Lanthanide Coordination Polymers Research Articles

Effective Europium Coordination Luminophores Linked with Bi- and Tridentate Carbazole Phosphine Oxides for Organic Electroluminescent Devices

Lanthanide coordination polymers with charge combination parts, hole and electron transport units, [Eu(ntfa)3(dppcz)]n and [Eu3(ntfa)9(tpcz)2]n [ntfa = 3-(2-naphthoyl)-1,1,1-trifluoroacetonate, dppcz = 3,6-bis(diphenylphosphoryl)-9-phenylcarbazole), tpcz = 3,6-bis(diphenylphosphoryl)-9-[4-(diphenylphosphoryl)phenyl]carbazole], are reported as an emitting material for organic electroluminescent (EL) devices. The intrinsic emission quantum yields Φ4f–4f of [Eu(ntfa)3(dppcz)]n and [Eu3(ntfa)9(tpcz)2]n in the solid state were calculated to be 32% and 45%, respectively. The photosensitized energy-transfer efficiencies ηsens from organic ntfa ligands to luminescent Eu(III) ions in [Eu(ntfa)3(dppcz)]n and [Eu3(ntfa)9(tpcz)2]n were found to be 84% and 39%, respectively. The energy-transfer efficiency ηsens from ntfa to Eu(III) ion is dependent on the network structure in Eu(III) coordination polymers in the solid state. The ηsens values and characteristic structures of Eu(III) coordination polymers are directly l...

Series of Highly Stable Lanthanide-Organic Frameworks Constructed by a Bifunctional Linker: Synthesis, Crystal Structures, and Magnetic and Luminescence Properties.

By utilizing a preselected functional ligand produced by 1 H-imidazole-4,5-dicarboxylic acid, three isostructural lanthanide coordination polymers (CPs), denoted as {[Ln2(OH)2(L)2]·(DMF)·(H2O)4} n (Ln = Gd (1), Eu (2), Dy (3); L = 1-(4-carboxybenzyl)imidazole-4-carboxylic acid), containing a 1D infinite [Ln4(OH)4] subchain have been successfully constructed. The highly connected mode between the multifunctional ligand and 1D building units is responsible for the exceptional chemical stability of three lanthanide CPs. In addition, a study of the magnetic properties reveals that 1 displays a large magnetic entropy change (-Δ Sm = 30.33 J kg-1 K-1 with T = 2 K and Δ H = 7 T). Furthermore, genetic algorithm and quantum Monte Carlo methods were combined to simulate the magnetic coupling parameters of compound 1, shedding light on the effect of linking bridges on magnetic propagation. 2 shows intense luminescence in the range of 350-710 nm. Comparably, magnetic studies of 3 reveal the existence of a metamagnetic transformation from an antiferromagnetic interaction to a ferromagnetic interaction along with a decrease in temperature. Through fitting of the results of HF-EPR measurements, a component of the g tensor is obtained, g|| = 16.4(5), indicating the large anisotropy of 3.

Novel hybrid materials of lanthanide coordination polymers ion exchanged Mg-Al layered double hydroxide: Multi-color photoluminescence and white color thin film

In the context, pillared layered hybrid materials Ln(PDA)33—LDH are prepared through ion exchange assembly of luminescent lanthanide coordination polymers [H2NMe2]3[Ln(DPA)3] (Ln = Eu, Tb, Sm, Dy, Nd; [H2NMe2]+ = dimethyl amino cation; H2DPA = 2,6-dipicolinic acid) and pillared layered double hydroxide (Mg6Al2(OH)16CO3·4H2O). Among Mg-Al LDH interacts with [H2NMe2]3[Ln(DPA)3] through anion exchange ([Ln(PDA)3]3-) and electrostatic effect to form [Ln(PDA)3]3--LDH. All these hybrids display the typical Ln3+ emission. By controlling the composition of different Ln3+ cations in hybrid systems, the luminescent color can be tuned and the white light output can be realized. Furthermore, with careful adjustment of the excitation wavelength, the color of the luminescence can be modulated. Moreover, the white light emissive thin film based on the [Dy/Eu(PDA)3]3--LDH are prepared in order to extend their potential application, which displays desirable white light.

Syntheses, Structures, and Photoluminescence of Lanthanide Coordination Polymers Based on 4‐Oxo‐1,4‐dihydro‐2,6‐pyridinedicarboxylic acid

Investigating the coordination chemistry of H2CDA (4‐oxo‐1,4‐dihydro‐2,6‐pyridinedicarboxylic acid) with rare earth salts Ln(NO3)3 under hydrothermal conditions, structure transformation phenomenon was observed. The ligand, H2CDA charged to its position isomer, enol type structure, H3CAM (4‐hydroxypyridine‐2,6‐dicarboxylic acid). Six new lanthanide(III) coordination polymers with the formulas [Ln(CAM)(H2O)3]n [Ln = La (1), Pr, (2)] and {[Ln(CAM)(H2O)3]·H2O}n [Ln = Nd, (3), Sm, (4), Eu, (5), Y, (6)] were synthesized and characterized. The X‐ray structure analyses show two kinds of coordination structures. The complexes 1 and 2 and 3–6 are isostructural. Complexes 1 and 2 crystallize in the monoclinic C2/c space group, whereas 3–6 crystallize in the monoclinic system with space group P21/n. In the two kinds of structures, H3CAM displays two different coordination modes. The SmIII and EuIII complexes exhibit the corresponding characteristic luminescence in the visible region at an excitation of 376 nm.

Lanthanide Coordination Polymers of Mixed Phthalate/Adipate for Ratiometric Temperature Sensing in the Upper-Intermediate Temperature Range.

Based on the mixed phthalate (phth2-) and adipate (ad2-), [Nd2(ad)(phth)2(H2O)4] (I) and [Ln(ad)0.5(phth)(H2O)2] (Ln = EuIII (II), GdIII (III), TbIII (IV), DyIII (V), ErIII (VI), TmIII (VII), 1EuIII:10TbIII (VIII), 3EuIII:10TbIII (IX), and 5EuIII:10TbIII (X)) were synthesized and characterized. Complexes VIII-X show excellent ratiometric temperature sensing behavior in physiological and higher temperature ranges (303-423 K) rendered by the TbIII-to-EuIII energy transfer process. The efficiency of the process as illustrated through the lifetime measurements depends on both the EuIII:TbIII mole ratio and the temperature. The performance of X in terms of relative sensitivity ( Sr), temperature resolution, and measurement repeatability were determined, revealing the maximum Sr ( Sm) of 1.21%·K-1 at 303 K with reliable temperature resolution and excellent repeatability.

Front Cover: Coordination Polymers based on the Neutral Ditopic Ligand (C6H4PO(OCH3)2)2 Involving some f‐Block Elements (Z. Anorg. Allg. Chem. 3/2018)

Going up! The cover picture alludes to a landmark in Kassel, the man walking to the sky, illustrating how molecular structures may serve as tools for accessing higher dimensions. Our work describes selected lanthanide, calcium and uranium coordination polymers built from an easy accessible bisphosphonic ester ligand; several show intriguing network topologies covering one- to two-dimensional networks and macrocyclic units containing laterally assembled π-systems, with efficient quenching of the uranium emission. Details are discussed in the article by Kristijan Krekić, Eireen Käkel, Dieter Klintuch, Dana Bloß and Rudolf Pietschnig on page 149 ff.

Ratiometric fluorescence sensing of mercuric ion based on dye-doped lanthanide coordination polymer particles

This work focused on the development of a novel ratiometric fluorescence sensor for detection of Hg2+ by using dye-doped lanthanide infinite coordination polymer (Ln-ICP) particles. The dye-doped Ln-ICP used herein was prepared by self-assemble of adenosine monophosphate (AMP) with Ce3+ and Tb3+ (Ce/Tb-AMP) through self-adaptive chemistry, in which the fluorescent dye coumarin was encapsulated during the assembly process as a guest molecule. Under 310 nm irradiation, the obtained coumarin@Ce/Tb-AMP itself emitted characteristic green luminescence of Tb3+, accompanied with a weak fluorescence at 445 nm originated from coumarin encapsulated in the Ce/Tb-AMP networks. The fluorescence emission of coumarin became strong when it was released to the solution. In the presence of Hg2+, the coumarin@Ce/Tb-AMP was destroyed due to the specific coordination interaction between AMP and Hg2+, which leaded to the release of coumarin to the solution meanwhile. Consequently, the fluorescence of Ce/Tb-AMP was quenched, while that of coumarin enhanced. On the basis of this strategy, we developed a novel ratiometric fluorescent sensor for the detection of Hg2+ by measuring the ratio of fluorescent intensity of the coumarin@Ce/Tb-AMP suspension, which showed a wide linear range from 0.08 to 1000 nM and detection limit of 0.03 nM with high selectivity and sensitivity. Furthermore, the constructed ratiometric fluorescent sensor was successfully applied in detecting Hg2+ in drinking water and human blood serum (HBS) with satisfactory results.

Enhancing luminescence in lanthanide coordination polymers through dilution of emissive centers

A Ln-adipate metal-organic framework templated with 4,4′-bipyridine (GWMOF-6) was synthesized with Eu(III) or Tb(III) ions with various concentrations of optically inert Gd(III) ion in order to evaluate the effects of diluting the emissive metal center on the efficiency of luminescence. The doping ratios of Ln:Gd (Ln = Eu or Tb) showed that of the ratios studied, the 50:50 system had among the highest quantum yields (Eu = 3.9%, Tb = 7.6%) with increasing lifetimes as Gd(III) concentration increased. A 50:50 Eu:Tb system was also synthesized and showed to be more efficient than the Eu:Gd systems (Φ = 15.3%), with an exceptionally high energy transfer efficiency (80%) from the 5D4 state of the Tb(III) ion to the 5D1 and 5D0 energy levels of the Eu(III) ion.

A Eu/Tb mixed lanthanide coordination polymer with rare 2D thick layers: Synthesis, characterization and ratiometric temperature sensing

A series of lanthanide coordination polymers LnBTPTA (Ln = Eu, Tb, EuxTb1−x), was synthesized using a tricarbocylic ligand 4,4′,4′′-(benzene-1,3,5-triyltris(1H-pyrazole-3,1-diyl))tribenzoic acid (H3BTPTA). X-ray single crystal analyses reveal that the asymmetric unit cell contains seven crystallographically independent metal ions and seven crystallographically independent ligands which is quite unusual. The 3D framework is comprised of 2D thick layers stacked through van der Waals force, π-π interactions and hydrogen bonding interactions. Eu0.0316Tb0.9684BTPTA presents a dual-emission of Tb3+ at 543nm and Eu3+ at 617nm, and the intensity ratio shows an excellent linear relationship with the temperature changing in 25–225K. The relative sensitivity 0.45–5.12%K−1 is much higher than those have been reported in the same detection range.

Rare earth niobate coordination polymers

Rare-earth (RE) coordination polymers are infinitely tailorable to yield luminescent materials for various applications. Here we described the synthesis of a heterometallic rare-earth coordination compound ((CH3)2SO)3(RE)NbO(C2O4)3((CH3)2SO) = dimethylsulfoxide, DMSO, (C2O2= oxalate), (RE=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb). The structure was obtained from single crystal X-ray diffraction of the La analogue. The Nb˭O and DMSO terminal-bonding character guides assembly of an open framework structure with noncentrosymmetric RE-coordination geometry, and large spacing between the RE centers. A second structure was observed by PXRD for the smaller rare earths (Dy, Ho, Er, Yb); this structure has not yet been determined. The materials were further characterized using FTIR, and photoluminescence measurements. Characteristic excitation and emission transitions were observed for RE = Nd, Sm, Eu, and Tb. Quantum yield (QY) measurements were performed by exciting Eu and Tb analoges at 394nm (QY 66%) and 464nm (QY 71%) for Eu; and 370nm (QY=40%) for Tb. We attribute the high QY and bright luminescence to two main structure-function properties of the system; namely the absence of water in the structure, and absence of concentration quenching.

A water-stable lanthanide coordination polymer as a multiresponsive luminescent sensor for Fe3+, Cr(vi) and 4-nitrophenol.

Constructing water stable lanthanide coordination polymers (Ln-CPs) is of great importance for practical applications in biological and environmental areas and necessary for systematic research on the relationship between the properties of Ln-CPs and structures of linker ligands. A two-dimensional (2D) Eu coordination polymer (Eu-CP) {[Eu(L)(HCOO)]·H2O}n (H2L = isomer of 5-((pyridin-3-yloxy)methyl)isophthalic acid) is synthesized by the reaction of Eu(NO3)3·6H2O and H2L and heating at 140 °C. Single crystal X-ray diffraction analysis indicates that the Eu-CP presents a 2D network structure formed by binuclear metal clusters and bridged linkers COO- and HCOO-. The luminescence properties of the Eu-CP are explored at room temperature in the solid-state. The Eu-CP emits bright and stable red light due to the antenna effect from the ligand to the metal ion. The characteristic emission peaks of Eu3+ can be observed in its spectra. The luminescence intensity of the Eu-CP can be sensitively quenched by inorganic ions Fe3+, CrO42-, and Cr2O72- and the organic molecule 4-nitrophenol (4-NP). The Eu-CP can be a multiresponsive luminescent sensor in the water phase. Solvent luminescence investigation and PXRD data demonstrate that the Eu-CP exhibits excellent water stability. Therefore, all the sensing experiments are carried out in the water system. This multi-responsive luminescent sensor can detect Fe3+, Cr(vi) or 4-NP with high sensitivity and low detection limits in aqueous solution. Furthermore, the mechanism for the selective sensing of Fe3+, Cr(vi) or 4-NP is also explored which can mainly be explained by energy competition between the absorption of the analytes and the excitation of the Eu-CP.

Structure, color-tunable luminescence, and UV-vis/NIR benzaldehyde detection of lanthanide coordination polymers based on two fluorinated ligands

A series of 1D lanthanide coordination polymers exhibits white-light emission and detects benzaldehyde in the UV-visible and NIR region.

Temperature-dependent 3D structures of lanthanide coordination polymers based on dicarboxylate mixed ligands

Four families of fourteen three-dimensional (3D) lanthanide coordination polymers (CPs) with dicarboxylate mixed ligands have been synthesized hydrothermally at different temperatures.

General strategy for lanthanide coordination polymers constructed from 1,1′-ferrocenedicarboxylic acid under hydrothermal conditions

26 lanthanide CPs were synthesized under different reaction conditions. As well, their fluorescence and magnetism properties were investigated.

The role of structure and the metal ion in the fluorescence sensing of nitro compounds for a series of lanthanide(iii) 9,10-anthracene dicarboxylate coordination polymers.

Twenty-eight lanthanide coordination polymers (CPs) containing 9,10-anthracene dicarboxylate (ADC) linkers have been synthesized and characterized. For the earlier class of lanthanides La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+ and Tb3+, the 3D pcu net was generated from dimethylformamide (DMF) while a 2D hcb net was formed using dimethylacetamide (DMA). Similarly for the later class of lanthanides, Dy3+, Ho3+, Er3+, Tm3+, Yb3+ and Lu3+, a 2D hcb net was formed when dimethylacetamide (DMA) was used. However, the formation of a crystalline product with DMF was possible only when DMSO was added together for these lanthanides, and they yielded 2D structures despite the usage of DMF. Only the single crystal structures of Er3+ and Ho3+ have been determined and the rest of the structures were confirmed by PXRD studies. These compounds have been used to sense various nitro compounds. In particular, they are the most sensitive to Brady's reagent, 2,4-dinitrohydrazobenzene. There was no difference in the quenching extent between the 3D and 2D early lanthanide CPs. For the later lanthanides which adopt 2D structures, the quenching efficiency is higher when DMA instead of DMSO is coordinated suggesting the solvent effect in emission quenching.

A multifunctional Eu-CP as a recyclable luminescent probe for the highly sensitive detection of Fe3+/Fe2+, Cr2O72-, and nitroaromatic explosives.

A novel 2D lanthanide coordination polymer {Eu-CP (1)} based on a 3-bis(3-carboxyphenyl)imidazolium (L) ligand was successfully assembled through a solvothermal method. Luminescence tests indicate that 1 has excellent selectivity and sensitivity to detect Fe3+/Fe2+, Cr2O72-, and a series of nitroaromatic explosives. Interestingly, 1 can effectively distinguish CrVI anions (CrO42-/Cr2O72-), which is difficult for most of the reported CPs. Furthermore, in the detection process, 1 can be simply and quickly regenerated and reused at least five times. As far as we know, 1 is the first multifunctional Eu-CP used as a luminescent probe to detect Fe3+/Fe2+, Cr2O72-, and a series of nitroaromatic explosives (NAEs) based on the imidazolium derivative.

3D isomorphous lanthanide coordination polymers displaying magnetic refrigeration, slow magnetic relaxation and tunable proton conduction

Four new isostructural lanthanide-based three-dimensional (3D) coordination polymers (CPs), {[Ln4(OH)4(L)2(H2O)8]·4.6H2O·1.4CH3CN}n (Ln3+ = Gd3+ (1), Dy3+ (2), Ho3+ (3) and Er3+ (4)), have been constructed using a sulfonate-carboxylate-based ligand (Na2H2L = disodium-2,2'-disulfonate-4,4'-oxydibenzoic acid) and the corresponding lanthanide metal(iii) nitrates. All the CPs 1-4 contain [Ln4(μ3-OH)4]8+ cubane-like cores interconnected through L4- ligands to give rise to 3D coordination frameworks with 1D hydrophilic channels along the crystallographic c direction. From the topological perspective, the underlying 3D nets of the CPs can be classified as a 3,6,6-c net with an undocumented topology. Magnetic studies display that CP 1 exhibits a magnetocaloric effect with a significant magnetic entropy change (-ΔSm) = 34.6 J kg-1 K-1 for ΔH = 7 T at 3 K. CP 2 shows field-induced slow magnetic relaxation properties with energy barrier (Ueff/kB) = 30.40 K and relaxation time (τ0) = 2.47 × 10-7 s. Theoretical calculations have been performed to corroborate the magnetic exchange coupling constant value for CP 1 and to obtain a deeper understanding of the field-induced slow magnetic relaxation behavior of CP 2. Impedance analyses display high values of proton conductivity which reach 2.02 × 10-6, 2.96 × 10-6, 4.56 × 10-3 and 6.59 × 10-3 S cm-1 for CPs 1-4, respectively at high temperature (>75 °C) and 95% relative humidity (RH) in the order CP 1 < CP 2 < CP 3 < CP 4. Notably, the proton conductivities for CPs 3 and 4 are a few orders of magnitude higher than those of CPs 1 and 2 (10-3 S cm-1vs. 10-6 S cm-1), and the conductivity increases periodically following the decreasing order of ionic radius (Gd3+ > Dy3+ > Ho3+ > Er3+). This demonstrates the effective employment of the lanthanide contraction strategy to tune proton conductivity while preserving proton-conducting pathways.

Rational construction of a porous lanthanide coordination polymer featuring reversible guest-dependent magnetic relaxation behavior

The adjustment of a magnetic relaxation pathway by guest molecules is found in a porous dysprosium complex constructed by hybrid ligands.

Ultrahigh luminescence quantum yield lanthanide coordination polymer as a multifunctional sensor.

The investigation and development of advanced multifunctional and sensitive sensors with high luminescent quantum yield and the capability of detecting different analytes, such as metal ions, is imperative. Due to its inherent properties the lanthanide coordination complex is one candidate for sensing applications, particularly for multifunctional sensors. Herein, we present two series of alkali ion decorated lanthanide coordination polymers (Ln-CPs), which show ultrahigh luminescence quantum yields (QYs) of 77% (1a) and 92% (2a). To the best of our knowledge, 1a represents the first trifunctional lanthanide complex sensor that can simultaneous detect and discriminate three different analytes, namely H+/Cd2+/Cr3+ through a multimode optical response. Furthermore, the limit of detection (LOD) for Cr3+ is an ultralow value of 2.0 × 10-9 M with a sensing time of 2 h, which is comparable to the most sensitive Cr3+ chemosensor. More interestingly, 92% (2a) is an unprecedented luminescence QY among the reported lanthanide coordination complexes.

A series of 3D lanthanide coordination polymers decorated with a rigid 3,5-pyridinedicarboxylic acid linker: syntheses, structural diversity, DFT study, Hirshfeld surface analysis, luminescence and magnetic properties.

Single crystal X-ray diffraction studies reveal the formation of six new coordination polymers (CPs) with the general formulas [Dy(3,5-pdc)(3,5-pdcH)(H2O)2]n·nH2O (1), [Pr2(3,5-pdc)3(H2O)2]n·2n(H2O) (2), [Sm2(3,5-pdc)3(H2O)3]n·nH2O (3), {[Eu2(3,5-pdc)3(H2O)3(CH3CHO)]n·n[2(H2O)(DMF)]} (4), {[Gd2(3,5-pdc)3 (H2O)2]n·2nH2O} (5) and [Er(3,5-pdc)(adip)0.5(H2O)]n (6) (where 3,5-pdc2- = fully deprotonated; 3,5-pdcH- = partially deprotonated 3,5-pyridinedicarboxylic acid; adip2- = fully deprotonated adipic acid; and DMF = dimethylformamide) by solvothermal self-assembly of lanthanide ions with rigid 3,5-pyridinedicarboxylic acid as a linker and adipic acid as an auxiliary flexible spacer (only coordinated in CP 6). CPs 1 and 2 crystallize in the triclinic P1[combining macron] space group, whereas CPs 3, 4 and 6 crystallize in the monoclinic P21/n, P21/c and C2/c space groups, respectively. CP 5 exhibits the trigonal R3 space group. The 3,5-pdc ligand exhibits eight diverse coordination modes in CPs 1-6, whereas the adipic acid spacer in CP 6 shows only one coordination mode (μ4-κO:κO,O:κO:κO,O). The organic ligands interconnect with metal ions to generate 3D metal-organic frameworks with a variety of intriguing topologies. Theoretical studies, DFT calculations and Hirshfeld surface analysis support the structures adopted by the various CPs. CPs 3 (Sm) and 4 (Eu) emit strong ligand-sensitized characteristic f-f luminescence. Weak ferromagnetic interactions have been studied at low temperatures for CP 1 and CP 5.