two types of coordination modes of hip ligand in 1 and 2 but only one in 3. The structural difference between 1 (or 2) and 3 may be attributed to the difference of metal ion nature such as the ionic radius and coordination preference, resulting in the different orientation fashions of the auxiliary bpy ligands, stacking fashions of the layers, as well as chirality of the crystals. The chiral structures of 1 and 2 were also confirmed by measurements of powder second-harmonic-generation (SHG) measurements, which show that 1 and 2 have SHG intensity of 0.50 and 0.02 relative to that of urea, respectively.     

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.     

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.     

Ferrocenesuccinate-bridged lanthanide polymeric complexes: Syntheses, structures and properties

One-dimensional lanthanide-ferrocenesuccinate polymeric complexes [M(η²-FcCOC₂H₄COO)(μ₂-η²-FcCOC₂H₄COO)₂(H₂O)₂]_n (Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₄), M = Pr, 1; Ce, 2; La, 3) have been synthesized and structurally characterized by single-crystal X-ray crystallography. The three polymers are isomorphous, in which each Ln(III) ion is 10-coordinated and connects with two water molecules and eight oxygen atoms from ferrocenesuccinate units in two kinds of coordination modes: bidentate-chelating mode and tridentate-bridging mode. The variable-temperature magnetic susceptibility in the temperature range 5-300 K for 1 and 2 shows that both of them display weak antiferromagnetic interaction. In addition, the redox and fluorescent properties have been investigated. The redox properties are different from the previous results of transition metal compounds containing ferrocenyl systems. Compared with sodium ferrocenesuccinate, polymers 1 and 3, the fluorescent intensities of 2 are markedly enhanced in the solid state.     

Synthesis, crystal structures and magnetic behavior of two 3D coordination polymers using N-(4/3-carboxyphenyl)iminodiacetic acids as bridging ligands

Research on structure and magnetic properties of polynuclear metal complexes to understand the structural and chemical factors governing the electronic exchange coupling mediated by multi-atom bridging ligands is of growing interest. Hydrothermal treatment of Ni(NO₃)₂·6H₂O with N-(4-carboxyphenyl)iminodiacetic acid [N-4(H₃CPIDA)] at 150 °C yielded a 3D coordination polymer of general formula [Ni₃{N-4(CPIDA)}₂(H₂O)₃]·6H₂O (1). An analogous network of general formula [Co₃{N-3(CPIDA)}₂(H₂O)₃]·3H₂O (2) was synthesized using N-(3-carboxyphenyl)iminodiacetic acid [N-3(H₃CPIDA)] in combination with Co(NO₃)₂·6H₂O under identical reaction condition. Both the complexes contain trinuclear secondary building unit, and crystallized in monoclinic system with space groups C2/c (1) and P2₁/c (2), respectively. Variable temperature magnetic characterization of these complexes in the temperature range of 2-300 K indicated the presence of overall ferromagnetic and antiferromagnetic behavior for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) were performed for further insight on the trinuclear units to provide a qualitative theoretical interpretation on the overall magnetic behavior of the complexes 1 and 2.     

Syntheses, structures and properties of three metal pyridinecarboxylates

Three new metal pyridinecarboxylates, namely [Co₂(pydc)₂(H₂O)₅] (1), [Mn(pydc)(H₂O)₂] (2) and [Cd₂(OH)₂(2,4-pydc)] (3), were hydrothermally synthesized. X-ray single crystal structural analysis revealed: 1 and 2 have polymeric one-dimensional chain-like structure constructed by dinuclear cobalt units and Mn-O chains, respectively; 3 has a three-dimensional layer pillared structure constructed from inorganic Cd-O layer and pydc pillars. 1 shows antiferromagnetic interaction but 2 shows alternative antiferromagnetic and ferromagnetic interactions.     

Organic-inorganic hybrid coordination polymers based on tetratopic pyridyl-bridging ligand: Syntheses, structures, and luminescent properties

Employing the symmetrical ligand 1,2,3,4-tetra-(4-pyridyl)-butane (TPB) as bridges, two novel Zn(II) coordination polymers were obtained and characterized by single crystal X-ray diffraction: [Zn(TPB)_0.5(NCS)₂] (1) and [Zn(TPB)(N₃)₂] (2). Polymer 1 features a 2D network with herringbone structural motif constructed by TPB, while polymer 2 shows a dense 3D network connected by TPB and μ_1,3-N₃- bridges. In the former, the TPB ligand acts as a four-connector, while in the latter it acts as four-connector and linear bridge. Both 1 and 2 exhibit strong fluorescent emissions in the solid state, which may be of significance in the field of photoactive materials.     

Synthesis, crystal structure and properties of novel isostructural two-dimensional lanthanide-based coordination polymers with 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid

Five new isostructural two-dimensional lanthanide-based coordination polymers with the formula Ln₂(F₄BDC)₃(DEF)₂(EtOH)₂-2(DEF) (Ln = Tb, 1; Gd, 2; Eu, 3; La, 4; Nd, 5; F₄BDC²⁻ = 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate ligands; DEF = N,N′-diethylformamide), have been synthesized by reaction of Ln(NO₃)₃ and F₄BDC in a DEF/EtOH solvent mixture. The compounds were characterized by single-crystal and powder X-ray diffraction. In all cases, the metal ion is coordinated by nine oxygen atoms from two bidentate μ₂-F₄BDC²⁻ ligands, two bridging μ₂-F₄BDC²⁻ ligands, one μ₃-F₄BDC²⁻ ligand, one DEF molecule and one EtOH molecule forming a tri-capped trigonal prism. The Ln(1) metal ion is linked to an adjacent Ln(1) metal ion through the oxygen atoms of two bridging μ₂-F₄BDC²⁻ ligands and two μ₃-F₄BDC²⁻ bridging ligands to form a Ln₂O₁₈ dimer. The Ln₂O₁₈ polyhedra building units are linked to each other through four F₄BDC²⁻ ligands to form 2D sheets that are held together by hydrogen bonding to form a 3D framework. Compounds 1-5 were further characterized using thermogravimetric analysis and infrared spectroscopy. Studies of the photoluminescence properties of compounds 1 and 3, as well as the catalytic activity of compounds 3-5 in the Biginelli reaction, are presented.     

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.     

Hydrothermal syntheses, crystal structures and topological analyses of four new 3D coordination polymers with mixed ligands

Four new coordination polymers, namely [Ni_1.5(L)(fum)_0.5(mal)(H₂O)]·4H₂O (1), [Zn₂(L)(male)₂]·3H₂O (2), [Ni(L)(adi)_0.5(H₂O)]·0.5(adi)·2.5H₂O (3), and [Zn₂(L)(adi)₂]·5H₂O (4) (L, tetrakis(imidazol-1-ylmethyl)methane; fum, fumarate; mal, malate; male, maleate; adi, adipate) have been synthesized under hydrothermal condition and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. In compound 1, the L, fum, and mal connect the Ni(II) atoms to form a three-dimensional framework. Topologically, the compound shows a trinodal (3,4)-connected (4·10²)(4²·8²·10²)(4²·8⁴) net. Interestingly, the fum and mal came from the configuration transformation and addition reaction of maleate during the synthesis, respectively. In compound 2, the L ligands link the Zn(II) centers to generate a 2D layer, which are further connected by the male ligands to furnish a 3D chrial 4-connected (3·7⁵) net. In compound 3, the adi ligands and the L ligands link the Ni(II) centers to form a 3D framework. Topologically, compound 3 displays a (4,5)-connected net with the Schläfli symbol of (4²·5²·6²)(4²·5³·6⁴·7). In compound 4, the L and adi ligands link the binuclear Zn(II) clusters to yield an intricate 3D (3,6)-connected net with the Schläfli symbol of (4·6²)(4³·6¹²). The fluorescence and thermal stability of complexes 1-4 have also been investigated.     

2D coordination polymers of Nd(III) and Gd(III) with the phenoxyacetate ligand

The self-assembly of anionic phenoxyacetate ligands and Nd(III) cations in a 3:1 ratio leads to a 2D {Nd₂(PhOCH₂COO)₆(H₂O)₃ · H₂O}_n coordination polymer 1, which was structurally characterized. The metal centers are bridged by carboxylic groups to form infinite parallel chains separated (19.4 Å) by the π-π and C-H?π-stacked phenoxy groups of the ligands. The thermal dependence of the molar magnetic susceptibility for the isostructural gadolinium polymer 2 has been measured and analyzed according to the analytical expression of an infinite chain of classical spins derived by Fisher. The Gd?Gd interaction is ferromagnetic with a magnitude of 0.015(3) cm⁻¹. Modelling of the field-dependent magnetization at 2 K corroborates this result.     

Structure and luminescence of sodium and lanthanide(III) coordination polymers with pyridine-2,6-dicarboxylic acid

A series of coordination polymers constructed by sodium, lanthanide(III), and pyridine-2,6-dicarboxylate (dipic),NaLn(dipic)₂ · 7H₂O (Ln = Eu, Gd, Tb), have been prepared under a hydrothermal condition. The crystal structures of the three compounds which are isostructual were determined by single-crystal X-ray diffraction. The two-dimensional layers found in the compounds are built up from six-folded {NaO₆} polyhedra and nine-folded {LnN₂O₇} polyhedra, these being edge-shared each other along the c axis and bridged by carboxylate groups of dipic along the b axis, respectively. This two-dimensional framework provides cavities inside the layer and interlayer spaces outside the layer for accommodation of the two dipic molecules coordinated to a lanthanide(III) ions. The dehydrated materials obtained by heating the as-synthesized crystals at 200 °C held their crystal structure, and absorbed the same amounts of water molecules as those of the as-synthesized crystals upon the exposure of 100% relative humidity at room temperature. The Eu and Tb compounds showed strong red and green emissions, respectively, due to an energy transfer from dipic molecules to trivalent emission ions.