N,N′-Bis(3-methoxysalicylidene)propane-1,2-diamine mononuclear 4f and heterodinuclear Cu-4f complexes: Synthesis, crystal structure and electrochemical properties

Reactions of H₂L [H₂L = N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine] and Ln(NO₃)₃ · 6H₂O give rise to two different mononuclear 4f complexes, namely, {[(H₂L)La(NO₃)₃(MeOH)] · H₂O}_n (1) and [(H₂L)Nd(NO₃)₃] (2). Further additions of Cu(Ac)₂ · H₂O to the mononuclear 4f complexes yield expected heterodinuclear Cu-4f complexes [LCu(Me₂CO)Ln(NO₃)₃] (3, Ln = Nd; 4, Ln = Eu; 5, Ln = Dy). Complex 1 is a unique 1D polymeric chain structure, and 2 is one of the few structurally characterized discrete hexadentate salen-type mononuclear 4f complexes. Complexes 3-5 are similar to their analogues. However, they are prepared by a reversed synthetic route in contrast to their isomorphic complexes. Electrochemical behavior of heterodinuclear Cu-4f complexes 3-5 has been examined by cyclic voltammetry in acetonitrile. The redox potential of heterodinuclear Cu-4f complexes 3-5 shows significant anodic shift comparing to that of mononuclear copper complex (LCu). A tendency of anodic shift was observed in a sequence of 3 < 4 < 5. This results from the modulating effect of coordination geometry around Cu(II) ion on redox potential.     

2D network coordination polymers of lanthanide with N-(2-pyridylmethyl)iminodiacetic acid: Hydrothermal syntheses, crystal structures and luminescent properties

Six lanthanide two-dimensional network coordination polymers with the general formula of [Ln(pmida)(NO₃)(H₂O)]_n, where Ln = La (1), Nd (2), Sm (3), Gd (4), Dy (5), Er (6) and pmida²⁻ = N-(2-pyridylmethyl)iminodiacetate, have been synthesized by hydrothermal process and characterized by elemental analysis, Infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. All crystals are isostructural and crystallize in the monoclinic space group P2₁/a. The lanthanide(III) ion is nine-coordinated in a geometry of distorted tricapped trigonal prism by two N atoms and two O atoms from one pmida²⁻ ligand, two bridging carboxylate O atoms from other two pmida²⁻ ligands, two O atoms of a bidentate chelating nitrate and a O atom of a coordinated water molecule. The luminescent properties of [Sm(pmida)(NO₃)(H₂O)]_n (3) and [Dy(pmida)(NO₃)(H₂O)]_n (5) were investigated.     

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.     

Neutral and cationic rare-earth metal alkyl complexes that contain bis(2-methoxyethyl)(trimethylsilyl)amine, a neutral [ONO]-type ligand

Neutral tris(trimethylsilylmethyl) complexes [Ln(CH₂SiMe₃)₃(L)] (Ln = Sc (1), Lu (2)) and cationic bis(trimethylsilylmethyl) complexes [Ln(CH₂SiMe₃)₂(L)(THF)]⁺[BPh₄]⁻, (Ln = Sc (3), Lu (4)) that contain bis(2-methoxyethyl)(trimethylsilyl)amine (L = Me₃SiN(CH₂CH₂OMe)₂) as a neutral, tridentate ligand were synthesized and characterized by NMR spectroscopy. X-ray structural analysis was performed for the scandium complex 1 and exhibited a distorted octahedral coordination geometry with a facially arranged ligand at the neutral scandium center. NMR spectroscopy corroborated the coordination of the tertiary amine function of the ligand to the metal. Complexes 3 and 4 expand the still limited range of cationic rare-earth metal alkyl complexes with known neutral, multidentate ligands.     

Synthesis and structural characterization of terphenyl based mono(indenide) compounds of the rare-earth elements

The synthesis and X-ray crystal structure determination of the mono(indenide) rare-earth compounds [(DanipO)(Ind)Ln]₂ (Ln = Sm: 1; Ln = Yb: 2) are reported (DanipO = 2-(o-anisyl)-6-(o-2-phenoxide)phenyl, Ind = indenide). Reaction of DanipLi (Danip = 2,6-di-o-anisolphenyl) with the corresponding lanthanide trichloride in tetrahydrofuran followed by addition of two equiv of KInd in tetrahydrofuran at −25 °C yields compounds 1 and 2 in approximately 10-20% yield. The molecular structures of 1 and 2 show an unsolvated dimeric half-sandwich compound and a formally dianionic partially demethylated mixed arylether/aryloxide terphenyl ligand (=DanipO).     

β-Diiminatolanthanoid(III) halides revisited

The crystalline compounds [LnCl₂(L)(thf)₂] [Ln = Ce (1), Tb (2), Yb (3)], [NdI₂(L)(thf)₂] (4), [LnCl(L′)₂] [Ln = Tb (5), Yb (6) (a known compound)] and [YbCl(L′′)(μ-Cl)₂Li(OEt₂)₂] (7) have been prepared [L = {N(C₆H₃Prⁱ₂-2,6)C(H)}₂CPh, L′ = {N(SiMe₃)C(Ph)}₂CH, L′′ = {N(SiMe₃)C(C₆H₄Ph-4)}₂CH]. The X-ray molecular structures of 2-7 have been established; in each, the monoanionic ligand L, L′ or L′′ is N,N′-chelating and essentially π-delocalised. Each of 1-7 was prepared from the appropriate LnCl₃, or for 4 [NdI₃(thf)₂], and an equivalent portion of the appropriate alkali metal [Li for 7, Na for 2, 3 and 5, or K for 1, 4 and 6] β-diiminate in thf; the isolation of exclusively 5 and 6 (rather than the L′ analogues of 2 or 3) is noteworthy, as is the structure of 7 which has no precedent in Group 3 or 4f metal β-diiminato chemistry.     

Efficient synthetic route to anhydrous mononuclear tris(8-quinolinolato)lanthanoid complexes for organic light-emitting devices

A new lanthanoid 8-quinilinolates type structure was found for lanthanum complex La₃(q^Me)₉(H)(NO₃) (1) formed in the reaction of La(NO₃)₃ · 6H₂O with 2-methyl-8-hydroxyquinoline (Hq^Me) and aqueous ammonia in methanol. The molecule of 1 contains three La atoms connected by six bridging quinolinolate ligands, two terminated η²-coordinated q^Me ligands, one terminated η¹-coordinated q^Me ligand and one terminated NO₃ group. The geometry and ¹H NMR spectrum of the complex suggest that it is bearing −1 charge balanced by proton, which was localized objectively. The arrangement of the compound in crystalline state and in pyridine solution is discussed. Syntheses of water- and acid residual-free mononuclear lanthanoid quinolinolates La(q^Me)₃(py)₂ (2) and Lnq₃(py)₂, (Ln = Y (3), La (4), Sm (5), Eu (6), Tb (7), Er (8), Tm (9); q = 8-quinolinolate, py = pyridine) by the reaction of appropriate amido complexes Ln[N(SMe₃)₂]₃ with 3 equiv. of 2-methyl-8-hydroxyquinoline or 8-hydroxyquinoline in pyridine solution is also described. The complex Laq₃(Ph₃PO)₂ (10) was prepared by treatment of 4 with triphenylphosphine oxide in pyridine solution. Lanthanum 2 complex revealed photoluminescence intensity ca. 3 × 10³ times higher than that of the compound 1 prepared by the traditional way in water-alcohol medium. These data give a ground to consider the Lnq₃(py)₂ complexes as promising material for design of light-emitting devices.     

Synthesis, crystal structures and magnetic characterization of heterodinuclear CuGd and CuTb Schiff base complexes

Preparation, crystal structures and magnetic properties of new heterodinuclear Cu^IIGd^III (1) and Cu^IITb^III (2) complexes [CuLn(L)(NO₃)₂(H₂O)₃MeOH]NO₃·MeOH (where Ln = Gd, Tb) with the hexadentate Schiff-base compartmental ligand N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine (H₂L = C₁₉H₂₀N₂O₄Br₂) (0) have been described. Crystal structure analysis of 1 and 2 revealed that they are isostructural and form discrete dinuclear units with dihedral angle between the O1Cu1O2 and O1Gd1/Tb1O2 planes equal to 2.5(1)° and 2.6(1)°, respectively. The variable-temperature and variable-field magnetic measurements indicate that the metal centers in 1 and 2 are ferromagnetically coupled (J = 7.89 cm⁻¹ for 1). Crystal and molecular structure of the Schiff base ligand (0) has been also reported. The complex formation changes the conformation of Schiff base ligand molecule.     

Syntheses, structures, and magnetic properties of 3d-4f heterometallic complexes constructed from pyrazole-bridged CuLn dinuclear units

A series of pyrazole-bridged heterometallic 3d-4f complexes, [CuDy(ipdc)₂(H₂O)₄] · (2H₂O)(H₃O⁺) (1) and [CuLn(pdc)(ipdc)(H₂O)₄] · H₃O⁺ (Ln = Ho (2), Er (3), Yb (4); H₃ipdc = 4-iodo-3,5-pyrazoledicarboxylic acid; H₃pdc = 3,5-pyrazoledicarboxylic acid), {[Cu₃Ln₄(ipdc)₆(H₂O)₁₆] · xH₂O}_n (Ln = Sm (5), x = 8.5; Ln = Eu (6), x = 7; Ln = Gd (7), Tb (8), x = 9), have been synthesized and structurally characterized. Ligand H₃ipdc was in situ obtained by iodination of ligand H₃pdc. Complexes 1-4 are pyrazole-bridged heterometallic dinuclear complexes, and 2-4 are isostructural. Complexes 5-8 are isostructural and comprised of an unusual infinite one-dimensional tape-like chain based on pyrazole-bridged heterometallic dinuclear units. The magnetic properties of compounds 1-4, 7 and 8 have been investigated through the magnetic measurement over the temperature range of 1.8-300 K.     

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.     

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.     

Synthesis, structures and luminescent properties of new heterobimetallic Zn-4f Schiff base complexes

A series of new 3d-4f heterobimetallic Schiff base complexes of the general formula [Zn(μ-L²)Ln(NO₃)₃(H₂O)_n] (Ln = La 1, Nd 2, Gd 3, Er 4 and Yb 5; n = 1 or 2; H₂L² = N,N′-bis(3-methoxy-5-p-tolylsalicylidene)ethylene-1,2-diamine) are synthesized and characterized. Complexes 1, 2, 4 and 5 are structurally characterized by X-ray crystallography. The photophysical properties of these complexes are also investigated. At room temperature, complexes 1-5 exhibit similar solution absorption and emission spectra in the UV-Vis region. Furthermore, compounds 2, 4 and 5 exhibit solution emission corresponding to the lanthanide(III) ion in the near-infrared region at room temperature. The triplet state emission of the 3d-4f bimetallic complexes without energy transfer is also determined through the photophysical study of complex 3.     

Three-dimensional 3d-4f heterometallic polymers containing both azide and carboxylate as co-ligands

The hydrothermal reaction of Ln(NO₃)₃, Ni(NO₃)₂, NaN₃, and isonicotinic acid (L) yielded two novel 3-D coordination frameworks (1 and 2) of general formula [Ni₂Ln(L)₅(N₃)₂ (H₂O)₃] · 2H₂O (Ln = Pr(III) for 1 and Nd(III) for 2), containing Ni-Pr or Ni-Nd hybrid extended three-dimensional networks containing both azido and carboxylate as co-ligands. Both the compounds are found to be isostructural and crystallize in monoclinic system having P2₁/n space group. Here the lanthanide ions are found to be nonacoordinated. Both bidentate and monodentate modes of binding of the carboxylate with the lanthanides have been observed in the above complexes. Variable temperature magnetic studies of the above two complexes have been investigated in the temperature range 2-300 K which showed dominant antiferromagnetic interaction in both the cases and these experimental results are analyzed with the theoretical models.     

Synthesis and luminescent properties of the first series of lanthanide complexes based on sebacate and 2,5-pyridinedicarboxylate

By using 2,5-pyridinedicarboxylate and sebacate as rigid and flexible mixed carboxylate linkers, five new 3D lanthanide complexes, [Ln(seb)_0.5(2,5-pydc)(H₂O)] (Ln = Eu (1), Nd (2), Sm (3), Pr (4) and Tb (5), H₂pydc = 2,5-pyridinedicarboxylic acid, H₂seb = sebacate acid) with macroporous structures, have been synthesized. Complexes 1-5 were characterized by elemental analysis, ICP spectrometer and IR spectroscopy. In particular, the structures of 1-3 were further determined by single-crystal X-ray diffraction. Structural analyses reveal that complexes 1-3 have intricate 3D frameworks, which are constructed by 2,5-pyridinedicarboxylate and sebacate ligands. In addition, the thermogravimetric analysis of 1-3 and photoluminescent properties of 1 and 5 are also discussed in detail.     

Assembly of three novel 2D frameworks with helical chains based on [H2W12O40] clusters and lanthanide - Organic complexes

Three novel polyoxotungstate-based rare earth compounds, [(C₆H₅NO₂)Ln(H₂O)₅]₂[H₂W₁₂O₄₀] · nH₂O (Ln = Ce³⁺ (1), Pr³⁺(2), n = 7; Nd³⁺ (3), n = 6), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra and TG analysis. The structural feature of compounds 1-3 is that the α-metatungstate cluster [H₂W₁₂O₄₀]⁶⁻ anions are linked by the lanthanide (Ln) cation-organic coordination complexes, resulting in a two-dimensional (2D) structure with helical chains. The magnetic properties of compounds 1 and 2 have been studied by measuring their magnetic susceptibility in the temperature range 2-300 K, indicating the existence of spin-orbital coupling interactions and antiferromagnetic response. Furthermore, the electrochemical properties of 1-3 were studied.     

Syntheses and structures of lanthanide complexes containing a bis(imidazolin-2-imino)pyridine pincer ligand

The Lewis acid-base reaction of 2,6-bis[1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine (TL^tBu) and LnCl₃ in THF leads to the corresponding neutral lanthanide complexes of type [(TL^tBu)LnCl₃], Ln = Y (1a), Er (1b), Lu (1c). The yttrium and lutetium complexes have been characterized by X-ray diffraction analysis. The solid state structures reveal that the bulky TL^tBu ligand causes steric crowding around the lanthanide atoms by coordinating to the metal center in a tridentate fashion. In addition, remote C-H?Ln interactions (H?Ln ca. 2.7 Å) involving one of the ^tBu methyl groups are observed in both cases. A DFT (density functional theory) calculation on 1a was able to reproduce this interaction, which was additionally characterized by means of an H?Y compliance constant and by employing the AIM (atoms in molecules) theory.     

Supramolecular isomers of lanthanides(III): Synthesis, crystal structures and luminescent properties

Six lanthanide coordination polymers La₂(1,4-BDOA)₂(OX)(H₂O) (1), Ln₂(1,4-BDOA)₂(OX)(H₂O) [Ln = La (2); Ln = Pr (3); Ln = Sm (4); Ln = Eu (5); Ln = Tb (6)], [BDOA = benzene-1,4-dioxydiacetate; OX = oxalate] had been prepared under hydrothermal conditions, which were characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Compounds 1-6 crystallize in a triclinic system, space group ; compounds 1 and 2 are true structural supramolecular isomers based on BDOA ligands constructed from different acid effects; compounds 2-5 are isostructural and exhibit new 3D 12-connected topological networks, which are the same as the topological structure of 6, while 1 shows another 3D 11-connected topological architecture. Furthermore, the luminescent properties of 5 and 6 were studied.     

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.     

A series of pyrazolone lanthanide (III) complexes: Synthesis, crystal structures and fluorescence

A series of pyrazolone lanthanide complexes: Ln(PMPP)₃ · 2H₂O · C₂H₅OH (Ln = Nd (1), Sm (2), Gd (3), Dy (4); PMPP = 1-phenyl-3-methyl-4-propionyl-5-pyrazolone) have been synthesized by the hydrothermal method with the starting ligand PMPP-SAH (1-phenyl-3-methyl-4-(salicylidene hydrazone)-propionyl-5-pyrazolone) changed into PMPP during the formation process of complexes. All the complexes were structurally characterized by X-ray crystallography. The fluorescence of these four complexes 1-4 in solid state and DMF solution was investigated via F-4500 spectrophotometer and all of them indicate a fluorescent behavior at room temperature.     

Nature of the Ln-Co magnetic interactions in compounds [Ln2Co3(C5H4NPO3)6] · 4H2O with open-framework structures

The reactions of Ln(NO₃)₃ · xH₂O, CoSO₄ · 7H₂O or ZnSO₄ · 6H₂O and 2-pyridylphosphonic acid under hydrothermal conditions result in heterometallic phosphonate compounds with formula [Ln₂M₃(C₅H₄NPO₃)₆] · 4H₂O (Ln₂M₃; M = Co^II or Zn^II; Ln = La^III, Ce^III, Pr^III, Nd^III, Sm^III, Eu^III, Gd^III, Tb^III, Dy^III). These compounds are isostructural and crystallize in a chiral cubic space group I2₁3. Each structure contains the {LnO₉} polyhedra and {MN₂O₄} octahedra which are connected by edge-sharing to form an inorganic open-framework structure with a 3-connected 10-gon (10, 3) topology. The nature of Ln^III-Co^II magnetic interactions in Ln₂Co₃ is investigated by a comparison with their Ln^III-Zn^II analogues. It is found that the Ln^III-Co^II interaction is weak antiferromagnetic for Ln = Ce and ferromagnetic for Ln = Sm, Gd, Tb and Dy. In the cases of Ln = Pr, Nd and Eu, no significant magnetic interaction is observed.