Lanthanide-based Coordination Polymers Research Articles

Structure control and crystal-to-crystal transformation for two series of lanthanide–organic coordination polymers

Two series of lanthanide-based coordination polymers, [Ln(HCPOB)(CPOB)(H2O)2]n [Ln = Eu(a1), Gd(a2), Tb(a3), Dy(a4), Ho(a5), Er(a6)] and [Ln(HCPOB)(CPOB)]n [Ln = Eu(b1), Gd(b2), Tb(b3), Dy(b4), Ho(b5), Er(b6)], have been synthesized using an asymmetric semi-rigid V-shape multicarboxylate ligand [H4CPOB = 2-(4-carboxyphenoxy)benzoic acid] by a hydrothermal method at different temperatures. Series a were obtained at 130 °C and have one-dimensional (1D) chain architectures, while series b were synthesized at 180 °C and exhibit three-dimensional (3D) structures. Interestingly, temperature-dependent XRD patterns for 1D compounds indicate that the 1D structure changes to form the 3D coordination polymers on heating the crystals. Single crystals of series a can transform into crystals of series b without any significant change in crystal quality. The variations from 1D to 3D coordination structures are attributed to variable coordination modes of multicarboxylate ligand H2CPOB. In addition, we have studied the luminescent properties of Eu3+, Tb3+, and Dy3+ compounds of series a and series b, and found that series a give very weak luminescence because of coordinated water molecules existing in the complexes. Due to the “antenna effect” or “luminescence sensitization”, series b exhibit much stronger fluorescent intensity than that of series a.

1,2,4,5-Benzene-tetra-carboxylic acid: a versatile ligand for high dimensional lanthanide-based coordination polymers

Reactions in water between 1,2,4,5-benzene-tetra-carboxylate and lanthanide ions lead to seven families of lanthanide-containing coordination polymers with respective chemical formulae {[Tm4(btec)3(H2O)10]·7H2O}∞ (Family 1), {[Ln4(btec)3(H2O)10]·16H2O}∞ with Ln = Ho and Tm (Family 2), {[Ln4(btec)3(H2O)12]·12H2O}∞ with Ln = Er, Tm and Y (Family 3), {[Ln4(btec)3(H2O)12]·11H2O}∞ with Ln = Er, Tm and Y (Family 4), {[Gd4(btec)3(H2O)14]·14H2O}∞ (Family 5), {[Ln5(btec)3(Hbtec)(H2O)12]}∞ with Ln = Eu and Gd (Family 6) and {[KGd5(btec)4(H2O)13]·11H2O}∞ (Family 7). All these compounds have been obtained by slow diffusion through water or gel media. They have been structurally characterized. Six out of the seven families are three-dimensional and their potential porosities have been estimated by a computational method. Compounds that belong to families 2, 4 and 6 present a potential porosities of 1281 m −1, 1156 m2 g−1 and 836 m2 g−1, respectively.

Syntheses, structures, photoluminescence and magnetic properties of four-connected lanthanide–tricarboxylate coordination polymers

Ten novel lanthanide-based coordination polymers {[LnL(H2O)2]·H2O}n (Ln = Pr (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Yb (9), and Lu (10), H3L = 2-(carboxylmethoxy)terephthalic acid), have been successfully synthesized through hydrothermal reactions of corresponding Ln(OH)3 with semirigid tricarboxylate H3L ligands. Compounds 1 and 2 are isostructural, containing a 3D porous framework built of carboxylate-bridged layers with 66-topology, while 3–10 display the same 2D double-layer structure based on binuclear Ln2O2 units with 43·63-topology. The PXRD and TGA prove their phase purity and high thermal stability, respectively. Photoluminescent studies indicate the efficient energy transfer from L3− ligand to Ln3+ ions, exhibiting the typical intense emissions of corresponding Ln3+ ions in the visible region. The magnetic exchange interactions also are studied in compounds 4–7 for their short O bridges between Ln3+ ions, and the results show that there may be ferromagnetic interactions in 4–6, while in 7 the interactions cannot be distinctly deduced from the curves due to the nature of the Ho3+ ions. Furthermore, compound 6 displays slow magnetization relaxation, exhibiting single-molecule magnetic behavior.

Facile fabrication of Y4(1,2-BDC)6(H2O)2·5H2O:Eu3+,Tb3+ ultralong nanobelts and tunable luminescence properties

Lanthanide-based coordination polymer yttrium 1,2-benzenebicarboxylate ultralong nanobelts have been successfully prepared through a simple and mild one-step approach on a large scale. Electron microscopy images show that the uniform nanobelts are about 100–150 nm in width, 20–40 nm in thickness and up to several hundreds of micrometers in length. The crystal structure of the obtained nanobelts belongs to the triclinic crystal system with space group P1. The exact chemical composition was obtained by X-ray powder diffraction (XRD), elemental analysis, thermal gravimetric analysis (TGA) and Fourier-transform infrared spectra (FT-IR). The ultralong nanobelts growth was explored by time-dependent experiments and a possible formation mechanism was proposed. The investigation of the luminescent properties reveals that the luminescence colors of yttrium 1,2-benzenebicarboxylate nanobelts co-doped with Tb3+ and Eu3+ ions under ultraviolet light can be tuned from green, through green–yellow and yellow, to red by changing the relative doping concentration of the activator ions. It is expected that the synthetic strategy can be used to prepare other nanoscale metal–organic frameworks.

Gas sorption and luminescence properties of a terbium(iii)-phosphine oxide coordination material with two-dimensional pore topology

The structure, stability, gas sorption properties and luminescence behaviour of a new lanthanide-phosphine oxide coordination material are reported. The polymer PCM-15 is based on Tb(III) and tris(p-carboxylated) triphenylphosphine oxide and has a 5,5-connected net topology. It exhibits an infinite three-dimensional structure that incorporates an open, two-dimensional pore structure. The material is thermally robust and remains crystalline under high vacuum at 150 °C. When desolvated, the solid has a CO(2) BET surface area of 1187 m(2) g(-1) and shows the highest reported uptake of both O(2) and H(2) at 77 K and 1 bar for a lanthanide-based coordination polymer. Isolated Tb(III) centres in the as-synthesized polymer exhibit moderate photoluminescence. However, upon removal of coordinated OH(2) ligands, the luminescence intensity was found to approximately double; this process was reversible. Thus, the Tb(III) centre was used as a probe to detect directly the desolvation and resolvation of the polymer.

Lanthanide-Based Coordination Polymers Assembled from Derivatives of 3,5-Dihydroxy Benzoates: Syntheses, Crystal Structures, and Photophysical Properties

Two new aromatic carboxylic acids, namely, 3,5-bis(benzyloxy)benzoic acid (HL1) and 3,5-bis(pyridine-2-ylmethoxy)benzoic acid (HL2), have been prepared by replacing the hydroxyl hydrogens of 3,5-dihydroxy benzoic acid with benzyl and pyridyl moieties, respectively. The anions derived from HL1 and HL2 have been used for the support of a series of lanthanide coordination compounds [Eu(3+) = 1-2; Tb(3+) = 3-4; Gd(3+) = 5-6]. The new lanthanide complexes have been characterized on the basis of a variety of spectroscopic techniques in conjunction with an assessment of their photophysical properties. Lanthanide complexes 2, 4, and 6, which were synthesized from 3,5-bis(pyridine-2-ylmethoxy)benzoic acid, were structurally authenticated by single-crystal X-ray diffraction. All three complexes were found to exist as infinite one-dimensional (1-D) coordination polymers with the general formula {[Ln(L2)(3)(H(2)O)(2)]·xH(2)O}(n). Scrutiny of the packing diagrams for 2, 4, and 6 revealed the existence of interesting two-dimensional molecular arrays held together by intermolecular hydrogen-bonding interactions. Furthermore, the coordinated benzoate ligands serve as efficient light harvesting chromophores. In the cases of 1-4, the lowest energy maxima fall in the range 280-340 nm [molar absorption coefficient (ε) = (0.39-1.01) × 10(4) M(-1) cm(-1)]. Moreover, the Tb(3+) complexes 3 and 4 exhibit bright green luminescence efficiencies in the solid state (Φ(overall) = 60% for 3; 27% for 4) and possess longer excited state lifetimes than the other complexes (τ = 1.16 ms for 3; 1.38 ms for 4). In contrast to the foregoing, the Eu(3+) complexes 1 and 2 feature poor luminescence efficiencies.

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 Ln 2(F 4BDC) 3(DEF) 2(EtOH) 2-2(DEF) (Ln = Tb, 1; Gd, 2; Eu, 3; La, 4; Nd, 5; F 4BDC 2− = 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate ligands; DEF = N,N′-diethylformamide), have been synthesized by reaction of Ln(NO 3) 3 and F 4BDC 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 μ 2-F 4BDC 2− ligands, two bridging μ 2-F 4BDC 2− ligands, one μ 3-F 4BDC 2− 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 μ 2-F 4BDC 2− ligands and two μ 3-F 4BDC 2− bridging ligands to form a Ln 2O 18 dimer. The Ln 2O 18 polyhedra building units are linked to each other through four F 4BDC 2− 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.

Fabrication of size-controllable and luminescent dysprosium benzenetricarboxylate nanobelts at room temperature

Lanthanide-based coordination polymer Dy(1,3,5-BTC)(H 2O) 6 nanobelts were successfully synthesized on a large scale through an extremely simple approach at room temperature; the size of the nanobelts can be easily tuned from several to several hundred micrometers in length, 70–600 nm in width, and 10–100 nm in thickness by varying concentrations, solvent, and surfactant reasonably. In addition, the as-obtained dysprosium benzenetricarboxylate nanobelts exhibit the characteristic emission of the Dy 3+ ions, making the belt-like coordination polymer have potential applications in building minioptoelectronic devices.

Synthesis, structure and property of serial p-carboxylphenoxyacetate-lanthanide coordination polymers

Four novel lanthanide-based coordination polymers, [Ln(PBDC)(HPBDC)(H2O)3] (H2PBDC=p-carboxylphenoxyacetate; Ln = La (1), Pr (2), Nd (3)) and [La2(PBDC)3(H2O)4] (4), have been prepared through hydrothermal synthetic methods. Compounds 1–3 are isomorphous and exhibit one-dimensional (1D) chain-like motifs, while compound 4 features a complicated three-dimensional (3D) architecture, which is designed and synthesized based on the inspiration from the structure characterization of compound 1. Under the similar reaction conditions, the carboxyl in compound 1 may be further deprotonated by adding the organic base of 2,2′-bipyridine. This subtle change caused a significant difference in the structures, from 1D chain of 1 to a 3D structure of 4. In addition, IR, UV-Vis, TGA and magenetic properties are also investigated in this paper.

Constructions of a Set of New Lanthanide-Based Coordination Polymers with Hatza Ligands (Hatza = 5-Aminotetrazole−1-Acetic Acid)

Reaction of LnCl3·6H2O with 5-aminotetrazole-1-acetic acid (Hatza) under the presence of KOH produced a set of new Ln(III)/atza complexes, [Ln(atza)2(CH3OH)(H2O)Cl][Ln = Pr (1), Nd (2), Sm (3)], [Ln(atza)2 (H2O)3]Cl [Ln = Eu (4), Gd (5)], and [Tb(atza)2(H2O)4]Cl (6). These compounds were structurally characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. The complexes 1−3 are isostructural and display two-dimensional frameworks, the isostructural complexes 4−5 show one-dimensional (1D) structures, and complex 6 forms a 1D framework. Furthermore, the luminescence properties of 4 and 6 were investigated at room temperature in the solid state.

In situ cyclodehydration of iminodiacetic acid into 2,5-diketopiperazine-1,4-diacetate in lanthanide-based coordination polymers

The reaction of iminodiacetic acid with Ln2O3 (Ln = Dy, Ho, Er, Yb) under hydrothermal conditions generate a series of 3D lanthanide-based coordination polymers, in which, the iminodiacetic acid (IDA) was transformed into a 2,5-diketopiperazine-1,4-diacetate.

Structural and Luminescent Properties of Micro- and Nanosized Particles of Lanthanide Terephthalate Coordination Polymers

Reaction in water between rare earth ions (Ln = Y, La-Tm, except Pm) and the sodium salt of terephthalic acid leads to a family of lanthanide-based coordination polymers of general formula [Ln2(C8H4O4)3(H2O)4] n with Ln = La-Tm or Y. The isostructurality of the compounds with the previously reported Tb-containing polymer is ascertained on the basis of their X-ray powder diffraction diagrams. The coordination water molecules can be reversibly removed without destroying the crystal structure for compounds involving one of the lighter lanthanide ions (La-Eu). For compounds involving one of the heavier lanthanide ions (Tb-Tm) or yttrium, a structural change occurs during the drying process. X-ray diffraction data show this new anhydrous phase corresponding to the linking of pairs of Er(III) ions through mu-carboxylate bridges. Porosity profiles calculated for the anhydrous phases of Tb(III) and Er(III) show the presence of channels with very small sections. The luminescent properties of all the compounds have been recorded and the two most luminescent polymers, namely, the europium- and the terbium-containing ones, have been studied in more detail. Tb(III)-containing compounds display large quantum yields, up to 43%. Polyvinylpyrrolidone nanoparticles doped with [Ln2(C8H4O4)3(H2O)4] n (Ln = Eu, Tb, Er) have also been synthesized and characterized. The encapsulation of the coordination polymers results in somewhat reduced luminescence intensities and lifetime, but the nanoparticles can be dispersed in water and remain unchanged in this medium for more than 20 h.

Tunable Luminescent Lanthanide Coordination Polymers Based on Reversible Solid-State Ion-Exchange Monitored by Ion-Dependent Photoinduced Emission Spectra

A new family of porous lanthanide-based coordination polymers with tunable luminescent properties based on reversible ion-dependent exchange was reported.

New lanthanide based coordination polymers with high potential porosity

Abstract Reaction in an aqueous gel medium between a lanthanide ion and the sodium salt of the naphthalene-tetra-carboxylic acid can lead to coordination polymers. We report here the synthesis, the crystal structure and the calculated porosity of the first two new coordination polymers, namely Gd[(C10H4)(COO)3(COOH)](H2O)4·9H2O and Er4[(C10H4)(COO)4]3(H2O)10·12H2O. The first compound crystallizes in the triclinic system, space group P 1 ¯ (no. 2) with a = 6.4456(1) A, b = 12.0131(3) A, c = 16.4256(4) A, α = 107.8706(9)°, β = 97.0735(9)°, γ = 93.4771(15)° and Z = 2. The crystal structure can be described as wavy planes strongly connected to each other by hydrogen bonds. This pseudo 3D crystal structure presents very large rectangular channels filled by crystallization water molecules. The second compound crystallizes in the monoclinic system, space group P21/c (no. 14) with a = 9.8442(1) A, b = 29.2288(2) A, c = 10.8795(1) A, β = 92.1767(3)° and Z = 4. Its crystal structure is 3D and presents some large channels with rectangular sections. These channels are full of crystallization water molecules. In both cases, the crystallization water molecules have been formally removed and the porosity has been calculated using Connolly's algorithm. Both present a rather high potential porosity.

A new family of luminescent lanthanide based coordination polymers

Reaction in water between a lanthanide ion (Ln = Sm–Dy) and the sodium salt of isophthalic acid leads to a new family of lanthanide-based coordination polymers. The crystal structure has been solved on the basis of the Gd containing compound. The iso-structurality of the other compounds has been assumed on the basis of powder X-ray diffraction diagrams. These compounds of general formula Ln2(OH)(C8H4O4)2(C8H5O4)(H2O)8·6H2O crystallize in the monoclinic system, space group P21/a (no. 14) with a = 17.4249(2) Å, b = 10.9148(1) Å, c = 20.7216(2) Å, β = 113.1694(4)° and Z = 4. This crystal structure is 1-D. Chains are bound to each other by hydrogen bonds. The thermal stability of these compounds is described and discussed as well as luminescent properties of the coordination polymers involving luminescent rare earth ions.

Structuring effects of [Ln6O(OH)8(NO3)6(H2O)12]2+ entities

In order to obtain highly porous lanthanide-based coordination polymers we are currently investigating reactions between [Ln6O(OH)8(NO3)6(H2O)12]2+ di-cationic hexanuclear entities and sodium salts of benzene-poly-carboxylic acids. Two new coordination polymers obtained during this study are reported here. In both cases, the hexanuclear entity has been destroyed during the reaction. However the resulting compounds are original thanks to a structuring effect of the poly-metallic complex. The first compound of chemical formula [Y2(C8H4O4)3(DMF)(H2O)],2DMF crystallizes in the monoclinic system, space group P121/n (n°14) with a = 16.0975(3) Å, b = 14.4605(3) Å, c = 17.7197(4) Å, β = 92.8504(9)° and Z = 4. The second compound of chemical formula Y2(NO3)2(C10H2O8)(DMF)4 crystallizes in the triclinic system, space group P-1 (n°2) with a = 7.5312(3) Å, b = 9.0288(3) Å, c = 13.1144(6) Å, α = 92.6008(14)°, β = 94.9180(14)°, γ = 112.1824(16)° and Z = 2. Both crystal structures are 2D. Both crystal structures are described and the original structural features are highlighted and related to a potential structuring effect of the hexanuclear precursor.

Two- and Three-Dimensional Lanthanide Complexes: Synthesis, Crystal Structures, and Properties

3,5-pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1-9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal-organic framework structures. The complexes {[Ln2(HL)3(H2O)4].2H2O}n (Ln=Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3].3H2O}n (Ln=Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln=Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoledicarboxylic acid were observed, which proved that 3,5-pyrazoledicarboxylic acid may be used as an effective bridging ligand to assemble lanthanide-based coordination polymers. The photophysical and magnetic properties have also been investigated.

{[Nd4(ox)4(NO3)2(OH)2(H2O)2]·5H2O}n: A Porous 3D Lanthanide-Based Coordination Polymer with a Special Luminescent Property

Unique bridging modes of oxalates and nitrates have unexpectedly caused a porous 3D lanthanide-based coordination polymer, which has 1D channels and displays a special luminescent property.

Syntheses, structures and luminescent properties of new lanthanide-based coordination polymers based on 1,4-benzenedicarboxylate (bdc)

Reaction of 1,4-benzenedicarboxylic acid (1,4-H2BDC) with EuCl(3).6H2O in MeOH in the presence of Et3N and MeCN gives a mixture of the 3-D metal-organic-framework (MOF) materials [Eu2(1,4-BDC)3(MeOH)4].8MeOH (1) and 2-D [Eu(1,4-BDC)(MeOH)4].Cl.MeOH.0.25H2O (2). Similar reactions afforded the isomorphous Gd (3) and Tb (4) analogs of 2. Reaction of 1,4-H2BDC with Ln(NO3)(3).6H2O under similar conditions gave [Ln(BDC)NO3(MeOH)2].MeCN.H2O (Ln = Eu (5) and Gd (6)), which have 2-D framework structures. The structures of 1-6 were determined by single crystal X-ray crystallographic studies and the luminescence properties of 1 and 4 in DMF solution were determined.