镧系水合离子的密度泛函理论研究

用密度泛函理论(DFT)方法研究了镧系水合离子[Ln(H2O9)]^3+(Ln=Ce,Pr,Nd,Pm,Ho,Er,Tm,Yb)的几何构型、电荷分布和Ln^3+与水的结合能,计算结果与实验基本符合,表明DFT方法也适用于计算镧系离子与中性配体形成的化合物,对计算结果的分析表明,Ln^3+与H2O之间主要通过Ln5d轨道与氧孤对电子相互作用成键而结合,其余轨道起的作用比较小,用镧系化合物成键模型解释了镧系离子与水的结合能从La到Lu逐渐增加的事实。     

Periodic trends in lanthanide and actinide phosphonates: discontinuity between plutonium and americium

The hydrothermal reactions of trivalent lanthanide and actinide chlorides with 1,2-methylenediphosphonic acid (C1P2) in the presence of NaOH or NaNO(3) result in the crystallization of three structure types: RE[CH(2)(PO(3)H(0.5))(2)] (RE = La, Ce, Pr, Nd, Sm; Pu) (A type), NaRE(H(2)O)[CH(2)(PO(3))(2)] (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy; Am) (B type), or NaLn[CH(2)(PO(3)H(0.5))(2)]·(H(2)O) (Ln = Yb and Lu) (C type). These crystals were analyzed using single crystal X-ray diffraction, and the structures were used directly for detailed bonding calculations. These phases form three-dimensional frameworks. In both A and B, the metal centers are found in REO(8) polyhedra as parts of edge-sharing chains or edge-sharing dimers, respectively. Polyhedron shape calculations reveal that A favors a D(2d) dodecahedron while B adopts a C(2v) geometry. In C, Yb and Lu only form isolated MO(6) octahedra. Such differences in terms of structure topology and coordination geometry are discussed in detail to reveal periodic deviations between the lanthanide and actinide series. Absorption spectra for the Pu(III) and Am(III) compounds are also reported. Electronic structure calculations with multireference methods, CASSCF, and density functional theory, DFT, reveal localization of the An 5f orbitals, but natural bond orbital and natural population analyses at the DFT level illustrate unique occupancy of the An 6d orbitals, as well as larger occupancy of the Pu 5f orbitals compared to the Am 5f orbitals.     

镧系元素4f轨道在成键中的作用的理论研究

用密度泛函方法在冻结或不冻结4f轨道的条件下计算一系列含镧系元素双原子 分子,对结果进行分析,得出以下结论：镧系元素4f轨道按传统的化学键理论观点 是不直接参与成键的,但对成键有一定作用：通过与匹配物的轨道混合使键长变短 ,键能增加,一般可达百分之几。随着镧系原子序数的增加4f轨道对成键的贡献减 少。电负性高或价态高的匹配物对4f轨道的作用较强,4f轨道对成键的影响比较大 。对于重镧系元素,匹配物不是F或O时,4f轨道对成键的贡献相当小,可以看成芯 轨道,但对于轻稀土,在比较精确的计算中则应作为价轨道处理。镧系元素与氟结 合时,只有对靠近Yb的重镧系元素才可以把4f当作芯轨道,而与氧结合时即使对于 YbO把Yb4f作为芯轨道仍会带来较大误差。     

某些镧系化合物化学键特性的INDO研究

本文用INDO方法研究了不同价态镧系化合物的成键性质和4f轨道在成键中的作用,结果表明, 镧系化合物的成键受许多因素, 如价态、半径、配位数、空间构型等影响。不同配体与镧系元素成键的强度差别较大; 高价态的共价性大于低价态的; 配位数低的大于配位数高的。某些特殊构型的镧系化合物除σ键外, 还形成重叠较好的π配键,使Ln-L键共价性大大增强。4f轨道在成键中的作用比5d的少得多, 三价(二价态)的4f轨道基本定域(<0.1%), 四价态的4f轨道对成键的贡献明显增大, 可接近1%。     

High efficiency co-sensitized solar cell based on luminescent lanthanide complexes with pyridine-2,6-dicarboxylic acid ligands

Two lanthanide complexes, Ln(HPDA)(3)·4EtOH (Ln = Tb, Dy) (H(2)PDA = pyridine-2,6-dicarboxylic acid, EtOH = ethanol), have been successfully synthesized using hydrothermal or solvothermal methods, and their crystal structures were analyzed by single crystal XRD. Both crystals have orthorhombic symmetry with space group Pbcn, exhibiting three-dimensional (3D) supramolecular architecture through hydrogen bonding interactions. The metal center was coordinated to nine atoms by three pyridine-2,6-dicarboxylic acid ligands. The nine-coordinated lanthanide metal complexes were assembled onto a nanocrystalline TiO(2) film to form co-sensitized photoelectrodes with N719 for dye-sensitized solar cells, and their photoelectrochemical performance was studied. In the tandem structure of composite electrodes, the energy levels of lanthanide metal complexes are reorganized in their single-crystal form, as verified by ab initio calculations. The co-sensitized systems are far superior for electron-injection and hole-recovery compared with single N719-sensitized systems. Luminescence properties were measured and electrochemical analysis was also performed on these complexes.     

Direct solvothermal growth, crystal structures, and optical properties of one-dimensional lanthanide selenidoarsenate(v) polymers [Ln(dien)2(micro3-AsSe4)] (Ln = Nd, Sm): the first example of an AsSe4(3-) anion acting as a ligand to a lanthanide complex

Two novel lanthanide selenidoarsenates(v) [Ln(dien)2(micro(3)-AsSe(4))] (Ln = Nd 1, Sm 2, dien = diethylenetriamine) were synthesized by the reactions of As(2)O(3) and Se with Nd(2)O(3) or Sm(2)O(3) in dien under solvothermal conditions. 1 and 2 are in the orthorhombic crystal system with Iba2 and Pbca space groups, respectively. The [AsSe(4)](3-) anion acts as a tridentate micro(3)-AsSe(4) ligand to bridge the lanthanide [Ln(dien)2](3+) complexes leading to one-dimensional neutral [Ln(dien)(2)(micro(3)-AsSe(4))](infinity) chains. The chains contact through hydrogen bonding to form network structures. The lanthanide center lies within a nine-coordinated environment involving six N atoms of two dien ligands and three Se atoms of two different tetrahedral [AsSe(4)](3-) anions forming a distorted monocapped square antiprism. The novel coordination polymers [Nd(dien)2(micro(3)-AsSe(4))](infinity) and [Sm(dien)2(micro(3)-AsSe(4))](infinity) are the first examples of solvothermally synthesized selenidoarsenates with [AsSe(4)](3-) anion acting as a ligand in lanthanide complexes. The band gaps of 2.11 eV for 1, and 2.18 eV for 2 have been derived from optical absorption spectra. TG-DSC curves show that two compounds remove coordinated dien ligands in a single step.     

Experimental and theoretical comparison of actinide and lanthanide bonding in M[N(EPR(2))(2)](3) complexes (M = U, Pu, La, Ce; E = S, Se, Te; R = Ph, iPr, H)

Treatment of M[N(SiMe3)2]3 (M = U, Pu (An); La, Ce (Ln)) with NH(EPPh2)2 and NH(EPiPr2)2 (E = S, Se), afforded the neutral complexes M[N(EPR2)2]3 (R = Ph, iPr). Tellurium donor complexes were synthesized by treatment of MI3(sol)4 (M = U, Pu; sol = py and M = La, Ce; sol = thf) with Na(tmeda)[N(TePiPr2)2]. The complexes have been structurally and spectroscopically characterized with concomitant computational modeling through density functional theory (DFT) calculations. The An-E bond lengths are shorter than the Ln-E bond lengths for metal ions of similar ionic radii, consistent with an increase in covalent interactions in the actinide bonding relative to the lanthanide bonding. In addition, the magnitude of the differences in the bonding is slightly greater with increasing softness of the chalcogen donor atom. The DFT calculations for the model systems correlate well with experimentally determined metrical parameters. They indicate that the enhanced covalency in the M-E bond as group 16 is descended arises mostly from increased metal d-orbital participation. Conversely, an increase in f-orbital participation is responsible for the enhancement of covalency in An-E bonds compared to Ln-E bonds. The fundamental and practical importance of such studies of the role of the valence d and f orbitals in the bonding of the f elements is emphasized.     

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.     

Sandwich-type tetranuclear lanthanide complexes with cucurbit[6]uril: from molecular compounds to coordination polymers

Sandwich-type lanthanide complexes with macrocyclic ligand cucurbit[6]uril (C 36H 36N 24O 12, CB[6]) were synthesized under hydrothermal conditions from aqueous solutions of lanthanide(III) bromides, CB[6], and 4-cyanopyridine. According to X-ray analysis (Ln = La, Pr, Dy, Ho, Er, and Yb), the compounds with different structural types of lanthanide cores have a common fragment where the tetranuclear hydroxo complex is sandwiched between two macrocycles {(IN@CB[6])Ln 4(mu 3-OH) 4(IN@CB[6])} (6+) (IN = isonicotinate). The photoluminescence (for Ln = Eu) and Fourier transform ion cyclotron resonance mass spectra (for Ln = Pr, Dy, and Er) were studied. The compounds are used for the first time as precursors for the synthesis of lanthanide-silver heterometallic coordination polymers. The chainlike crystal structure of polymers (Ln = La, Pr, and Dy) is constituted by the sandwich complexes linked via the coordination of IN nitrogen atoms to the silver atoms.     

4f fine‐structure levels as the dominant error in the electronic structures of binary lanthanide oxides

The ground‐state 4f fine‐structure levels in the intrinsic optical transition gaps between the 2p and 5d orbitals of lanthanide sesquioxides (Ln₂O₃, Ln = La…Lu) were calculated by a two‐way crossover search for the U parameters for DFT + U calculations. The original 4f‐shell potential perturbation in the linear response method were reformulated within the constraint volume of the given solids. The band structures were also calculated. This method yields nearly constant optical transition gaps between Ln‐5d and O‐2p orbitals, with magnitudes of 5.3 to 5.5 eV. This result verifies that the error in the band structure calculations for Ln₂O₃ is dominated by the inaccuracies in the predicted 4f levels in the 2p‐5d transition gaps, which strongly and non‐linearly depend on the on‐site Hubbard U. The relationship between the 4f occupancies and Hubbard U is non‐monotonic and is entirely different from that for materials with 3d or 4d orbitals, such as transition metal oxides. This new linear response DFT + U method can provide a simpler understanding of the electronic structure of Ln₂O₃ and enables a quick examination of the electronic structures of lanthanide solids before hybrid functional or GW calculations. © 2015 Wiley Periodicals, Inc.     

Solid-state and solution structure of lanthanide complexes of a new nonadentate tripodal ligand containing phenanthroline binding units

The new nonadentate tripodal ligand trenphen (tris[(1,10-phenanthroline-2-carboxamido)-ethyl]amine) has been synthesized by condensation of tren [tris(2-aminoethyl)amine] with an excess of 1,10-phenanthroline-2-carboxylic acyl chloride. The ligand trenphen and its lanthanide complexes (Sm, Nd, Eu, Tb, and Lu) have been structurally characterized by single-crystal X-ray diffractometry. Crystals of trenphen.H2O.CH3CN, 1, are monoclinic, space group P2(1)/n, a = 14.9923(8) A, b = 17.4451(10) A, c = 17.1880(10) A, beta = 114.8290(10) degrees, V = 4079.9(4) A3, Z = 4. The solid-state crystal structures of the isostructural [Ln(trenphen)](OTf)3.yH2O.xEt2O.zCH3CN (OTf = CF3SO3) (Ln = Nd, y = 0.5, x = 1, z = 3 (2); Ln = Sm, y = 0.5, x = 1, z = 3 (3); Ln = Eu, y = 0.5, z = 3 (4); Ln = Tb, y = 0.5, x = 1, z = 1.5 (5); Ln = Lu, y = 0.5, x = 1, z = 1.5 (6)) (trigonal, P-3, Z = 2) show that the covalent tripod trenphen undergoes a rearrangement in the presence of lanthanide ions yielding three tridentate binding units which encapsulate the nine-coordinated lanthanide ion with a slightly distorted, tricapped, trigonal prismatic coordination geometry. The correlation observed between the decrease of Ln-N distances and the metal ionic radius indicates that trenphen, although containing rigid bidentate phenanthroline units, is sufficiently flexible to self-organize without steric constraints around lanthanide ions of different size. Solution-state NMR studies show that complexes 2-6 exist in acetonitrile solution as discrete rigid C3-symmetric species retaining the triple-helical structure observed in the solid state. NMR and ES-MS titration show the formation of bimetallic and trimetallic species in the presence of an excess of metal, whereas mononuclear bistrenphen complexes are obtained in the presence of an excess of ligand.     

Coordination of lanthanide triflates and perchlorates with N,N,N',N'-tetramethylsuccinamide

Compounds formed from the reaction of N,N,N',N'-tetramethylsuccinamide (TMSA) with trivalent lanthanide salts possessing the poorly coordinating counteranions triflate (CF3SO3-) and perchlorate (ClO4-) have been prepared and examined. Structural features of these Ln-TMSA compounds have been studied in the solid phase by thermogravimetric analysis, infrared spectroscopy, and, in selected cases, by single-crystal X-ray diffraction and in solution by infrared spectroscopy. Eight-coordinate compounds, [Ln(TMSA)4]3+, derived from coordination of four succinamide ligands to the metal ion could be formed with all lanthanides examined (Ln = La, Pr, Nd, Eu, Yb, Lu). Structural analyses by single-crystal X-ray diffraction were performed for the lanthanide triflate salts Ln(C8H16N2O2)4(CF3SO3)3: Ln = La, compound 1, monoclinic, P2(1)/n, a = 11.0952(2) A, b = 19.2672(2) A, c = 24.9759(3) A, beta = 90.637(1) degrees, Z = 4, Dcalcd = 1.586 g cm-3; Ln = Nd, compound 2, monoclinic, C2/c, a = 24.6586(10) A, b = 19.3078(7) A, c = 11.1429(4) A, beta = 90.450(1) degrees, Z = 4, Dcalcd = 1.603 g cm-3; Ln = Eu, compound 3, monoclinic, C2/c, a = 24.4934(2) A, b = 19.3702(1) A, c = 11.1542(1) A, beta = 90.229(1) degrees, Z = 4, Dcalcd = 1.617 g cm-3; Ln = Lu, compound 5, monoclinic, C2/c, a = 24.2435(4) A, b = 19.6141(2) A, c = 11.2635(1) A, beta = 90.049(1) degrees, Z = 4, Dcalcd = 1.626 g cm-3. X-ray analysis was also carried out for the perchlorate salt: Ln = Eu, compound 4, triclinic, P1, a = 10.9611(2) A, b = 14.6144(3) A, c = 15.7992(2) A, alpha = 106.594(1) degrees, beta = 91.538(1) degrees, gamma = 90.311(1) degrees, Z = 2, Dcalcd = 1.561 g cm-3. In the presence of significant amounts of water, 7-coordinate compounds with mixed aquo-TMSA cation structures [Ln(TMSA)3(H2O)]3+ (Ln = Yb) and [Ln(TMSA)2(H2O)3]3+ (Ln = La, Pr, Nd, Eu, Yb) have been isolated with structural determinations by single-crystal X-ray diffraction obtained for the following species: Yb(C8H16N2O2)3(H2O)(CF3SO3)3, compound 6, monoclinic, P2(1)/n, a = 8.9443(3) A, b = 11.1924(4) A, c = 44.2517(13) A, beta = 93.264(1) degrees, Z = 4, Dcalcd = 1.735 g cm-3; Yb(C8H16N2O2)3(H2O)(ClO4)3, compound 7, monoclinic, Cc, a = 19.2312(6) A, b = 11.1552(3) A, c = 19.8016(4) A, beta = 111.4260(1) degrees, Z = 4, Dcalcd = 1.690 g cm-3; Yb(C8H16N2O2)2(H2O)3(CF3SO3)3, compound 8, triclinic, P1, a = 8.6719(1) A, b = 12.2683(2) A, c = 19.8094(3) A, alpha = 75.815(1) degrees, beta = 86.805(1) degrees, gamma = 72.607(1) degrees, Z = 2, Dcalcd = 1.736 g cm-3. Unlike in the analogous nitrate salts, only bidentate binding of the succinamide ligand to the lanthanide metal is observed. IR spectroscopy studies in anhydrous acetonitrile suggest that the solid-state structures of these Ln-TMSA compounds are maintained in solution.     

Controlled syntheses, characterization, and reactivity of neutral and anionic lanthanide amides supported by methylene-linked bis(phenolate) ligands

A series of neutral and anionic bis(phenolate) lanthanide amides were synthesized by general metathesis reactions, and their reactivity was explored. Protolytic ligand exchange reactions of MBMPH2 (MBMP = 2,2'-methylene bis(6-tert-butyl-4-methyl-phenolate)) with [Ln{N(TMS)2}2(mu-Cl)(THF)]2 (TMS = SiMe3) afforded the desired bridged bis(phenolate) lanthanide chlorides [(MBMP)Ln(mu-Cl)(THF)2]2 [Ln = Nd (1), Yb (2)] in high isolated yields. These lanthanide chlorides were found to be useful precursors for the synthesis of the corresponding lanthanide derivatives. Reactions of 1 and 2 with 2 equiv of NaN(TMS)2 in THF produced the expected neutral bis(phenolate) lanthanide amido complexes (MBMP)Ln[N(TMS)2](THF)2 [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and 2 with LiN(TMS)2 in a 1:4 molar ratio gave the anionic bis(phenolate) lanthanide amides as discrete ion-pair complexes [Li(THF)4][(MBMP)Ln{N(TMS)2}2] [Ln = Nd (5), Yb (6)] in high isolated yields. Further study revealed that 5 and 6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH2 with [Ln{N(TMS)2}2(mu-Cl)(THF)]2 in a 2:1 molar ratio, and then with 4 equiv of nBuLi. The reactivity of the neutral and anionic bis(phenolate) lanthanide amides was comparatively investigated. It was found that the insertion reactions of carbodiimide into the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(phenolate) lanthanide guanidinate complexes [(mu-O-MBMP)Nd{(iPrN)2CN(TMS)2}]2 (7) and (MBMP)Yb[(iPrN)2CN(TMS)2] (8), respectively, in high yields, whereas the similar reaction of carbodiimide with anionic amido complex 5 provided the unexpected ligand-redistributed products, and the homoleptic ion-pair bis(phenolate) neodymium complex [Li(DME)2(THF)][(MBMP)2Nd(THF)2] (9) was finally isolated as one of the products. Furthermore, the anionic bis(phenolate) lanthanide amides showed higher catalytic activity for the polymerization of epsilon-caprolactone than the neutral ones. All of the complexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of 1-3 and 5-9 were provided by single-crystal X-ray analyses.     

Effects of lanthanide metal size and amino ligand denticity on the solvothermal systems Ln/Sn/Se/en and Ln/Sn/Se/dien (Ln = lanthanide)

Two systems, Ln/Sn/Se/en and Ln/Sn/Se/dien, were investigated under solvothermal conditions, and novel lanthanide selenidostannates [{Ce(en)(4)}(2)(μ-Se(2))]Sn(2)Se(6) (1a), [{Ln(en)(3)}(2)(μ-OH)(2)]Sn(2)Se(6) (Ln = Pr(1b), Nd(1c), Gd(1d); en = ethylenediamine), [{Ln(dien)(2)}(4)(μ(4)-Sn(2)Se(9))(μ-Sn(2)Se(6))](∞) (Ln = Ce(2a), Nd(2b)), and [Hdien][Gd(dien)(2)(μ-SnSe(4))] (2c) (dien = diethylenetriamine) were prepared and characterized. Two structural types of lanthanide selenidostannates were obtained across the lanthanide series in both systems. In the Ln/Sn/Se/en system, two types of binuclear lanthanide complex cations [Ce(2)(en)(8)(μ-Se(2))](4+) and [{Ln(en)(3)}(2)(μ-OH)(2)](4+) (Ln = Pr, Nd, Gd) were formed depending on the Ln(3+) ions. The complex cations are compensated by the [Sn(2)Se(6)](4-) anions. In the Ln/Sn/Se/dien system, coordination polymer [{Ln(dien)(2)}(4)(μ(4)-Sn(2)Se(9))(μ-Sn(2)Se(6))](∞) and ionic complex [Hdien][Gd(dien)(2)(μ-SnSe(4))] are obtained along the lanthanide series, among which the μ(4)-Sn(2)Se(9), μ-Sn(2)Se(6) and μ-SnSe(4) ligands to the Ln(3+) ions were observed. The formation of title complexes shows the effects of lanthanide metal size and amino ligand denticity on the lanthanide selenidostannates. Complexes 1a-2c exhibit semiconducting properties with band gaps between 2.08 and 2.48 eV.     

Complexes of lanthanide nitrates with bis(diphenylphosphino)methane dioxide

The reactions of lanthanide nitrates, Ln(NO(3))(3), with bis(diphenylphosphino)methane dioxide, Ph(2)P(O)CH(2)P(O)Ph(2) (L), lead to complexes with three distinct classes of structure. At low ratios of Ln:L (<1:1.5) in acetonitrile the ionic complexes [Ln(NO(3))(2)L(2)](+)[Ln(NO(3))(4)L](-) (Ln = Pr, Eu) have been isolated. When carried out with a 1:2 or higher ratio in ethanol the reaction yields Ln(NO(3))(3)L(2) (Ln = La,Ce) and [Ln(NO(3))(2)L(2)H(2)O](+)[NO(3)](-) (Ln = Nd, Gd, Ho). Geometrical isomerism is found for the cations [Ln(NO(3))(2)L(2)H(2)O](+) and is attributed to the extent of hydrogen bonding to the coordinated water. Ligand redistribution occurs on heating in the solid state giving yellow solids in all cases. Crystallization of these materials from ethanol or acetonitrile gives [Ln(NO(3))L(3)](2+).2[NO(3)](-), which have been structurally characterized for Ln = Gd and Yb. Electrospray mass spectra indicate that extensive ligand exchange reactions occur in solution.     

Self-assembly of lanthanide mixed-carboxylates coordination polymers

Two new mixed-ligands lanthanide coordination polymers, [Ln(Ac)(ip)(H₂O)₂]·0.5H₂O (Ln=La (1); Ln=Eu (2); Ac=acetate; ip=isophthalate) have been synthesized under hydrothermal condition. Single-crystal X-ray analyses show that complexes 1 and 2 are three-dimensional structure in which lanthanide ions are bridged by monocarboxylate ligand, acetate or dicarboxylate ligand, isophthalate. And the central lanthanide ions, La³⁺ and Eu³⁺, are both nine-coordinate with oxygen atoms. The thermogravimetric analysis was carried out to examine the thermal stability of the title complexes. And the photoluminescence property of complex 2 was also investigated.     

Synthesis and structural characterization of nonanuclear lanthanide complexes

A series of nonanuclear lanthanide oxo-hydroxo complexes of the general formula [Ln(9)(mu(4)-O)(2)(mu(3)-OH)(8)(mu-BA)(8)(BA)(8)](-)[HN(CH(2)CH(3))(3)](+).(CH(3)OH)(2)(CHCl(3)) (BA = benzoylacetone; Ln = Sm, 1; Eu, 2; Gd, 3; Dy, 4; Er, 5) were prepared by the reaction of hydrous lanthanide trichlorides with benzoylacetone in the presence of triethylamine in methanol and recrystallized from chloroform/methanol (1:10) at room temperature. These five compounds are isomorphous. Crystal data for 1: cubic, Pn3n; T = 180 K; a = 33.8652(4) A; V = 38838.4(8) A(3); Z = 6; D(calcd) = 1.125 g cm(-)(3); R1 = 3.37%. Crystal data for 2: cubic, Pn3n; T = 180 K; a = 33.8252(8) A; V = 38700.9(16) A(3); Z = 6; D(calcd) = 1.133 g cm(-)(3); R1 = 4.97%. Crystal data for 3: cubic, Pn3n; T = 180 K; a = 33.7061(6) A; V = 38293.5(12) A(3); Z = 6; D(calcd) = 1.157 g cm(-)(3); R1 = 5.13%. Crystal data for 4: cubic, Pn3n; T = 180 K; a = 33.5900(7) A; V = 37899.2(14) A(3); Z = 6; D(calcd) = 1.182 g cm(-)(3); R1 = 4.03%. Crystal data for 5: cubic, Pn3n; T = 180 K; a = 33.5054(8) A; V = 37613.6(16) A(3); Z = 6; D(calcd) = 1.202 g cm(-)(3); R1 = 4.86%. The core of the anionic cluster comprises two vertex-sharing square-pyramidal [Ln(5)(mu(4)-O)(mu(3)-OH)(4)](9+) units. The compounds were characterized by elemental analysis, IR, fast atom bombardment mass spectra, thermogravimetry, and differential scanning calorimetry. The thermal analysis indicated that the nonanuclear species were stable up to 150 degrees C. Luminescence spectra of 2 and magnetic properties of 1-5 were also studied.     

Controlled hydrolysis of lanthanide complexes of the N-donor tripod tris(2-pyridylmethyl)amine versus bisligand complex formation

The reaction of the lanthanide salts LnI3(thf)4 and Ln(OTf)3 with tris(2-pyridylmethyl)amine (tpa) was studied in rigorously anhydrous conditions and in the presence of water. Under rigorously anhydrous conditions the successive formation of mono- and bis(tpa) complexes was observed on addition of 1 and 2 equiv of ligand, respectively. Addition of a third ligand equivalent did not yield additional complexes. The mono(tpa) complex [Ce(tpa)I3] (1) and the bis(tpa) complexes [Ln(tpa)2]X3 (X = I, Ln = La(III) (2), Ln = Ce(III) (3), Ln = Nd(III) (4), Ln = Lu(III) (5); X = OTf, Ln = Eu(III) (6)) were isolated under rigorously anhydrous conditions and their solid-state and solution structures determined. In the presence of water, 1H NMR spectroscopy and ES-MS show that the successive addition of 1-3 equiv of tpa to triflate or iodide salts of the lanthanides results in the formation of mono(tpa) aqua complexes followed by formation of protonated tpa and hydroxo complexes. The solid-state structures of the complexes [Eu(tpa)(H2O)2(OTf)3] (7), [Eu(tpa)(mu-OH)(OTf)2]2 (8), and [Ce(tpa)(mu-OH)(MeCN)(H2O)]2I4 (9) have been determined. The reaction of the bis(tpa) lanthanide complexes with stoichiometric amounts of water yields a facile synthetic route to a family of discrete dimeric hydroxide-bridged lanthanide complexes prepared in a controlled manner. The suggested mechanism for this reaction involves the displacement of one tpa ligand by two water molecules to form the mono(tpa) complex, which subsequently reacts with the noncoordinated tpa to form the dimeric hydroxo species.     

Tuning the self-assembly of lanthanide triple stranded heterobimetallic helicates by ligand design

The heterobitopic ligands L(AB4) and L(AB5) have been designed and synthesised with the ultimate aim of self-assembling dual-function lanthanide complexes containing either a magnetic and a luminescent probe or two luminescent probes emitting at different wavelengths. They react with lanthanide ions to form complexes of composition [Ln(2)(L(ABX))(3)](6+) of which three (X = 4; Ln = Pr, Nd, Sm) have been isolated and characterised by means of X-ray diffraction. The unit cells contain triple-stranded helicates in which the three ligand strands are wrapped tightly around the two lanthanide ions. In acetonitrile solution the ligands form not only homobimetallic, but also heterobimetallic complexes of composition [Ln(1)Ln(2)(L(ABX))(3)](6+) when reacted with a pair of different lanthanide ions. The yield of heterobimetallic complexes is analyzed in terms of both the difference in ionic radii of the lanthanide ions and of the inherent tendency of the ligands to form high percentages of head-head-head (HHH) helicates in which all three ligand strands are oriented in the same direction with respect to the Ln-Ln vector. The latter is very sensitive to slight modifications of the tridentate coordinating units.