The lanthanide-containing cyclohexane-tri-carboxylate coordination polymers re-investigated

Reaction in water between trivalent lanthanide ions and ctc³⁻ ligand leads to [Ln(ctc)(H₂O)₂ · 2.5H₂O]_∞ 3-D molecular networks with Ln = Tb-Yb or Y. These compounds look like molecular precursors for porous solids. Unfortunately, the dehydrated phases are not structurally characterized. We report here the study of the partially dehydrated phases with general formula [Ln(ctc)(H₂O)₂]_∞ with Ln = Tb-Yb or Y obtained by freeze-drying of the corresponding hydrated phases. Their porosity is estimated as well as the luminescent properties of the Tb-containing compound.     

Novel 1-D double chain lanthanide complexes: Synthesis, structure and luminescence

Treatment of Ln(NO₃)₃ · 6H₂O with 1, 2-phenylenedioxydiacetic acid (H₂PDOA) in ethanol leads to the unusual 1-D double chain complexes {[Ln(PDOA)_1.5 (H₂O)₃] · H₂O}_n (Ln = Sm (1), Eu (2), Dy (3)), in which the Ln³⁺ ions are linked by pentadentate and bideatate PDOA ligands in two different directions. The chain looks like a ladder containing two -Ln-O-C-O-Ln- chains and PDOA spacers, which has never been observed in the lanthanide carboxylate complexes, and they exhibit different photoluminescence properties.     

Construction of three one-dimensional zinc(II) complexes containing pyrazine-2,3-dicarboxylic acid

Three one-dimensional zinc complexes, namely, [Zn(pzdc) · 3H₂O] · H₂O (1), [Zn₂(pzdc)₂ · 4H₂O] · 2.5H₂O (2), and [Zn(pzdc)(phen) · 4H₂O]_n (3) (H₂pzdc, pyrazine-2,3-dicarboxylic acid, phen = 1,10-phenanthroline), have been synthesized successfully under hydrothermal condition. X-ray diffraction analyses reveal that complex 1 is a square-wave-like chain and complex 2 shows a 1D ladder-like infinite chain, while complex 3 has 1D zigzag chain structure. In all cases, the Zn(II) centers have octahedral coordination geometries. Through hydrogen bonding (such as O-H···O, O-H···N and C-H···O) and/or π-π stacking interactions, three-dimensional supramolecular networks are constructed in three complexes. Furthermore, the IR, TGA and luminescent properties are also investigated in this work.     

New complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) ions with morin

New solid complex compounds of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) ions with morin were synthesized. The molecular formula of the complexes is Ln(C₁₅H₉O₇)₃ · nH₂O, where Ln is the cation of lanthanide and n = 6 for La(III), Sm(III), Gd(III) or n = 8 for Ce(III), Pr(III), Nd(III) and Eu(III). Thermogravimetric studies and the values of dehydration enthalpy indicate that water occurring in the compounds is not present in the inner coordination sphere of the complex. The structure of the complexes was determined on the basis of UV-visible, IR, MS, ¹H NMR and ¹³C NMR analyses. It was found that in binding the lanthanide ions the following groups of morin take part: 3OH and 4CO in the case of complexes of La, Pr, Nd, Sm and Eu, or 5OH and 4CO in the case of complexes of Ce and Gd. The complexes are five- and six-membered chelate compounds.     

Crystal structure and magnetic properties of lanthanide-trans-2-butenoate polymers (Ln = La, Pr, Dy, Ho)

Four lanthanide coordination polymers formulated as {[La₃L₉(H₂O)₃]EtOH · H₂O}_n1, {[Pr₂L₆(H₂O)₂]HL · H₂O}_n2, {[Dy₂L₆(H₂O)]0.5HL · H₂O}_n3 and {[Ho₂L₆(H₂O)]0.5HL · H₂O}_n4 and HL = trans-2-butenoic acid have been synthesized from the corresponding pure lanthanide oxide and HL acid in water at pH 3. The compounds were characterized by chemical analysis, IR spectroscopy, thermogravimetry, variable-temperature magnetic susceptibility and single crystal X-ray diffraction studies. A common feature in these materials is the presence of two differentiated lanthanide nodes linked by carboxylates into extended chains. These are further connected by inter- and intra-molecular hydrogen-bonds involving ligand and solvate molecules. Weak ferromagnetic interactions appear to be operative in the Dy material.     

Structural change of supramolecular coordination polymers of itaconic acid and 1,10-phenanthroline along lanthanide series

Five new supramolecular lanthanide coordination polymers with three different structures, {[La₂(IA)₃(phen)₂] · 2H₂O}_n (1), {[Ln(IA)_1.5(phen)] · xH₂O}_n [x = 1, Ln = Eu (2); x = 0.25, Ln = Dy (3)], and [Ln(IA)_1.5(phen)]_n [Ln = Er (4); Yb (5)], were prepared by hydro- and solvothermal reactions of lanthanide chlorides with itaconic acid (H₂IA) and 1,10-phenanthroline (phen), and structurally characterized by single crystal X-ray diffraction. 1 Comprises 1-D double-chains that are further assembled to a 3-D supramolecular structure via hydrogen bonds and π-π stacks between phen molecules. 2 and 3 have 2-D infinite networks which are further constructed to form 3-D supramolecular architectures with 1-D channels by π-π aromatic interactions. 4 and 5 have 2-D layer structures consisting of three types of rings which are further architectured to form 3-D supramolecular structures by C-H?O hydrogen bonds. The H₂IA ligands are all completely deprotonated and exhibit tetra-, penta-, and hexadentate coordination modes in the titled complexes. The high-resolution emission spectrum of 2 shows only one Eu³⁺ ion site in 2, which is in agreement with the result of X-ray diffraction. And the magnetic property and the thermal stability of 2 were also investigated.     

Hydrolytic stability of SnCl4 and GaCl3 in the formation of [cis-SnCl4(H2O)2] · 18-crown-6 · 2H2O and [[2,2,2]cryptand + 2H][GaCl4]2

The combination of anhydrous SnCl₄ with 18-crown-6 in aqueous conditions results in formation of the non-hydrolysed product [cis-SnCl₄(H₂O)₂] · 18-crown-6 · 2H₂O. The X-ray crystal structure shows extensive intermolecular hydrogen bonding involving the cis-octahedral SnCl₄(H₂O)₂ units, the uncoordinated water molecules and the crown ether. Similarly, [2,2,2]cryptand reacts with an aqueous solution formed by adding anhydrous GaCl₃ to slightly acidic water, affording [[2,2,2]cryptand + 2H⁺][GaCl₄]₂.     

Syntheses, spectroscopic characterization and X-ray structural studies of lanthanide complexes with adamantyl substituted 4-acylpyrazol-5-one

Synthesis and spectroscopic characterization of new lanthanide complexes [Ln(Q_AD)₃(EtOH)(H₂O)], (Ln = Tb, Eu; HQ_AD = 1-phenyl-3-methyl-4-adamantylcarbonyl-pyrazol-5-one), [H₃O][Tb(Q_AD)₄], [Ln(Q_AD)₃(N-N)] (Ln = Tb, Eu; N-N = 1,10-phenanthroline (Phen), 2,2′-bipyridyl (Bipy), 4,4′-dimethyl-2,2′-bipyridyl (4,4′-Me₂Bipy)) are reported. The crystal structures of the proligand HQ_AD and of complexes [H₃O][Tb(Q_AD)₄] and [Tb(Q_AD)₃(4,4′-Me₂Bipy)] have been determined. In both complexes the lanthanide ions are in a square antiprismatic environment, the H₃O⁺ cation in the former acid complex being stabilized by H-bonding. Luminescence studies have been performed on selected derivatives.     

Molecular movements inside [1+1] asymmetric compartmental macrocycles: Formation of positional mononuclear and hetero-dinuclear lanthanide(III) isomers and related homo-dinuclear complexes

The mononuclear macrocyclic lanthanide(III) complexes, [Ln(H₂L)(H₂O)₄]Cl₃ (Ln = Y, La, Ce, Cu, Tb, Yb, Lu; H₂L = H₂L_A, H₂L_B, H₂L_C) were prepared by condensation 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)bis(2-hydroxybenzaldehyde) or 3,3′-(3-oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) with 1,5-diamino-3-azamethylpentane or 1,7-diamino-3-azamethylheptane in the presence of LnCl₃ · nH₂O as templating agent. The asymmetric [1+1] ligands H₂L_A, H₂L_B and H₂L_C contain one smaller or larger N₃O₂ Schiff base site and one crown-ether like O₂O₄ or O₂O₃ site. The preference of the lanthanide ion to reside into the Schiff base or the crown-ether like chamber was investigated in the solid state and in methanol or dimethylsulfoxide solution. It was found that in the solid state or in methanol the lanthanide(III) ion coordinates into the O₂O_n site while in dimethylsulfoxide demetalation and partial metal ion migration from the O₂O_n into the N₃O₂ chamber occur. The mononuclear lanthanide(III) complexes [Ln(H₂L)(H₂O)₄]Cl₃ with the Ln³⁺ ion in the O₂O_n site have been used as ligands in the synthesis of the heterodinuclear complexes LnLn′(L)(Cl)₄ · 4H₂O by reaction with the appropriate Ln′(III) chloride in methanol and in the presence of base. The related homodinuclear complexes Ln₂(L)(Cl)₄ · 4H₂O have been prepared by the one-pot condensation of the appropriate precursors in the presence of base and of the lanthanide(III) ion as templating agent.The single-crystal X-ray structure of [Eu(H₂L_A)(H₂O)₄]Cl₃ · 5H₂O has been determined. The europium ion is nine-coordinated in the O₂O₃ ligand site and bonded to four water molecules and the coordination polyhedron can be described as a square monocapped antiprism.The site occupancy of the different lanthanide(III) ions and the physico-chemical properties arising from the different dinuclear aggregation and/or from the variation of the crown-ether shape have been investigated by IR and NMR spectroscopy, MS spectrometry and SEM-EDS microscopy. In particular, site migration and/or transmetalation reactions, together with demetalation reactions, have been monitored by NMR studies in methanol and dimethylsulfoxide. It was found that these processes strongly depend on the shape of the two coordination chambers, the solvent used and the radius of the lanthanide(III) ions. Thus, these molecular movements can be tuned by changing appropriately these parameters.     

Structure and magnetic properties of Ln2[Cu(opba)]3(DMSO)6(H2O) · (H2O) compounds with LnLa-Lu exhibiting ladder-like molecular motifs

The reaction of Ln(III) ions with the precursor [Cu(opba)]²⁻ in DMSO has afforded a series of isostructural compounds of general chemical formula Ln₂[Cu(opba)]₃(DMSO)₆(H₂O) · (H₂O), where Ln(III) stands for a lanthanide ion and opba stands for ortho-phenylenebis(oxamato). The crystal structure has been solved for the Gd(III) containing compound. It crystallizes in the orthorhombic system, space group Pbn2₁ (No. 33) with a = 9.4183(2) Å, b = 21.2326(4) Å, c = 37.9387(8) Å and Z = 4. The structure consists of ladder-like molecular motifs parallel to each other. To the best of our knowledge, this is the first Ln(III)Cu(II) coordination polymer family exhibiting the same crystal structure over the whole lanthanide series. The magnetic properties of the compounds have been investigated and the magnetic behavior of the Gd(III) containing compound was studied in more detail.     

A family of lanthanide-containing molecular open frameworks with high porosity: [Ln(abdc)(Habdc), nH2O]∞ with Ln = La-Eu and 8 ? n ? 11

Reactions in water between the di-sodium salt of amino terepthalic acid (C₈H₃NO₄Na₂) and a lanthanide chloride lead to a family of 3D-coordination polymers with general chemical formula [Ln(C₈H₃NO₄)(C₈H₄NO₄), O]_∞ where Ln = La-Eu (except Pm) and 8 ? n ? 11. All these compounds are isostructural. High quality single crystals of [Ln(C₈H₃NO₄)(C₈H₄NO₄), nH₂O]_∞ with Ln = La-Sm (except Pm) and 8 ? n ? 11 have been obtained by slow diffusion in agar-agar gels. The crystal structure has been solved for the Nd-containing compound. This compound crystallizes in the cubic system, space group Ia-3 (no. 206) with a = 26.8056(5) Å. The crystal structure can be described as the juxtaposition of large channels with square cross-section.The channels are filled by highly disordered crystallization water molecules. The dehydration of the compounds by freeze-drying is possible and most of the crystallization water molecules can be removed without destruction of the molecular skeleton. The partially dehydrated compounds have general chemical formula [Ln(abdc)(Habdc), 2H₂O]_∞ with Ln = La-Eu except Pm. The porosity of the Nd-containing compound has been estimated by computational methods to 2170 m² g⁻¹. This dehydrated compound reversibly binds water when exposed to wet atmosphere restoring the initial hydrated phase.     

Synthesis and characterization of new lanthanide complexes with hexadentate hydrazonic ligands

In this paper, we report the synthesis and the characterization of a novel series of lanthanide (III) complexes with two potentially hexadentate ligands.The ligands contain a rigid phenanthroline moiety and two flexible hydrazonic arms with different donor atom sets (NNN′N′OO and NNN′N′N″N″, respectively for H₂L¹ (2,9-diformylphenanthroline)bis(benzoyl)hydrazone and H₂L² (2,9-diformylphenanthroline)bis(2-pyridyl)hydrazone).Both nitrate and acetate complexes of H₂L¹ with La, Eu, Gd, and Tb were prepared and fully characterized, and the X-ray crystal structure of the complex [Eu(HL¹)(CH₃ COO)₂] · 5H₂O is presented.The stability constants of the equilibria Ln³⁺ + H₂L¹ = [Ln(H₂L¹)]³⁺ and Ln³⁺ + (L¹)²⁻ = [Ln(L₁)]⁺ (Ln = La(III), Eu(III), Gd(III), and Tb(III)) are determined by UV spectrophotometric titrations in DMSO at t = 25 °C. The nitrate complexes of H₂L² with La, Eu, Gd and Tb were also synthesized, and the X-ray crystal structures of [La(H₂L²)(NO₃)₂(H₂O)](NO₃), [Eu(H₂L²)(NO₃)₂](NO₃) and [Tb(H₂ L²)(NO₃)₂](NO₃) are discussed.     

Gadolinium(III) and europium(III) l-glutamates: Synthesis and characterization

Two lanthanide(III) complexes with l-glutamate ligands [{Ln₂(l-Glu)₂(H₂O)₈} · 4(ClO₄) · 2.5H₂O]_n (Ln = Gd (1), Eu (2)) have been prepared and characterized by single-crystal X-ray diffraction. The compounds are isomorphous with infinite cationic 2D layers stacked together by secondary bonds. The building blocks are slightly different non-centrosymmetric dinuclear units placed in alternating layers, the resulting structures thus containing four non-equivalent Ln metal sites. The dinuclear units contain a fourfold bridge, two in the η¹:η¹:μ₂ and two in the η²:η¹:μ₂ modes, from two α- and two γ-carboxylates of four different l-Glu residues, respectively.     

Lanthanide(III) complexes with phosphoryl containing 1,8-naphthyridine: Crystal structures and vibrational spectra

The complexes of 2-[2-(diphenylphosphoryl)prop-2-yl]-1,8-naphthyridine (L) with lanthanide nitrates Ln(NO₃)₃ (Ln = Nd, Eu, Lu) were investigated to elucidate the coordination ability of a novel type of potentially tridentate ligands - phosphorylalkyl substituted naphthyridines. The X-ray crystal structures of [NdL₃]³⁺ · 3(NO₃)⁻ · MeCN (1), [EuL₃]³⁺ · 3(NO₃)⁻ · [Eu(NO₃)₃ · 4H₂O] · MeCN (2), and [LuL₃]³⁺ · 3(NO₃)⁻ · [Lu(NO₃)₃ · 3H₂O] · 2 MeCN · 0.5 H₂O (3) are reported together with their IR and Raman spectra. All the compounds studied contain isostructural [LnL₃]³⁺ cations and three NO₃⁻ counterions. Coordination of each L appears to be O,N,N tridentate-cyclic and coordination number of Ln is nine. Vibrational spectra of 1-3 are also compared with that of free ligand and model compounds.     

One-dimensional lanthanide coordination polymers as promising luminescent materials

Four one-dimensional coordination polymers, [Ln(H₂O)₄(HTDA)(H₂TDA)] · H₂O [Ln = Sm (1) and Eu (2)]; (H₃TDA = 1H-[1,2,3]-triazole-4,5-dicarboxylic acid), [Ln(H₂O)₄(HTDA)] · (H₂TDA) · H₂O [Ln = Tb (3) and Dy (4)] were prepared and characterized by IR, elemental analysis, PXRD and single-crystal X-ray diffraction. The powder and single-crystal X-ray crystallographic studies of 1-4 reveal that all compounds are one-dimensional zigzag chain structures. Luminescent studies reveal that they are potential luminescent materials. Moreover, in solution, the emission intensity of 2 increases upon the addition of Ca²⁺ ions, while introduction of other metal ions leads to either unchanged or decreased intensity, which indicates that 2 may be applied as a promising Ca²⁺-ion-selective luminescent probe. The basic magnetic properties of 1-4 were also studied.     

Syntheses, crystal structures, and bond valence sum analyses of lanthanide complexes with a planar pentadentate ligand

The syntheses and X-ray crystal structures of the Eu, Gd, Dy, Ho, and Er nitrate complexes of the pentadentate ligand 2,6-diacetylpyridine bis acetic acid hydrazone, or H₂dapaah, are reported. The complexes can be divided into 3 groups depending on the number of water molecules per metal ion. The Ln · 4H₂O complexes with Eu, Gd and Dy are isomorphous, with the Ln ion being 10 coordinate. The Ln · 6H₂O group includes Ho and Er, where the cation is 9 coordinate. The final complex Gd · 5H₂O is 10 coordinate like the Eu, Gd and Dy complexes, but the additional water molecule has stabilized an ordered crystal. The bond valence sum method has been used to analyze the bonding in the complexes and has suggested that bond valence equalization in three dimensions may be an important concept.     

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.     

Diastereoisomerically pure pyrazole-3,5-dicarboxylate-bridged dinuclear ruthenium(II) and osmium(II) complexes of 2,2-bipyridine: structural, electrochemical and spectral studies

Pyrazole-3,5-dicarboxylate-bridged dinuclear ruthenium(II) and osmium(II) complexes of 2,2^′-bipyridine of composition [(bpy)₂Ru(pzdc)Ru(bpy)₂](ClO₄) · H₂O (1) and [(bpy)₂Os(pzdc)Os(bpy)₂](ClO₄) · H₂O (2) have been obtained in high yield and have been separated to their homochiral (ΛΛ/ΔΔ) rac (1a, 2a) and heterochiral (ΛΔ/ΔΛ) meso (1b, 2b) diastereoisomers. The distinctive structural features of these diastereoisomers have been characterized by 1-D and 2-D ¹H NMR spectroscopy. The X-ray crystal structure of rac-[(bpy)₂Os(pzdc)Os(bpy)₂](ClO₄) · H₂O (2a) has been determined. The electrochemical and electronic spectral studies have established that there remain difference in properties and hence difference in intermetallic communication between the diastereoisomeric forms in each case.     

New nine and ten coordinated complexes of lanthanides with bidentate 2-pyrazinecarboxylate containing hydrazinium cation

The new hydrazinium lanthanide metal complexes of 2-pyrazinecarboxylic acid of the formulae (N₂H₅)₂[Ln(pyzCOO)₅] · 2H₂O (1), where Ln = La or Ce and (N₂H₅)₃[Ln(pyzCOO)₄(H₂O)] · 2NO₃ (2), where Ln = Pr, Nd, Sm or Dy have been synthesized by the addition of an aqueous solution of corresponding metal nitrate hydrates to an aqueous mixture of carboxylic acid and hydrazine hydrate in an appropriate ratios. The structure of (N₂H₅)₂[La(pyzCOO)₅] · 2H₂O (1a) and (N₂H₅)₃[Nd(pyzCOO)₄(H₂O)] · 2NO₃ (2a) have been determined from single crystal X-ray analysis. Coordination numbers from six to twelve have been established in lanthanide compounds but ten coordination appears rarely. This work reports the first ten coordinated hydrazinium lanthanide complexes with carboxylate anions. The structure contains lanthanum ions joined by 2-pyrazinecarboxylate groups forming two-dimensional sheets parallel to (0 0 1) plane. 2a is monomeric in nature and the structure comprises of N₂H₅⁺ cations, [Nd(pyzCOO)₄(H₂O)]⁻ and anions. The neodymium is nine coordinated with four pyzCOO lignads, bidentate (N,O) to the metal and the lone water molecule completes the coordination sphere and the sheets like pattern in all are interlinked via multiple hydrogen bonds leading to three dimensional structure.     

Syntheses, structures and photophysical properties of a series of Zn-Ln coordination polymers (Ln = Nd, Pr, Sm, Eu, Tb, Dy)

Six novel heterometallic Zn-Ln coordination polymers {[ZnLnCl(pydc)₂(H₂O)₆]·3H₂O}_n (Ln = Nd 1, Pr 2, Sm 3, Eu 4, Tb 5, Dy 6; pydc = pyridine-2,5-dicarboxylate) were synthesized by the hydrothermal method, and their structures were measured by the single-crystal X-ray diffraction. The IR and UV-Vis-NIR absorption spectra, and the luminescence spectra in the visible and near-infrared (NIR) regions of the six complexes were determined at room temperature. They possess the same crystal structure, and the Zn(II) and Ln(III) ions in each complex are bridged into 1D infinite chain by pyridine-2,5-dicarboxylates. Meanwhile, there are numerous hydrogen bonds which result in the 3D hydrogen bonding network in the crystal. In the visible and NIR regions, the emission spectra of the complexes show the characteristic bands of the corresponding Ln(III) ions, which are mainly attributed to the sensitization from the d-L-moiety to f-L-moiety after forming the Zn-Ln complexes. In this paper, we first report the Zn-Sm complex which can exhibit the emission bands of Sm(III) in the NIR region, and discuss the sensitization from the d-L-moiety to f-L-moiety on the basis of the different characteristics of levels for different Ln(III) ions.