Lanthanide Contraction Effect Research Articles

Ternary complexes of neodymium(III) and samarium(III) picrate triethylene glycol: structural, spectroscopic, and photoluminescent properties

The ternary complexation of neodymium(III) and samarium(III) with triethylene glycol (EO3) and picrate anion (Pic) were characterized by elemental analyses, FTIR (Fourier-transform infrared) spectroscopy, single crystal X-ray diffraction, and photoluminescence (PL). Both the [Nd(Pic)(H2O)2(NO3)(EO3)](Pic) and [Sm(Pic)(H2O)2(NO3)(EO3)](Pic)·H2O complexes were isostructural with a ten-coordination number. In both complexes, the picrate and nitrate anions were coordinated to Ln(III) in a bidentate manner, and with the the EO3 ligand in a tetradentate manner, the addition of two water molecules maintained a ten-coordination number. The lighter lanthanide-picrate complexes formed a ten-coordination number due to the lanthanide contraction effect, acyclic polyether chain length, and number of donor oxygen atoms. The acyclic EO3 ligand affected photoluminescent intensity and its conformation on the structure of the [Ln(Pic)(NO3)(H2O)2(EO3)]+ moiety. Photoluminescent measurement showed complex Nd(III) emissions at 403, 486, and 682 nm, with the strongest emission peak at 403 nm. Formation of these peaks occurred due to the intraligand π–π transitions of the Pic anion. The Sm(III) complex exhibited the emission characteristic of the Sm(III) ion in the red spectral region at 616.7 nm (4G5/2 → 6H9/2 transition), even though the ligand emissions were also observed in the PL spectrum. The emission intensity of the 4f–4f transitions in the Sm complex was significantly higher than that found in its salt. We noted that the [Sm(Pic)(H2O)2(NO3)(EO3)](Pic)·H2O complex was an excellent red-light-emitter and would be considered as a candidate material for organic light emitting diodes.

New class of Preyssler-lanthanide complexes with modified and extended structures tuned by the lanthanide contraction effect

A family of polyoxometalate compounds based on Preyssler anions and lanthanide cations, K(5)Na(5)[{Pr(4)(H(2)O)(12)(pydc)(4)}{Na(H(2)O)P(5)W(30)O(110)}]·46H(2)O (1, H(2)pydc = pyridine-2,6-dicarboxylic acid), Na(7)[{Pr(4)(H(2)O)(20)(pydc)(2)(Ac)}{Na(H(2)O)P(5)W(30)O(110)}]·23H(2)O (2), and Na(10)H(2) [{Ln(2)(H(2)O)(10)(pydc)(2)}{Na(H(2)O)P(5)W(30)O(110)}]·XH(2)O (Ln = Sm 3, Eu 4, Gd 5; X = 11 for 3 and 5, 13 for 4), have been synthesized and characterized by elemental analysis and single crystal X-ray diffraction. Compound 1 exhibits a two-dimensional honeycomb layer which is built up from unique {Pr(4)} metallacycles and Preyssler anions. Remarkably, the strong involvement of the sodium countercations leads to the formation of a unique three-dimensional open architecture with one-dimensional channels. The 2D grid layer of compound 2 is constructed by the longest currently known rare-earth metal clusters {Pr(8)} and Preyssler anions. Isostructural compounds 3, 4, and 5, obtained by introduction of the intermediate lanthanide ions into the above reaction system, exhibit bisupporting [{Ln(2)(H(2)O)(10)(pydc)(2)}{Na(H(2)O)P(5)W(30)O(110)}](12-) polyoxometalate cluster structures. The magnetic properties of compounds 1 and 2 and the luminescent properties of compounds 3 and 4 are discussed in this paper.

Solvothermal syntheses and characterizations of lanthanide(iii)/SbS43− complexes associated by a dien ligand: A detailed study based on the lanthanide contraction effect

Neutral lanthanide thioantimonate complexes with the formula [Ln(dien)2(μ-η1, η2-SbS4)]n (Ln1) (Ln = Pr 1a, Nd 1b, Sm 1c) and [Ln(dien)2(η2-SbS4)] (Ln2) (Ln = Eu 2a, Dy 2b) have been synthesized by the solvothermal reaction of antimony and sulfur powders with the corresponding lanthanide oxide in diethylenetriamine (dien). In 1a–1c, the tetrathioantimonate SbS43− anion acts as a μ-η1, η2-SbS4 tridentate bridging ligand to interlink [Ln(dien)2]3+ ions into neutral 1D coordination polymers [Ln(dien)2(μ-η1, η2-SbS4)]n, but it coordinates to the Ln3+ ions of [Ln(dien)2]3+ in 2a and 2b as a η2-SbS4 bidentate chelating ligand, leading to neutral complexes [Ln(dien)2(η2-SbS4)]. The Ln3+ ions are in 9-fold and 8-fold coordinations in Ln1 and Ln2 respectively. A systematic investigation of the crystal structures of five complexes as well as two reported compounds revealed that the soft Lewis basic ligand SbS43− coordinates to the larger lanthanide ions La3+, Ce3+, Pr3+, Nd3+, and Sm3+ as a μ-η1, η2-SbS4 tridentate bridging ligand, and to the smaller lanthanide ions Eu3+ and Dy3+ as a η2-SbS4 bidentate chelating ligand, which exhibits a lanthanide contraction effect on the coordination mode of the SbS43− ligand to the Ln3+ centers.

Diverse lanthanide coordination polymers tuned by the flexibility of ligands and the lanthanide contraction effect: syntheses, structures and luminescence

Two new flexible exo-bidentate ligands were designed and synthesized, incorporating different backbone chain lengths bearing two salicylamide arms, namely 2,2'-(2,2'-oxybis(ethane-2,1-diyl)bis(oxy))bis(N-benzylbenzamide) (L(I)) and 2,2'-(2,2'-(ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl))bis(oxy)bis(N-benzylbenzamide) (L(II)). These two structurally related ligands are used as building blocks for constructing diverse lanthanide polymers with luminescent properties. Among two series of lanthanide nitrate complexes which have been characterized by elemental analysis, TGA analysis, X-ray powder diffraction, and IR spectroscopy, ten new coordination polymers have been determined using X-ray diffraction analysis. All the coordination polymers exhibit the same metal-to-ligand molar ratio of 2 : 3. L(I), as a bridging ligand, reacts with lanthanide nitrates forming two different types of 2D coordination complexes: herringbone framework {[Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)](∞) (Ln = La (1), and Pr (2), m = 1, 2)} as type I,; and honeycomb framework {[Ln(2)(NO(3))(6)(L(I))(3)·nCH(3)OH](∞) (Ln = Nd (3), Eu (4), Tb (5), and Er (6), n = 0 or 3)} as type II, which change according to the decrease in radius of the lanthanide. For L(II), two distinct structure types of 1D ladder-like coordination complexes were formed with decreasing lanthanide radii: [Ln(2)(NO(3))(6)(L(II))(3)·2C(4)H(8)O(2)](∞) (Ln = La (7), Pr (8), Nd (9)) as type III, [Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)·nCH(3)OH](∞) (Ln = Eu (10), Tb (11), and Er (12), m, n = 2 or 0) as type IV. The progressive structural variation from the 2D supramolecular framework to 1D ladder-like frameworks is attributed to the varying chain length of the backbone group in the flexible ligands. The photophysical properties of trivalent Sm, Eu, Tb, and Dy complexes at room temperature were also investigated in detail.

A series of new rare earth sulfates based on lanthanide contraction and dual organic-amine templating effects

Five different types of dual organic-amine templated lanthanide sulfates, [(CH3)2NH2]6[H3N(CH2)2NH3][Nd2(SO4)7] (1), [(CH3)2NH2]3[Eu(SO4)3] (2), [(CH3)2NH2]2[H3N(CH2)2NH3]0.5[Ln(SO4)3] (3) (LnEu (3a), Gd (3b), Tb (3c)), [(CH3)2NH2]4[Dy2(SO4)5] (4) and [H3N(CH2)2NH3]5[Ln2(SO4)8] (5) (LnDy (5a), Ho (5b), Er (5c), Tm (5d), Yb (5e), Lu (5f)) have been solvothermally obtained by employing dimethylacetamide (DMAc) as solvent and characterized by single-crystal X-ray diffraction, IR spectroscopy, thermal analysis, fluorescent spectra and ICP. The zigzag chain structure of compound 1 is constructed from two types of 4-membered rings (4 MRs) which connect each other alternately by sulfate groups. The one-dimensional (1D) chainlike structure of compound 2 is alternately linked by tetramer [Eu2(SO4)2O10] and 4 MR units. Compounds 3a to 3c are isomorphous and have similar interesting two-dimensional (2D) frameworks fabricated through zigzag chains and 12 MRs, fully protonated ethylenediamine (en) are located in 12 MRs and protonated dimethylamine (dma) are located between the inorganic layers. Compound 4 exhibits a 2D layered structure and the plane layers consist of two types of double stranded chains and 12 MRs. Compounds 5a to 5f are also isomorphous and feature a binuclear lanthanide cluster structure. Although the 12 compounds were synthesized under the same conditions except the rare earth oxide types, they belong to five types of structures and we can clearly see obvious transitivity and uniformity, as the ionic radius decreases, the coordination number of the rare earth elements decreases from 9 to 8 and the lanthanide contraction supports crystal structures concerning a sterically hindered coordination atmosphere. The luminescent properties of compounds 2, 3a and 3c exhibit characteristic europium and terbium luminescence.

Coordination complexes based on pentacyclohexanocucurbit[5]uril and lanthanide(iii) ions: lanthanide contraction effect induced structural variation

Eight coordination complexes, {LnCl2(H2O)3Q*[5]}·NO3·18.5H2O [isomorphous for Ln = La (1), Ce (2) and Pr (3)], {LnCl2(H2O)2Q*[5]}·NO3·14H2O [isomorphous for Ln = Nd (4) and Sm (5)], {Dy(H2O)2[Cl ⊂ Q*[5]]Dy(H2O)6}·5Cl·20H2O (6), {LnCl(H2O)[Cl ⊂ Q*[5]]Ln(H2O)6}·4Cl·13H2O [isomorphous for Ln = Ho (7) and Er (8)], were obtained by reactions of the corresponding lanthanide species with the macrocyclic ligand pentacyclohexanocucurbit[5]uril (Q*[5]) in aqueous solution, and their structures were determined by single-crystal X-ray diffraction. Crystal structure analysis reveals that, in complexes 1–5, each Q*[5] coordinates to one lanthanide(III) ion to form an opened molecular capsule structure, and then adjacent molecular capsules bridge each other to form a 1-D coordination polymer structure, while in complexes 6–8, each Q*[5] coordinates to two lanthanide(III) ions to form a 0-D half-opened molecular capsule structure. These complexes show that their structural variations are ascribed to the effect of lanthanide contraction.

Guided ion beam and theoretical study of the reactions of Os+ with H2, D2, and HD

Reactions of the third-row transition metal cation Os(+) with H(2), D(2), and HD to form OsH(+) (OsD(+)) were studied using a guided ion beam tandem mass spectrometer. A flow tube ion source produces Os(+) in its (6)D (6s(1)5d(6)) electronic ground state level. Corresponding state-specific reaction cross sections are obtained. The kinetic energy dependences of the cross sections for the endothermic formation of OsH(+) and OsD(+) are analyzed to give a 0 K bond dissociation energy of D(0)(Os(+)-H) = 2.45 ± 0.10 eV. Quantum chemical calculations are performed here at several levels of theory, with B3LYP approaches generally overestimating the experimental bond energy whereas results obtained using BHLYP and CCSD(T), coupled-cluster with single, double, and perturbative triple excitations, levels show good agreement. Theory also provides the electronic structures of these species and the potential energy surfaces for reaction. Results from the reactions with HD provide insight into the reaction mechanism and indicate that Os(+) reacts via a direct reaction. We also compare this third-row transition metal system with the first-row and second-row congeners, Fe(+) and Ru(+), and find that Os(+) reacts more efficiently with dihydrogen, forming a stronger M(+)-H bond. These differences can be attributed to the lanthanide contraction and relativistic effects.

Hydrothermal synthesis, crystal structure, and photoluminescence of novel lanthanide metal organic frameworks constructed from 1,4-benzene-dicarboxylic acid and 1,2,4,5-benzenetetracarboxylic acid as ligands

By using 1,4-benzene-dicarboxylic acid and 1,2,4,5-benzenetetracarboxylic acid as mixed-linkers, three novel 3D lanthanide coordination polymers, [Ln(BDC)0.5(BTEC)0.5(H2O)] (Ln = Eu (1) and Gd (2)) and [Tb(BDC)0.5(BTEC)0.5(H2O)] (3) (H2BDC = 1,4-benzene-dicarboxylic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid) were synthesized via hydrothermal reaction. The X-ray single crystal analyses reveal that the three coordination polymers present two types of different crystal cell parameters and hereby exhibited two kinds of different metal–organic frameworks, although they have the similar chemical formula [Ln(BDC)0.5(BTEC)0.5(H2O)]. Of these complexes, complexes 1 and 2 are isomorphous, crystallizing in monoclinic, space group P21/n. While 3 is a 3D eight-coordinated terbium complex with triclinic crystal system and P-1 space group. The occurrence of the different structures of these complexes under the similar preparation method may be related to the lanthanide contraction effect. Additional, the thermogravimetric analyses and photoluminescent properties for complexes 1 and 3 were discussed in detail. Three novel coordination polymers, [Ln(BDC)0.5(BTEC)0.5(H2O)] (Ln = Eu (1) and Gd (2)) and [Tb(BDC)0.5(BTEC)0.5(H2O)] (3) (H2BDC = 1,4-benzene-dicarboxylic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid) have been firstly synthesized hydrothermally. Complexes 1 and 2 are isomorphous, crystallizing in monoclinic, space group P21/n. While 3 is a novel eight-coordinated Tb(III) complex with triclinic crystal system and P-1 space group.

Two- to One-Dimensional: Radii-Dependent Self-Assembly Crystal Structures and Luminescent Properties of Lanthanide Coordination Polymers with an Amide Type Semirigid Bridging Ligand

Lanthanide coordination polymers {[Ln2L3(NO3)6]·nH2O}n [Ln = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7), and Er (8), where n = 0 except for 1 with n = 4 and 2 with n = 7] have been assembled using lanthanide nitrates and an amide type semirigid bridging ligand, 1,3-bis{[(2′-benzylaminoformyl)phenoxyl]methylbenzene (L), as building blocks. The crystal structures of the complexes {[Pr2L3(NO3)6]n·4H2O}n (1), {[Nd2L3(NO3)6]·7H2O}n (2), [Sm2L3(NO3)6]n (3), [Eu2L3(NO3)6]n (4), [Tb2L3(NO3)6]n (6), and [Er2L3(NO3)6]n (8)} were determined by single-crystal X-ray diffraction. Interestedly, 1 and 2 demonstrate unusual lanthanide porous noninterpenetrated honeycomb-like (6,3) topology frameworks, while 3, 4, 6, and 8 exhibit novel one-dimensional linear coordination polymeric structures. Their structural variations are attributed to lanthanide contraction effects. The luminescent properties of Sm(III), Eu(III), Tb(III), and Dy(III) complexes are also investigated in detail. The lowest triplet state (T1) energy level of this ligand matches better to the lowest resonance energy levels of Tb(III) and Dy(III) than Eu(III) and Sm(III) ions.

Lanthanide(III)/Pyrimidine-4,6-dicarboxylate/Oxalate Extended Frameworks: A Detailed Study Based on the Lanthanide Contraction and Temperature Effects

Detailed structural, magnetic, and luminescence studies of six different crystalline phases obtained in the lanthanide/pyrimidine-4,6-dicarboxylate/oxalate system have been afforded: {[Ln(μ-pmdc)(μ-ox)(0.5)(H(2)O)(2)]·3H(2)O}(n) (1-Ln), {[Ln(μ-pmdc)(μ-ox)(0.5)(H(2)O)(3)]·2H(2)O}(n) (2-Ln), {[Ln(μ(3)-pmdc)(μ-ox)(0.5)(H(2)O)(2)]·~2.33H(2)O}(n) (3-Ln), {[Ln(2)(μ(3)-pmdc)(μ(4)-pmdc)(μ-ox)(H(2)O)(3)]·5H(2)O}(n) (4-Ln), {[Ln(μ(3)-pmdc)(μ-ox)(0.5)(H(2)O)(2)]·H(2)O}(n) (5-Ln), and [Ln(pmdc)(1.5)(H(2)O)(2.5)] (6-Ln). The slow generation of the oxalate (ox) anion, obtained from the in situ partial hydrothermal decomposition of the pyrimidine-4,6-dicarboxylate (pmdc) ligand, allows us to obtain good shaped single crystals, while direct addition of potassium oxalate provides the same compounds but as polycrystalline samples. The crystal structures of all compounds are based on the double chelation established by the pmdc and ox ligands to provide distorted 2D honeycomb layers that, in some cases, are fused together, leading to 3D systems, by replacing some of the coordinated water molecules that complete the coordination sphere of the lanthanide by uncoordinated carboxylate oxygen atoms of the pmdc. The presence of channels occupied by crystallization water molecules is also a common feature with the exception of compounds 5-Ln. It is worth noting that compounds 3-Ln present a commensurate crystal structure related to the partial occupancy of the crystallization water molecules placed within the channels. Topological analyses have been carried out, showing a previously nonregistered topology for compounds 4-Ln, named as jcr1. The crystal structures are strongly dependent on the lanthanide ion size and the temperature employed during the hydrothermal synthesis. The lanthanide contraction favors crystal structures involving sterically less hindranced coordination environments for the final members of the lanthanide series. Additionally, reinforcement of the entropic effects at high temperatures directs the crystallization process toward less hydrated crystal structures. The magnetic data of these compounds indicate that the exchange coupling between the lanthanide atoms is almost negligible, so the magnetic behavior is dominated by the spin-orbit coupling and the ligand field perturbation. The luminescence properties that exhibit the compounds containing Nd(III), Eu(III), and Tb(III) have been also characterized.

Effect of Lanthanide Contraction on Crystal Structures of Three-Dimensional Lanthanide Based Metal–Organic Frameworks with Thiophene-2,5-Dicarboxylate and Oxalate

Six three-dimensional (3D) lanthanide coordination polymers with formula [Ln(TDC)(ox)0.5(H2O)2]·(H2O) (1Ln) (Ln = Pr 1, Nd 2, Sm 3, Gd 4) and [Ln(TDC)(ox)0.5(H2O)2]·(H2O) (2Ln) (Ln = Dy 5, Er 6) have been synthesized by hydrothermal reactions of thiophene-2,5-dicarboxylate (TDC) and oxalate (ox) with corresponding lanthanide nitrate. X-ray crystal structure analyses reveal that 1Ln and 2Ln are isomers that may be produced by lanthanide contraction. Compounds 1–4 are isostructural and possess binodal (4,5)-connected 3D framework of tcj/hc topology with triangular channels along the [101] direction. Isostructural compounds 5 and 6 present trinodal (4,4,6)-connected 3D framework of sqc254 topology with rectangular channels along the b axis. The magnetic properties reveal that compound 2 has antiferromagnetic behavior, while compound 4 has ferromagnetic behavior. The luminescent property shows that compound 5 displays intense yellow luminescence and exhibits the typical Dy3+ ion emission. Furthermore, infrare...

Guided ion beam and theoretical study of the reactions of Au+ with H2, D2, and HD

Reactions of the late third-row transition metal cation Au(+) with H(2), D(2), and HD are examined using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au(+) in its (1)S (5d(10)) electronic ground state level. Corresponding state-specific reaction cross sections for forming AuH(+) and AuD(+) as a function of kinetic energy are obtained and analyzed to give a 0 K bond dissociation energy of D(0)(Au(+)-H) = 2.13 ± 0.11 eV. Quantum chemical calculations at the B3LYP∕HW+∕6-311+G(3p) and B3LYP∕Def2TZVPP levels performed here show good agreement with the experimental bond energy. Theory also provides the electronic structures of these species and the reactive potential energy surfaces. We also compare this third-row transition metal system with previous results for analogous reactions of the first-row and second-row congeners, Cu(+) and Ag(+). We find that Au(+) has a stronger M(+)-H bond, which can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals. Results from reactions with HD provide insight into the reaction mechanism and indicate that ground state Au(+) reacts largely via a direct mechanism, in concordance with the behavior of the lighter group 11 metal ions, but includes more statistical behavior than these metals as well.

Photoluminescent and Magnetic Properties of a Series of Lanthanide Coordination Polymers with 1H-Tetrazolate-5-formic Acid

Reaction of lanthanide oxides and 1H-tetrazolate-5-ethyl formate in water at 50 °C in the presence of pyridine afforded a series of lanthanide coordination polymers, {(Hpy)2[Pr4(tzf)7(H2O)11]·10H2O}n (1) and {[Ln2(tzf)3(H2O)6]·4H2O}n, where Ln = Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Hpy = protonated pyridine, and H2tzf = 1H-tetrazolate-5-formate acid. Polymer 1 features a three-dimensional (3-D) anion framework built up by cross-linkage of tetrameric [Pr4(tzf)4]4+ units and tzf2− ligands, showing a six-connected primitive cubic (pcu) topology (412·63). Isomorphous polymers 2−6 present a two-dimensional (2-D) neutral structure with a four-connected (4,4) topology. Four new coordination modes of the tzf2− ligand are first observed in tetrazolate-5-carboxylate complexes. The lanthanide contraction effect and coordination flexibility of tzf2− ligand play a key role in governing the formation of coordination polymers with different polymeric architectures. The photoluminescent analyses for 2, 3, 5, and 6 suggest that ligand-to-Ln(III) energy transfer is efficient, especially for Eu(III) and Tb(III) ions, and the tzf2− ligand may act as a good “antenna molecule” to sensitize Ln(III) emission. The variable-temperature magnetic study shows that magnetic interactions between the Ln(III) ions in 1−6 are mainly ascribed to the antiferromagnetic coupling as well as the depopulation of the Stark levels. The spin−orbit coupling parameters (λ) for Sm(III) in 2 and Eu(III) in 3 are 259(2) and 344(1) cm−1, respectively, based on the free-ion approximation.

Effect of lanthanide contraction and rigid ligand on the structure of salen-type lanthanide complexes

Three types of phenolate oxygen-bridged N,N′-bis(2-oxy-3-methoxybenzylidene)-1,2-diaminophenylene 3d–4f heteronuclear and 4f tetranuclear complexes, namely, [(LZnCl)PrCl2(CH3OH)2]2 (1), [(LZnCl)LnCl(OAc)(CH3OH)] (Ln = Tb (2) and Dy (3)) and [{(LLu2)(OAc)2(H2O)(OH)}2(ZnCl4)]·2H2O (4) are obtained by reactions of H2L (H2L = N,N′-bis(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine), LnCl3·6H2O (Ln = Pr, Tb, Dy and Lu) and Zn(OAc)2·2H2O in CH3OH/CH2Cl2. X-Ray crystallographic analysis reveals that complex 4 possesses a novel defect-dicubane core, where four Lu3+ ions are inserted into the two sets of N2O2 and O2O2 cavities among the two tail-to-tail ligands. The structural investigations unambiguously testify that the lanthanide contraction and the rigid ligand cooperatively affect the formation of complexes 1–4, where Ln3+ ions with large, medium and small radius are composed in three different structures. The fluorescent spectrum of complex 2 exhibits the characteristic metal-centred fluorescence of Tb3+ ions.

A series of di-, tri- and tetranuclear lanthanide clusters with slow magnetic relaxation for Dy2 and Dy4

A series of dinuclear, trinuclear and tetranuclear lanthanide complexes, formulated as [Nd2(Acc)6(H2O)4]3 [Nd2(Acc)6(H2O)6]·Cl24·8H2O (1), [Dy2(Acc)4(H2O)8]·Cl6·5.89H2O (2), [Ln3(Acc)10(H2O)6]·(ClO4)9·4H2O (Ln = La, (3); Nd, (4)) and [Ln4(μ3-OH)4(Acc)6(H2O)7(ClO4)] ·(ClO4)7·11H2O (Ln = Dy, (5); Yb, (6)), have been synthesized through the reaction of 1-amino cyclohexanel-carboxylic acid (Acc) and LnCl3/Ln(ClO4)3. Crystal structure analysis reveals that complexes 1 and 2 show dinuclear lanthanide cluster, complexes 3 and 4 have three lanthanide ions with a linear arrangement, while complexes 5 and 6 exhibit a cubane-like [Ln4(μ3-OH)4]8+ (Ln = Dy and Yb) cluster core. Their structural variations are attributed to the effect of anions and lanthanide contraction. Magnetic studies indicate that the Dy2 and Dy4 clusters exhibit slow relaxation of magnetization.

Unusual (4,6)-connected lanthanide 1,3-phenylenediacetate coordination frameworks displaying lanthanide contraction effect and 1D and 2D mixed self-weaving architecture

A series of 2D Ln-organic coordination frameworks (Ln = Sm3+ for 1, Eu3+ for 2, Tb3+ for 3, and Ho3+ for 4) with (4,6)-connected (44.52)(44.5.6)(44.54.66.7) topology has been constructed, in which 1D zigzag chains and 2D (4,4) networks intertwine mutually into the unusual 1D and 2D mixed self-weaving patterns. Interestingly, due to the lanthanide contraction effect, the 9-coordinated geometries of the Ln(III) ions gradually transform from triangle tetrakaidecahedron (Sm3+ and Eu3+), to a three-capped triangle prism (Eu3+ and Tb3+), and then to a single-capped anti-square prism (Ho3+).

Lanthanide Contraction and Temperature-Dependent Structures of Lanthanide Coordination Polymers with Imidazole-4,5-Dicarboxylate and Oxalate

Three series of two-dimensional (2D) lanthanide coordination polymers of [Ln(HIDC)(OX)0.5(H2O)2]n·(H2O)n (1Ln) (Ln = Pr and Nd), [Ln(HIDC)(OX)0.5(H2O)2]n·(H2O)n (2Ln) (Ln = Eu and Tb), and [Ln(HIDC)(OX)0.5(H2O)]n (3Ln) (Ln = Pr, Nd, Eu, and Tb) have been prepared by reacting Ln(NO3)3·6H2O with imidazole-4,5-dicarboxylic acid (H3IDC) and oxalic acid (H2OX) at different temperatures under hydrothermal conditions. The results of structural analyses indicate that 1Ln and 2Ln are supramolecular isomers, in which 1Ln displays a 2D monolayer structure of [Ln(HIDC)(OX)0.5(H2O)2]n with a (4.52)(4.53.72) topology network, while 2Ln shows a different 2D monolayer structure containing alternating one-dimensional (1D) left-handed and right-handed helical chains of [Ln(HIDC)]∞ bridged by OX2−. 3Ln has a 2D double-layer structure consisting of oxalate pillared [Ln(HIDC)(H2O)]nn+ layers. The effect of lanthanide contraction and of temperature on the structures of 1Ln-3Ln was investigated. The structure related luminescen...

Anion-Exchangeable Layered Materials Based on Rare-Earth Phosphors: Unique Combination of Rare-Earth Host and Exchangeable Anions

Layered materials, three-dimensional crystals built from stacking two-dimensional components, are attracting intense interest because of their structural anisotropy and the fascinating properties that result. However, the range of such layered materials that can exchange anions is quite small. Continuing efforts have been underway to identify a new class of anion-exchangeable materials. One major goal is the incorporation of rare-earth elements within the host because researchers expect that the marriage of rare-earth skeleton host and the exchangeable species within the interlayer will open up new avenues both for the assembly of layered materials and for the understanding of rare-earth element chemistry. Such lanthanide layered solids have industrial potential. These materials are also of academic importance, serving as an ideal model for studying the cationic size effect on structure stability associated with lanthanide contraction. In this Account, we present the work done by ourselves and others on this novel class of materials. We examine the following four subtopics regarding these layered anionic materials: (1) synthesis strategy and composition diversity, (2) structural features, (3) structure stability with relative humidity, and (4) applications. These materials can be synthesized either by hydrothermal reactions or by homogeneous precipitation, and a variety of anions can be intercalated into the gallery. Although only cations with a suitable size can form the layered structure, the possible range is wide, from early to late lanthanides. We illustrate the effect of lanthanide contraction on properties including morphology, lattice dimensions, and coordination numbers. Because each lanthanide metal ion coordinates water molecules, and the water molecules point directly into the gallery space, this feature plays a critical role in stabilizing the layered structure. In the 9-fold monocapped square antiprism structure, the humidity-triggered transition between high- and low-hydrated phases corresponds to the uptake of H(2)O molecules at the capping site, which provides further evidence of the importance of water coordination. Applications using this unique combination of rare-earth element chemistry and layered materials include ion-exchange, photoluminescence, catalysis, and biomedical devices. Further exploration of the compounds and new methods for functional modification would dramatically enrich the junction of these two fields, leading to a new generation of layered materials with desirable properties.

Rare earth element release from phosphate minerals in the presence of organic acids

The primary objective of this research was to investigate the effects of aliphatic and aromatic low molecular weight organic acids (LMWOAs) on rare earth element and yttrium (REY) release from the phosphate minerals apatite and monazite. Since prior studies have shown that redox status can affect REY partitioning during incongruent dissolution, a secondary objective was to assess the influence of dissolved O 2 concentration. Increasing LMWOA concentrations from 0 to 10 mM resulted in enhanced REY release. In general, REY release increased in the order: no ligand ≈ salicylate < phthalate ≈ oxalate < citrate. REY–ligand stability constants were only useful for predicting REY release for oxalate reacted with apatite and phthalate reacted with monazite. The role of dissolved oxygen in dissolution of the phosphate minerals was mixed and inconsistent. Mineral type was observed to significantly affect REY pattern development. REY release patterns for apatite range from nearly flat to those exhibiting the lanthanide contraction effect (radius-dependent fractionation); whereas, monazite REY release patterns are best described as exhibiting an M-type lanthanide tetrad effect (radius-independent fractionation). Weathering of apatite in the presence of aliphatic LMWOAs resulted in development of the lanthanide contraction effect fractionation pattern, and the aliphatic LMWOAs further developed MREE and radius-independent fractionation during monazite dissolution. Geochemical and mineral-specific REY signatures may, therefore, have utility for distinguishing the impacts of biota on soil weathering processes on early Earth. The development of such signatures may be mitigated, in part, by accessory mineral composition, the types and concentration of LMWOAs present, and precipitation of secondary minerals.

Rare-earth organic frameworks involving three types of architecture tuned by the lanthanide contraction effect: hydrothermal syntheses, structures and luminescence

The first example of rare-earth organic frameworks with 3-aminopyrazine-2-carboxylic acid (Hapca) was synthesized under hydrothermal conditions and characterized by elemental analysis, IR, PL, TG, powder and single-crystal X-ray diffraction. These ten complexes exhibit three different structure types with decreasing lanthanide radii: [La(apca)(3)](n) () for type I, {[Ln(apca)(ox)(H(2)O)(2)].H(2)O}(n) (Ln = Pr (2), Nd (3), ox = oxalate) for type II, and [Ln(2)(apca)(4)(OH)(2)(H(2)O)(2)](n) (Ln = Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Er (9), Y (10)) for type III. The structure of type I consists of 1D "snowflake" chains along a-axis, which are further interconnected by hydrogen bonds to produce a 3D sra net topology containing infinite (-C-O-La-)(n) rod-shaped SBU. Type II has 2D Ln-apca-ox 4(4)-net, in which a planar udud water tetramers (H(2)O)(4) are formed by coordinated and free water molecules. Type III also comprises of 2D 4(4)-layer network constructed from Ln-apca-OH. The structure diversity is mainly caused by the variation of coordinated ligand and lanthanide contraction effect. Remarkably, the oxalate in type II was in situ synthesized from 3-aminopyrazine-2-carboxylic acid through an oxidation-hydrolysis reaction. The luminescent investigations reveal that complex exhibits strong blue emission and complex exhibits characteristic luminescence of Eu(3+).