Lanthanide Phosphonates Research Articles

Single-Molecule Magnet Rods: Remarkably Elongated Lanthanide Phosphonate Cores with Quasilinear Hydrazones.

Large metal-phosphonate clusters typically exhibit regular polyhedral, wheel-shaped, spherical, or capsule-shaped morphologies more effectively than high-aspect ratio topologies. A system of elongated lanthanide core topologies has now been synthesized by the reaction of lanthanide 1-naphthylmethylphosphonates and four differently terminated pyrazinyl hydrazones. Four new rod-shaped dysprosium phosphonate clusters, [Dy6(O3PC11H9)4(L1)4(μ4-O)(DMF)4]·2DMF·3MeCN·3H2O (1), [Dy8(O3PC11H9)4(L2)4(μ3-O)4(CO2)4(H2O)4]·6DMF·4MeCN·3H2O (2), [Dy12Na(O3PC11H9)6(L3)6(μ3-O)2(pyr)6]·DMF·2MeCN·H2O (3), and [Dy14(O3PC11H9)12(L4)8(μ3-O)2(DMF)4(MeOH)2(H2O)4]·5DMF·2MeCN·H2O (4), were obtained. Four single-pyrazinyl hydrazones function as pentadentate bis-chelate terminal co-ligands, coordinating the periphery of dysprosium phosphonate rods. A sodium ion serves as a cation template for constructing heterobimetallic 3 by occupying the void, demonstrating the ability to reliably control cluster length by modifying the hydrazone co-ligand structure and cation template. Additionally, it was observed that the elongation of the rods has a significant directional impact on the magnetic relaxation behavior, transitioning from a one-step process in 1 to a three-step process in 2, a two-step process in 3, and finally a two-step process in 4.

Lanthanide Phosphonates and Phosphates in Molecular Magnetism.

Phosphonate and phosphate ligands have historically received less attention when compared to the widely prevalent carboxylate ligand system. Phosphonates possess multiple donating sites, often leading to the formation of larger aggregates with limited solubility. Conversely, the P-O bond within phosphates is highly susceptible to hydrolysis, resulting in the precipitation of insoluble compounds, particularly when interacting with lanthanide metal ions. However, over the past few decades, various synthetic approaches have emerged for the preparation and characterization of lanthanide complexes involving both phosphonate and phosphate ligands. Consequently, researchers have delved into exploring the magnetic properties of these complexes, such as their potential as single molecule magnets (SMMs) and their ability to exhibit a magnetocaloric effect (MCE). This review will encompass an examination of the crystal structures and magnetic characteristics of lanthanide complexes featuring phosphonate and phosphate ligands.

Excitation‐Wavelength‐Dependent Luminescence of Chemically and Physically Mixed Europium and Terbium Phosphonates: Color‐Tunable Luminescence, Near‐White‐Light Emission, and Selective Fe3+ Detection

Molecular lanthanide phosphonates [Ln2 (H3 tpmm)2 (H2 O)6 ] ⋅ xH2 O (Ln=Eu, EuP; Ln=Tb, TbP) were synthesized. Single-crystal X-ray diffraction confirmed that EuP has a sandwich-like dinuclear structure, in which the Eu(III) center adopts a {EuO8 } distorted dodecahedral geometry. XRPD patterns prove that TbP and EuP are isomorphous and isostructural. EuP and TbP are highly thermally stable approaching 450 °C and exhibit red- and green-light emissions from the characteristic 4 f-4 f transition of the Eu3+ and Tb3+ , respectively. Interestingly, luminescence modulation is achieved for the chemically mixed Eu/Tb phosphonate analogues, c-Eux Tb2 -x P (x=1.5, 1, 0.5), and physically mixed Eu/Tb phosphonate materials, p-yEuP : zTbP (y : z=3 : 1, 1 : 1, 1 : 3), with varying the excitation wavelength. Of particular note, near-white-light emission is also achieved for c-EuTbP, p-EuP : TbP, and p-EuP : 3TbP when excited at 365 nm. Therefore, these dinuclear molecular lanthanide phosphonates emitting excitation wavelength and Eu3+ : Tb3+ ratio dependent luminescence might be potential candidates for color-tunable luminescence materials and white-light-emitting materials. On the other hand, the bright green-light emission makes TbP to be an excellent reusable luminescence sensor for selective detection of Fe3+ with Stern-Volmer quenching constant (KSV ) of 9.66×103 M-1 and detection limit (DL) of 0.42 μM through absorption competition caused luminescence quenching effect.

Boosting the proton conduction in a magnetic dysprosium-organic framework by introducing conjugate NH4+-NH3 pairs

Metal-organic frameworks (MOFs) with inherent porosity and suspended acidic groups are promising proton conducting materials in water or aqua-ammonia media. Herein we report a new lanthanide phosphonate, namely, Dy2(amp2H2)2(mal)(H2O)2·5H2O (MDAF-6). It possesses a 3D open-framework structure, and shows a high NH3 adsorption capacity of 142.4 cm3/g at P/P0 = 0.98 at 298 K due to acid-base interaction. Interestingly, the proton conductivity of MDAF-6-NH3 is enhanced by five orders of magnitude compared to MDAF-6 after 8.5 h exposure in saturated NH3-H2O vapor, indicating the importance of coexistent conjugate acid-base pairs of H3O+-H2O and NH4+-NH3 in promoting proton conduction. Magnetic studies of MDAF-6 revealed slow magnetization relaxation under zero dc field, characteristic of single-molecule magnet behavior. This work provides not only a new multifunctional MOF material, but also a new strategy to improve proton conduction in aqua-ammonia medium.

Nanosheets of two-dimensional photoluminescent lanthanide phosphonocarboxylate frameworks decorated with free carboxylic groups for latent fingerprint imaging.

The synthesis, structural characterization, exfoliation, and photophysical studies of two-dimensional (2-D) lanthanide phosphonates, named Ln(m-pbc); [Ln(m-Hpbc)(m-H2pbc)(H2O)] (Ln = Eu, Tb; m-pbc = 3-phosphonobenzoic acid) based on the phosphonocarboxylate ligand, are reported. These compounds are neutral polymeric 2D layered structures with pendent uncoordinated carboxylic groups between layers. The nanosheets were obtained by a top-down strategy involving sonication-assisted solution exfoliation and characterized by atomic force microscopy and transmission electron microscropy, showing lateral dimensions from nano- to micro-meter scales, and thicknesses down to several layers. The photoluminescence studies demonstrate that the m-pbc ligand acts as an efficient antenna toward Eu and Tb(III) ions. The emission intensities of dimetallic compounds are clearly enhanced after incorporation of Y(III) ions due to the dilution effect. Ln(m-pbc)s were then applied for labelling latent fingerprints. It is worth noting that the reaction between active carboxylic groups and fingerprint residues benefits the labelling, showing efficient imaging for fingerprints on all kinds of material surfaces.

Layered lanthanide phosphonates Ln(2-qpH)(SO4)(H2O)2 (Ln = La, Ce, Pr, Nd, Sm): polymorphism and magnetic properties.

Polymorphic layered lanthanide coordination polymers provide opportunities to study the effect of intralayer and interlayer interactions on their magnetic dynamics. Herein we report a series of layered lanthanide phosphonates, namely, α-Ln(2-qpH)(SO4)(H2O)2 (Ln = Sm) (α-Ln), β-Ln(2-qpH)(SO4)(H2O)2 (Ln = Pr, Nd, Sm) (β-Ln) and γ-Ln(2-qpH)(SO4)(H2O)2 (Ln = La, Ce, Pr, Nd, Sm) (γ-Ln) (2-qpH2 = 2-quinolinephosphonic acid), which crystallize in monoclinic P21/c (α-Ln), triclinic P1̄ (β-Ln) and orthorhombic Pbca (γ-Ln) space groups, respectively. The structural differences between the β- and γ-phases lie not only in the intralayer but also in the interlayer. Within the layers, the Ln2O2 dimers are aligned parallel in the β-phase, but are non-parallel in the γ-phase. In the interlayer, there are π-π interactions between the quinoline groups in the α- and β-phases but not in the γ-phase. Magnetic studies reveal a field-induced slow relaxation of the magnetisation at low temperatures for compounds γ-Ce, β-Nd, and γ-Nd, and the impact of polymorphism on the magnetic dynamics of Nd(III) compounds is discussed.

Hybrid Photochromic Lanthanide Phosphonate with Multiple Photoresponsive Functionalities.

Hybrid photochromic materials (HPMs) with specific photoresponsive functionality have applications in many fields. The photoinduced electron-transfer (ET) strategy has been proved to be effective in the synthesis of HPMs with diverse photomodulated properties. The exploitation of new electron acceptors (EAs) is meaningful for promoting the development of HPMs. In this work, we introduced a rigid tetraimidazole derivative, 3,3,5,5-tetra(imidazol-1-yl)-1,1-biphenyl (TIBP) as a potential EA, into a metal-diphosphonate (1-hydroxyethylidene-1,1-diphosphonic acid, H4-HEDP) system to explore HPMs and finally obtained a hybrid metal phosphonate (H4-TIBP)0.5·[Dy(H-HEDP) (H2-HEDP)]·H2O (1). 1 features anionic chains composed of diphosphonate and Dy3+ ions. The extra charge is balanced by protonated TIBP cations, which exist in the void of adjacent chains and form H-bonds with Ophosphonate (N-H···O). Upon photostimulation with a Xe lamp (300 W), the crystalline sample 1 exhibited coloration by changing from colorless to pale yellow because of the presence of photoinduced radicals that originated from the ET from Ophosphonate to NTIBP. Along with the coloration, photomodulated fluorescence, magnetism, and proton conductivity were also detected in the photoactivated samples. Different from the reported HPMs based on polypyridine derivatives and photoactive species such as pyridinium and naphthalimide derivatives as EAs, our study provides a new category of EA units to yield HPMs with fascinating photoresponsive functionality via the assembly of polyimidazole derivatives and phosphonate-based supramolecular building blocks.

Polar Lanthanide Anthracene Complexes Exhibiting Magnetic, Luminescent and Dielectric Properties

AbstractMultifunctional molecular materials combining magnetic, luminescent and dielectric properties are attractive for potential applications in spintronics and molecular devices. Herein we report three isostructural mononuclear lanthanide phosphonates, namely, Ln(NO3)3(2‐deap)3 [Ln=Dy (1Dy), Er (2Er), Yb (3Yb), 2‐deap=diethyl anthrancen‐2‐ylphosphonate] which crystallize in polar space group Pna21. Magnetic studies revealed field‐induced slow magnetization relaxation for 1Dy and 3Yb, but not for 2Er down to 1.8 K. Theoretical calculations were conducted to rationalize the magneto‐structural relationship. The photoluminescent properties are also dependent on the lanthanide ion. For 1Dy, luminescence was observed only in the visible region mainly originating from the ligand. For 2Er, luminescence was observed only in the near‐infrared (NIR) region due to a complete energy transfer from the ligand to the ErIII ion. Regarding to 3Yb, luminescence was observed in both visible and NIR regions suggesting a partial energy transfer from the ligand to YbIII ion. Dielectric and piezoelectric measurements were performed on single crystals of 3Yb, which confirmed the presence of high dielectric anisotropy and weak piezoelectric response.

Multimetal lanthanide phosphonocarboxylate frameworks: structures, colour tuning and near-infrared emission.

A series of isostructural lanthanide phosphonocarboxylate frameworks {(H3O)3[Ln7(pbpdc)6(DMF)4(H2O)3]·4H2O}n (named LnPCF, Ln = Tb, Eu and Gd, H4pbpdc = 4'-phosphono-[1,1'-biphenyl]-3,5-dicarboxylic acid) were solvothermally synthesized and characterized by the single crystal X-ray diffraction technique. By combining lanthanide cations with a phosphonocarboxylate ligand, a heptametallic lanthanide phosphonate [Ln7(PO3)6(COO)12] core was obtained. This core exhibited as a rare highly 18-connected node and was linked by the 3-connected pbpdc4- ligand, forming a (3,18)-connected framework with a novel topology of {43}6{438·676·839}. This LnPCF structure is an ideal platform for accommodating various lanthanide ions. The TbPCF and EuPCF show efficient luminescence emission due to the "antenna effect" and incorporating Gd3+ into the TbPCF results in a drastic luminescence enhancement. Fine colour tuning between green and red can be easily achieved in bimetallic TbxGd1-xPCFs. More significantly, upon combining a few percent of Nd3+ and Gd3+ with Tb3+, the resulting trimetallic Tb0.4Gd0.5Nd0.1PCF shows dual emissions of both visible and near-infrared light.

PH-dependant synthesis, structures and luminescent properties of a series of novel lanthanide phosphonate coordination polymers

A series of two-dimensional layered lanthanide phosphonates, based on 4′-((hydroxy(methoxy)phosphoryl)methyl)-[1,1′-biphenyl]-2-carboxylic acid (H3L′ = HOOC-C6H4-C6H4-CH2-PO(OH)OCH3), Ln(HL)(H2L)(H2O) (H3L = HOOC-C6H4-C6H4-CH2-PO(OH)2), [Ln = La (1), Ce (2), Eu (3), Gd (4), Tb (5), La0.59Eu0.12Tb0.29 (6)] have been obtained by pH-dependent hydrothermal synthesis promoted by ultrasonic. Coordination polymers 1–6 are characterized by single-crystal X-ray diffraction analysis, elemental analysis, infrared spectroscopy, powder X-ray diffraction and thermogravimetry measurements. Their photoluminescence properties are investigated and found that the emission wavelength of 6 could be turned by varying the composition of Ln ions from ligand-centered blue light emission (La3+), to Ln-centered green (Tb3+) and red (Eu3+) light emission, exhibiting white light emission. The magnetic properties of 4 and 5 are also studied.

Reversible SC‐SC Transformation involving [4+4] Cycloaddition of Anthracene: A Single‐Ion to Single‐Molecule Magnet and Yellow‐Green to Blue‐White Emission

AbstractIn search of magneto‐optic materials, the mononuclear compounds LnIII(depma)(NO3)3(hmpa)2 (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo [4+4] dimerization when irradiated at 365 nm without loss of crystallinity. The Dy compound switches from a single‐ion to a single‐molecule magnet with doubling of the spin reversal barrier energy and from yellow‐green to blue‐white emission. The dimerization is reversed by heating at 100 °C or partially on light irradiating at 254 nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto‐optic property.

Reversible SC‐SC Transformation involving [4+4] Cycloaddition of Anthracene: A Single‐Ion to Single‐Molecule Magnet and Yellow‐Green to Blue‐White Emission

In search of magneto-optic materials, the mononuclear compounds LnIII (depma)(NO3 )3 (hmpa)2 (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo [4+4] dimerization when irradiated at 365 nm without loss of crystallinity. The Dy compound switches from a single-ion to a single-molecule magnet with doubling of the spin reversal barrier energy and from yellow-green to blue-white emission. The dimerization is reversed by heating at 100 °C or partially on light irradiating at 254 nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto-optic property.

Rapid and sensitive detection of nitroaromatic explosives by using new 3D lanthanide phosphonates

A terbium phosphonate with its bright green emission, facile synthesis, and low usage can sense nitroaromatic explosives at the ppb scale rapidly.

Syntheses and topological structures of four luminescent lanthanide phosphonates based on 2-(pyridyl-N-oxide)methylphosphonic acid and oxalic acid

To investigate the synthesis and structure of pyridyl-N-oxide phosphonate ligand based lanthanide complexes, a series of four complexes, namely, [NaLn2(pmpa)(C2O4)2.5(H2O)4]·2H2O {Ln=Sm (1), Eu (2), Gd (3), and Tb (4); H2pmpa=2-(pyridyl-N-oxide)methylphosphonic acid; H2C2O4 =oxalic acid}, were hydrothermally synthesized and characterized by elemental analyses, FT-IR, powder and single-crystal X ray diffraction analyses, and thermogravimetric analyses. In the preparation of complexes 1–4, the pH value of reaction system exhibited a significant impact on the product structures. Complexes 1–4, which are isomorphic, exhibited Na ions involving a three-dimensional 4-nodal topological framework with the point symbol of {42·52·62·73·8}{42·5}{43·5·62}{43·5·63·73}. This framework can be further simplified to a 2-nodal topology with the point symbol of {318·436·533·64}{33}2. Photoluminescence studies of complexes 1, 2 and 4 exhibited characteristic luminescence of Sm(III), Eu(III), and Tb(III) ions, while complex 3 exhibited a Gd(III) ions disturbed ligand emissions.

Polymorphic Lanthanide Phosphonates Showing Distinct Magnetic Behavior.

A series of layered lanthanide phosphonates α-Ln(2-qpH)(SO4)(H2O)2 (α-Ln; Ln = Gd, Tb, Ho, Er) and β-Ln(2-qpH)(SO4)(H2O)2 (β-Ln; Ln = Gd, Tb, Ho, Er, Yb) (2-qpH2 = 2-quinolinephosphonic acid) have been synthesized and characterized. Compounds α-Ln crystallize in monoclinic space group P21/c, while compounds β-Ln crystallize in triclinic space group P1̅. Magnetic studies reveal that dominant ferromagnetic interactions are propagated between the magnetic centers in all cases. Field-induced magnetic relaxation is observed in compounds β-Er and β-Yb.

Copper Lanthanide Phosphonate Cages: Highly Symmetric {Cu3Ln9P6} and {Cu6Ln6P6} Clusters with C3v and D3h Symmetry.

Two families of copper lanthanide phosphonate clusters have been obtained through reaction of [Cu2(O2C(t)Bu)4(HO2C(t)Bu)2] and either Ln(NO3)3·nH2O or [Ln2(O2C(t)Bu)6(HO2C(t)Bu)6] and tert-butylphosphonic acid or an amino-functionalized phosphonic acid. The clusters, with general formula [Cu(MeCN)4][Cu3Ln9(μ3-OH)7(O3P(t)Bu)6(O2C(t)Bu)15] and [Cu6Ln6(μ3-OH)6(O3PC(NH2)Me2)6(O2C(t)Bu)12], were structurally characterized through single crystal X-ray diffraction and possess highly symmetric metal cores with approximately C3v and D3h point symmetry, respectively. We have investigated the possible application of the isotropic analogues in magnetic cooling, where we were able to observe that up to around 70% of the theoretical magnetic entropy change is obtained. Simulation of the magnetic data shows antiferromagnetic coupling between the spin centers, which explains the magnetic entropy value observed.

Ordered microporous layered lanthanide 1,3,5-benzenetriphosphonates pillared with cationic organic molecules.

Novel isomorphous pillared-layer-type crystalline lanthanide 1,3,5-benzenetriphosphonates were prepared with bpy and dbo as organic pillars (LnBP-bpy and LnBP-dbo; Ln: Ce, Pr, and Nd). Ab initio crystal structure solution using synchrotron X-ray powder diffraction data revealed that the organic pillars do not exist as neutral coordinating ligands but as cationic molecules. Especially the LnBP-dbo phases have ordered interlayer space filled with water molecules between the dbo pillars, and the interlayer water is successfully removed by heating under vacuum with slightly distorted but basically retained pillared layer structures. Microporosity of the materials is confirmed by adsorption of nitrogen, carbon dioxide, and hydrogen gases. Such microporous layered metal phosphonates pillared with cationic molecules should be unprecedented and should offer new strategies to design ordered microporous materials.

Lanthanide phosphonates with pseudo-D5h local symmetry exhibiting magnetic and luminescence bifunctional properties

Layered lanthanide(iii) phosphonates [Ln(notpH4)(H2O)]ClO4·3H2O [Ln = Dy(1), Ho(2)] in which the lanthanide ion has a pseudo-D5h symmetry show field-induced slow relaxation at low temperatures as well as luminescence properties.

A cryogenic luminescent ratiometric thermometer based on a lanthanide phosphonate dimer

The first example of a ratiometric thermometer based on lanthanide phosphonate is reported, which operates down to the cryogenic temperature range with a maximum relative sensitivity of 3.9% K−1.

Lanthanide diphosphonates based on a V-shaped ligand: syntheses, structures, experimental and theoretical luminescence properties

One series of isostructural lanthanide phosphonates, namely [Ln2(H2L)3][(H2O)5] (H4L = (5-methyl-1,3-phenylene)bis(phosphonic acid); Ln = Eu (1), Gd (2), Tb (3), and Dy (4)), have been successfully synthesized from a V-shaped rigid ligand. Systematic characterizations using single-crystal and powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), and photoluminescence spectroscopy were accomplished. It was found that these compounds all crystallize in the cubic I213 space group, showing three-dimensional framework structures. The frameworks are stable up to 350 °C and show their respective characteristic metal-centered emissions. The photoluminescence properties were also theoretically investigated by using a newly developed software program – LUMPAC. The energy transfer and back energy transfer rates were estimated, and the T1 → 5D1 and T1 → 5D0 channels were revealed to be the dominant pathways. The combination of experimental and theoretical studies on the photoluminescence properties substantially supports the understanding and design of highly luminescent inorganic–organic hybrid materials.