Two Isostructural Layered Lanthanide(III) Complexes: Syntheses,Structures, Magnetic and Luminescent Properties

Two N'-(2-hydroxybenzylidene)pyridine N-oxide-carbohydrazide (H₃L)-based coordination complexes with the formula [Ln₂(DMF)₂(OAc)₂(HL)₂]_n (Ln = Dy for 1 and Eu for 2 ) were solvothermally synthesized. Crystal structures, thermal stabilities, magnetic and luminescent properties of the two complexes were fully investigated. Both complexes are isomorphic two-dimensional layers with centrosymmetric {Ln₂} subunits extended by doubly deprotonated HL^2– connectors. Complex 1 with highly anisotropic Dy^III spin exhibits slightly frequency-dependent magnetic relaxations under zero dc field with an effective energy barrier of ca. 6.84 K. Eu^III-based complex 2 displays only one weak fluorescent emission around 532 nm with the absence of characteristic emission of Eu^III ion. These results provide helpful hints of the hydrazide Schiff-functionalized organic ligands on the function modulations of the resulting Ln complexes.     

Three Phenoxo‐Bridged Dinuclear Lanthanide Complexes: Syntheses,Crystal Structures,and Magnetic Properties

Three dinuclear lanthanide complexes [Ln₂(H₂L)₂(NO₃)₄] [Ln = Dy ( 1 ), Tb ( 2 ), and Gd ( 3 )] [H₃L = 2‐hydroxyimino‐N′‐[(2‐hydroxy‐3‐methoxyphenyl)methylidene]‐propanohydrazone] were solvothermally synthesized by varying differently anisotropic rare earth ions. Single‐crystal structural analyses demonstrate that all the three complexes are crystallographically isostructural with two centrosymmetric Ln^III ions aggregated by a pair of monodeprotonated H₂L^– anions. Weak intramolecular antiferromagnetic interactions with different strength were mediated by a pair of phenoxo bridges due to superexchange and/or single‐ion anisotropy. Additionally, the Dy^III‐based entity shows the strongest anisotropy exhibits field‐induced single‐molecule magnetic behavior with two thermally activated relaxation processes. In contrast, 3 with isotropic Gd^III ion has a significant cryogenic magnetocaloric effect with the maximum entropy change of 25.7 J · kg^–1 · K^–1 at 2.0 K and 70.0 kOe.     

Synthesis,Structure, and Magnetic Properties of a Series of Dinuclear Lanthanide Complexes Assembled by Acetate and a Schiff Base Ligand

Five dinuclear lanthanide complexes [Ln₂L₂(NO₃)₂(OAc)₄] · 2CH₃CN [Ln = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ), and Er ( 5 )] [L = 2‐((2‐pyridinylmethylene)hydrazine)ethanol] were synthesized from the reactions of Ln(NO₃)₃ · 6H₂O with L and CH₃COOH in the presence of triethylamine. Their crystal structures were determined. They show similar dinuclear cores with the two lanthanide ions bridged by four acetate ligands in the μ₂‐η¹:η² and μ₂‐η¹:η¹ bridging modes. Each Ln^III ion in complexes 1 – 5 is further chelated by one L ligand and one nitrate ion, leading to the formation of a nine‐coordinated mono‐capped square antiprism arrangement. The dinuclear molecules in 1 – 5 are consolidated by hydrogen bonds and π ··· π stacking interactions to build a two‐dimensional sheet. Their magnetic properties were investigated. It revealed antiferromagnetic interactions between the Gd^III ions in 1 and ferromagnetic interactions between the Tb^III ions in 2 . The profiles of χ_mT vs. T curves of 3 – 5 reveal that the magnetic properties of 3 – 5 are probably dominated by the thermal depopulation of the Stark sublevels of Ln^III ions.     

Syntheses,Structures, Magnetic Properties,and NIR Emission Properties of a Series of Novel 1, 2, 4, 5‐Cyclohexanetetracarboxylate‐bridged Lanthanide Complexes with 3D Framework Structures

Solvothermal combination of trivalent lanthanide metal precursors with 1, 2, 4, 5‐cyclohexanetetracarboxylic acid (L) ligand has afforded the preparation of a family of eight new coordination polymers [Ln₄(L)₃(H₂O)₁₀] · 7H₂O (Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) ( 1 – 8 ). Structural analyses reveal that the 1, 2, 4, 5‐cyclohexanetetracarboxylic acid ligand with e,a,a,e (L^I) conformation displays a μ₄‐(κ³O, O, O⁵)(κ²O²,O²)(κ²O⁴,O⁴)‐bridging mode to generate 3D frameworks of complexes 1 – 8 and the α‐Po topology with the short Schläfli symbol {4¹².6³} could be observed in complexes 1 – 8 . The near‐infrared luminescence properties were studied, and the results have shown that the Ho^III, Er^III, and Yb^III complexes emit typical near‐infrared luminescence in the solid‐state. Variable‐temperature magnetic susceptibility measurements of complexes 2 – 7 have shown that complex 2 (Gd) shows the ferromagnetic coupling between magnetic centers, whereas the complexes 3 – 7 show the antiferromagnetic coupling between magnetic centers. Additionally, the thermogravimetric analyses were discussed.     

Synthesis,Structures, and Luminescent Properties of Lanthanide Complexes with Triphenylphospine Oxide

Seven lanthanide complexes [Ln(OPPh₃)₃(NO₃)₃] ( 1 – 3 ) (OPPh₃ = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh₃)₄(NO₃)₂](NO₃) ( 4 ), [Ln(OPPh₃)₃(NO₃)₃]₂ ( 5 – 7 ) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh₃ ligand in the air. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1 – 4 are mononuclear complexes formed by OPPh₃ ligands and nitrates. The asymmetric units of complexes 5 – 7 consist of two crystallographic‐separate molecules. Complex 1 is self‐assembled to construct a 2D layer‐structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain‐like structure that was assembled by OPPh₃ ligands and nitrate ions through C–H ··· O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb³⁺ (λ_em = 480, 574 nm) and Eu³⁺ (λ_em = 552, 593, 619, 668 nm).     

Three New Lanthanide Coordination Polymers Built from H2bpdc Ligands: Syntheses,Structures, and Properties

Three new lanthanide‐organic coordination polymers, {[Ln₂(bpdc)₂(H₂O)₆(NO₃)] · NO₃} [Ln = La ( 1 ), Ce ( 2 ), Pr ( 3 )] (H₂bpdc = 2, 2′‐bipyridine‐6, 6′‐dicarboxylic acid) were synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR spectroscopy as well as single‐crystal and powder X‐ray diffraction. Single‐crystal X‐ray diffraction analysis revealed that compounds 1 – 3 are isostructural, composed of two dimensional honeycomb network linked by bpdc ligands. The magnetic property of compound 3 was investigated.     

Synthesis,Crystal Structures,and Magnetic Properties of Two Tetrahedral MnIIMnIII3 Complexes

Two tetranuclear manganese complexes, [NaMn^IIMn₃^III(μ₄‐O^2–)(HL)₃(SCN)₄] ( 1 ) and [NaMn^IIMn₃^III(μ₄‐O^2–)(HL)₃Cl₄][NaMn^IIMn₃^III(μ₄‐O^2–)(HL)₃Cl₃(H₂O)]ClO₄ · 3.5H₂O ( 2 ) were obtained from the reaction of manganese perchlorate with a quadridentate Schiff base ligand, 3‐(2‐hydroxybenzylideneamino)propane‐1, 2‐diol (H₃L) derived from condensation of 2‐hydroxybenzaldehyde with 3‐amino‐1, 2‐propanediol, as well as the coligand KSCN or NaCl under basic conditions. Single‐crystal X‐ray studies reveal that those two complexes all have a mixed‐valent tetrahedral core, which contains an apical Mn^II ion and three basal Mn^III ions situated in the [Mn₃(μ₄‐O^2–)]⁷⁺ equilateral triangle plane. Fitting of the magnetic susceptibility data to the theoretical χ_mT vs. T expression, revealed that the presence of only antiferromagnetic interactions between the central metal atoms in 1 , while both antiferromagnetic and ferromagnetic interactions are present in 2 .     

Synthesis,Structures, and Properties of Lanthanide Complexes with Pyrimidine‐2‐carboxylic Acid

Six lanthanide complexes [Ln(pmc)₂NO₃]_n [Hpmc = pyrimidine‐2‐carboxylic acid, Ln = La ( 1 ), Pr ( 2 )], [Ln(pmc)₂(H₂O)₃]NO₃ · H₂O [Ln = Eu ( 3 ), Tb ( 4 ) Dy ( 5 ), Er ( 6 )] were synthesized by the reactions of lanthanide nitrate and pyrimidine‐2‐carboxylic acid in water at room temperature. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR, circular dichroism (CD) and fluorescence spectra. Structure analysis shows that complexes 1 and 2 are isostructural with P4₃2₁2 space group, whereas isostructural complexes 3 – 6 belong to the P2₁/c space group. In complexes 1 and 2 , the central metal atoms are coordinated by nitrates and pmc^–, which are self‐assembled to construct a 3D porous network with 6₂.6₂.6₂.6₂.6₂.6₂ (6⁶) topology. In complexes 3 – 6 , H₂O and pmc^– ligands are coordinated and the complexes exhibit a one‐dimensional zigzag chain, which is further expanded into a 3D structure by hydrogen bonding. In addition, the circular dichroism of 1 and 2 proves that the two complexes are both chiral with achiral ligand of Hpmc. Luminescent measurements of compounds 3 – 5 indicate that the characteristic fluorescence of Eu³⁺, Tb³⁺, and Dy³⁺ are observed.     

Syntheses,Structures, and Properties of Lanthanide Supramolecular Complexes with 1, 10‐Phenanthroline and Terminal Amino Acids with Different Chain Lengths

Four lanthanide supramolecular coordination compounds, [Eu(gly)₂(phen)₂(H₂O)₂](ClO₄)₃(phen)₄ · H₂O ( 1 ), [Eu₂(APA)₆(phen)₂](ClO₄)₆(phen)₄ · 3H₂O ( 2 ), [Tb₂(ABA)₄(phen)₄](ClO₄)₆(phen)₄ ( 3 ), and [Eu₂(AHA)₄(phen)₄](ClO₄)₆(phen)₂ · 2H₂O · 2C₂H₅OH ( 4 ) (gly = glycine, APA = 3‐aminopropionic acid, ABA = 4‐aminobutanoic acid, AHA = 6‐aminohexanoic acid, phen = 1, 10‐phenanthroline), were synthesized and characterized by single crystal X‐ray diffraction. Compound 1 has a 2‐D supramolecular layered structure of mononuclear coordination cations and free phen molecules connected via hydrogen bonding and π‐π stacking interactions. 2 forms a 3‐D supramolecular network by hydrogen bonding between binuclear coordination cations and free phen molecules, between coordination cations and lattice water molecules, and π‐π stacking interactions between free phen molecules. Compounds 3 and 4 form 2‐D supramolecular structures with π‐π stacking between coordinating phen molecules, and between free phen molecules hydrogen‐bonded to the binuclear coordination cations. The high‐resolution emission spectra show only one Eu³⁺ ion site in the title complexes. The aqueous solutions of the title complexes are all photochromic with the color of the solution changing from yellow to green when irradiated by mercury lamp. During the decoloration process, they return to yellow color.     

Heterometallic Trinuclear Complexes of Macrocyclic Oxamide: Synthesis,Crystal Structures,and Magnetic Properties

Two heterometallic trinuclear complexes of macrocyclic oxamide [Co(Ni L¹ )₂ L² (H₂O)] · 3H₂O ( 1 ) and [Mn(Ni L¹ )₂ L² (H₂O)] · 0.5CH₃OH · 1.5H₂O ( 2 ) (H₂ L¹ = 2,3‐dioxo‐5,6,14,15‐dibenzo‐1,4,8,12‐tetraazacyclopentadeca‐7,13‐diene, H₂ L² = 5‐sulfosalicylic acid) were synthesized and structurally characterized by elemental analysis, IR spectroscopy, and X‐ray diffraction. Single‐crystal X‐ray analyses reveal that both the complexes contain discrete neutral trinuclear [(Ni L¹ )₂M L² (H₂O)] (for 1 and 2 , M = Co, Mn, respectively) moieties. The structures of 1 and 2 have oxamido‐bridged trinuclear [M^IINi^II₂] units and consist of one‐dimensional chains formed by strong intermolecular hydrogen bonds. Furthermore, the magnetic properties of complex 1 were investigated and discussed in detail.     

The Syntheses,Structures, and Magnetic Properties of Four 2D Lanthanide(III)‐naphthalenedicarboxylic Complexes

Four Ln‐NDC coordination polymers [Ln(NDC)(HNDC)(H₂O)] (Ln = La ( 1 ), Pr ( 2 ), Nd ( 3 ), Sm ( 4 ), H₂NDC = 1,4‐naphthalenedicarboxylic acid) were hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single‐crystal X‐ray diffraction. Compounds 1 – 4 are isomorphous, and their structures display a layer constructed from a Ln‐organic chain and NDC^2– ligand, in which the H₂NDC ligands adopt two different acidity‐dependent types and coordination modes: HNDC^1– with μ‐η¹:η¹ and NDC^2– with μ‐η¹:η²:η¹:η². The 3D supramolecular networks of 1 – 4 are mainly controlled by hydrogen bonds interactions. The magnetic susceptibilities of complexes 2 – 4 reveal overall antiferromagnetic interactions between the Ln^III ions. In addition, thermogravimetric analysis of compound 2 is described.     

Syntheses,Structures, and Magnetic Properties of Two DMTCNQ and DETCNQ Gadolinium Complexes

Two DMTCNQ (DMTCNQ = 2,5‐dimethyl‐7,7,8,8‐tetracyano‐p‐quinodimethane) and DETCNQ (DETCNQ = 2,5‐diethyl‐7,7,8,8‐tetracyano‐p‐quinodimethane) gadolinium complexes [Gd(DMTCNQ)₂(CH₃OH)(H₂O)₆][DMTCNQ] · 4H₂O ( 1 ) and [Gd(DETCNQ)(H₂O)₇][2DETCNQ] ( 2 ) were synthesized by reactions of GdCl₃ · 6H₂O with Li(DMTCNQ) or Li(DETCNQ). X‐ray diffraction analysis reveals that complexes 1 and 2 are discrete complexes. The central metal atom in 1 is coordinated by two DMTCNQ ligand radicals whereas that in 2 is coordinated by just one DETCNQ ligand radical. The adjacent molecules are connected by the intermolecular hydrogen bonds to form the two‐dimensional (2D) supramolecular layer structures, which are further packed into a three‐dimensional (3D) supramolecular architecture through the π–π interactions between ligand radicals in 1 and 2 . Magnetic investigation indicates that the antiferromagnetic interactions between spin carriers exists in 1 and 2 .     

Synthesis,Crystal Structures,and Magnetic Properties of Two Copper(II) Radical Heterospin Complexes

Two heterospin complexes [Cu(NIT3Py)(cda)H₂O] · H₂O ( 1 ) and [Cu(NIT2Py)(cda)H₂O] · H₂O · CH₃OH ( 2 ) with Cu^II ions and pyridyl‐substituted nitronyl nitroxide radicals (NITxPy = 2‐(x′‐pyridyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide, x = 3, 2; H₂cda = 4‐hydroxy‐pyridine‐2,6‐dicarboxylic acid) were synthesized and characterized structurally and magnetically. The single crystal structures show that the two complexes are both two‐spin complexes, in which the different radicals make the two complexes have different hydrogen bonding interactions to form 2D and 1D supramolecular network for complexes 1 and 2 , respectively. The magnetic measurements indicate that complexes 1 and 2 both exhibit antiferromagnetic interactions between Cu^II and radicals.     

Syntheses,Structures, Photoluminescence,and Magnetism of a Series of Discrete Lanthanide Complexes based on 2,5‐Dichlorobenzoate and 1,10‐Phenanthroline

The syntheses and crystal structures of eight lanthanide complexes with formula [Ln(2,5‐DCB)_x(phen)_y] are reported, which are characterized via single‐crystal, powder X‐ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis, photoluminescence measurement, and DC/AC magnetic measurement. These eight complexes are isostructural, and possess a discrete dinuclear structure. The adjacent dinuclear molecules are linked by the hydrogen bonding interactions into a one‐dimensional (1D) supramolecular chain. The neighboring 1D chains are further extended into a two‐dimensional (2D) supramolecular layer by the π–π stacking interactions. The photoluminescent properties of complexes 1 (Nd^III), 2 (Sm^III), 3 (Eu^III), 5 (Tb^III), 6 (Dy^III), and 8 (Yb^III) were investigated. Magnetic investigations also reveal the presence of ferromagnetic interactions in complexes 4 (Gd^III), 6 (Dy^III), and 7 (Er^III). Additionally, complex 6 (Dy^III) demonstrates field‐induced slow magnetic relaxation behavior.     

Synthesis,Structures and Magnetic Properties of Cyano‐bridged FeIII/MnIII Heterobimetallic 1D Chain Complexes

Using the tricyanometalate building block, (nBu₄N)[(Tp*)Fe(CN)₃] [Bu₄N⁺ = tetrabutylammonium cation; Tp*^– = hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate], and bidentate Schiff base ligands, HL1 or HL2 {HL1 = 2‐[[(2‐phenylethyl)imino]methyl]phenol; HL2 = 4‐methoxy‐2‐[[(2‐phenylethyl)imino]methyl]phenol}, two heterobimetallic one‐dimensional (1D) chain complexes, [Mn(L1)₂Fe(Tp*)(CN)₃]_n ( 1 ) and [Mn(L2)₂Fe(Tp*)(CN)₃]_n ( 2 ), were synthesized. Single crystal X‐ray diffraction reveal the formation of neutral cyano‐bridged zigzag single chains in 1 and 2 . Magnetic studies demonstrate that both complexes show ferromagnetic interactions between central Fe^III and Mn^III atoms.     

Syntheses,Crystal Structures and Magnetic Properties of Two Lanthanide Mononuclear Complexes

Two isostructural lanthanide complexes, [Tb(salen)_2]_3·3C_2H_9N_2·4CH_4O(1) and [Er(salen)_2]_3·3C_2H_9N_2·2CH_4O(2), where H2 salen = N,N?-bis(3-methoxysalicylidene)ethylene-1,2-diamine, have been in situ synthesized under solvothermal conditions and characterized by IR, elemental analysis, powder and single-crystal X-ray diffraction analysis, and magnetic analysis. Single-crystal X-ray diffraction indicates that the complexes crystallize in monoclinic C121 space group. Each lanthanide center is coordinated with four oxygen and four nitrogen atoms from two salen2-ligands, forming distorted square antiprism geometry. Both 1 and 2 exhibit obvious slow magnetization relaxation under an applied 2 k Oe magnetic field.     

两个双核稀土-自由基化合物的合成、结构及磁性

以乙酰丙酮为共配体的稀土配合物与2-羟基苯取代的自由基配体进行反应得到2个新颖的稀土-自由基配合物[Ln₂（acac）₄（NIT-PhO）₂]（Ln=Tb（1）,Y（2）;acac=乙酰丙酮,NIT-PhOH=2-（2''-hydroxyphenyl）-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide）。2个配合物的结构相同,均是通过2个自由基配体上的羟基氧原子桥联2个稀土离子构成双核结构。直流磁化率的研究表明配合物2具有弱的反铁磁性质。     

Syntheses,Structures, and Properties of Two New Tri‐spin Lanthanide‐Nitronyl Nitroxide (LnIII = GdIII and HoIII) Complexes

Abstract. Two radical–Ln^III–radical complexes, [Ln(hfac)₃(NITPh‐Ph)₂] [Ln = Gd ( 1 ) and Ho ( 2 ), hfac = hexafluoroacetylacetonate; and NITPh‐Ph = 4′‐biphenyl‐4, 4, 5, 5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide] were synthesized and characterized by X‐ray diffraction, elemental analysis, magnetic measurements, as well as IR and UV/Vis spectroscopy. X‐ray crystal structure analysis revealed that the structures of both complexes are isomorphous, the central Ln^III ions are coordinated by six oxygen atoms from three hfac ligand molecules and two oxygen atoms from nitronyl radicals. The temperature dependencies of the magnetic susceptibilities were studied. They showed that in the Gd^III complex, ferromagnetic interactions between Gd^III and the radicals and antiferromagnetic interactions between the radicals coexist in this system (with J_Rad–Gd = 0.1 cm^–1, J_Rad–Rad = –0.309 cm^–1).     

Structure and Magnetic Properties of Two Lanthanide 1,4‐Phenylenediacetate Compounds

The reactions of Ln(NO₃)₃ with 1,4‐phenylenediacetic acid (H₂PDA) under hydrothermal conditions produced two isostructural lanthanide coordination polymers with the empirical formula [Ln₂(PDA)₃(H₂O)] · 2H₂O [Ln = Nd ( 1 ), Sm ( 2 )]. Single‐crystal X‐ray diffraction analyses revealed that both contain one‐dimensionalmetal carboxylato chains, which are further connected by the–CH₂C₆H₄CH₂– spacers of PDA^2– ligands to yield a three‐dimensional metal‐organic framework. Magnetic susceptibilities of 1 and 2 were measured. The experimental χ_mT value of both compounds decreases continuously with decreasing temperature over the whole temperature range. The best least‐squares fit of the experimental data of 1 to a theoretical equation in the temperature range of 70–300 K gives the zero‐field splitting parameter Δ = 2.21 cm^–1 and the magnetic interaction between the Nd^III ions 2zJ′ = –1.97 cm^–1, which indicates the presence of antiferromagnetic interaction between the Nd^III ions. The experimental χ_mT value of 2 at 2 K is much smaller than the expected value for two free Sm^III ions (⁶H_5/2, g = 2/7) in the ground state, indicating that an antiferromagnetic interaction possibly exists between Sm^III ions at low temperature. Fitting the magnetic data of 2 above 110 K based on an equation deduced from the Sm^III ion in a monomeric system with free‐ion approximation gave a spin‐orbit coupling parameter λ = 192(2) cm^–1     

Magnetic and Luminescence Properties of Two Dinuclear Lanthanide Complexes with Butterfly‐like Arrangement

Two dinuclear lanthanide complexes with pentadentate ligand 3‐[bis(pyridine‐2‐ylmethyl)amino]propane‐1,2‐diol (H₂L), formulated as [Ln₂(HL)₂(NO₃)₂(H₂O)₂] · 1.5NO₃ · 0.5I [Ln = Tb ( ZTU‐1 ) and Eu ( ZTU‐2 ); ZTU = Zhaotong University] were synthesized and structurally characterized. ZTU‐1 and ZTU‐2 are isomorphous and feature a butterfly‐like arrangement. The fluorescence properties of ZTU‐1 and ZTU‐2 are investigated and slow magnetic relaxation behavior is observed in ZTU‐1 .