Solid-State and solution studies of [Ln(n)(SiW11O39)] polyoxoanions: an example of building block condensation dependent on the nature of the rare earth

The reactivity of the [alpha-SiW(11)O(39)](8-) monovacant polyoxometalate with lanthanide has been investigated for four different trivalent rare-earth cations (Ln = Nd(III), Eu(III), Gd(III), Yb(III)). The crystal structures of KCs(4)[Yb(alpha-SiW(11)O(39))(H(2)O)(2)] x 24H(2)O (1), K(0.5)Nd(0.5)[Nd(2)(alpha-SiW(11)O(39))(H(2)O)(11)] x 17H(2)O (2a), and Na(0.5)Cs(4.5)[Eu(alpha-SiW(11)O(39))(H(2)O)(2)] x 23H(2)O (3a) are reported. The solid-state structure of compound 1 consists of linear wires built up of [alpha-SiW(11)O(39)](8-) anions connected by Yb(3+) cations, while the linkage of the building blocks by Eu(3+) centers in 3a leads to the formation of zigzag chains. In 2a, dimeric [Nd(2)(alpha-SiW(11)O(39))(2)(H(2)O)(8)](10-) entities are linked by four Nd(3+) cations. The resulting chains are connected by lanthanide ions, leading to a bidimensional arrangement. Thus, the dimensionality, the organization of the polyoxometalate building units, and the Ln/[alpha-SiW(11)O(39)](8-) ratio in the solid state can be tuned by choosing the appropriate lanthanide. The luminescent properties of compound 3a have been studied, showing that, in solution, the polymer decomposes to give the monomeric complex [Eu(alpha-SiW(11)O(39))(H(2)O)(4)](5-). The lability of the four exogenous ligands connected to the rare earth must allow the functionalization of this lanthanide polyanion.     

A rare earth-DOTA-binding antibody: probe properties and binding affinity across the lanthanide series

An antibody that binds rare earth complexes selectively could be used as a docking station for a set of probe molecules, of particular interest for medical imaging and therapy. The rare earths are rich in probe properties, such as the paramagnetism of Gd, the luminescence of Tb and Eu, and the nuclear properties of Lu and Y. We find that antibody 2D12.5, initially developed to bind analogues of Y-DOTA (1,4,7,10-tetraazacyclododecane-N,N',N' ',N' '-tetraacetic acid) for radiotherapy, binds not only Y-DOTA analogues but also analogous DOTA complexes of all of the lanthanides. Surprisingly, chelates of some metals such as Gd3+ bind more tightly than the original Y3+ complex. When the shape of the complex is perturbed by either increasing or decreasing the radius of the lanthanide ion, the thermodynamic stability of the protein-ligand complex changes in a regular fashion. The behavior of DeltaDeltaG as a function of ionic radius fits a parabola, as might be expected for a system that behaves in a thermodynamically elastic way. The broad specificity and high affinity of this antibody for all rare earth-DOTA complexes make it particularly interesting for applications that take advantage of the unique characteristics of lanthanides. For example, UV excitation of the Tb-DOTA-2D12.5 complex leads to energy transfer from aromatic side chains of the antibody to bound Tb-DOTA, enhancing green terbium luminescence >104 relative to unbound Tb-DOTA.     

Synthesis, structure and luminescent properties of rare earth coordination polymers constructed from paddle-wheel building blocks

A series of three-dimensional (3D) novel coordination polymers M(bpdc)1.5(H2O) x 0.5DMF (M = Tb (1), Ho (2), Er (3), or Y (4)) have been synthesized by reaction of the rare earth ions (M3+) with 4,4'-biphenyldicarboxylic acid (H2bpdc) in a mixed solution of DMF and C2H5OH. They possess the same 3D architectures and crystallize in monoclinic space group C2/c. Two seven-coordinated metal centers and four dimonodentate bpdc groups construct a paddle-wheel building block. These building blocks connect with two carboxyl groups to lead to a one-dimensional inorganic chain, ---M-O-C-O-M---, along the [001] direction. The inorganic chains are linked with two biphenyl groups to form 25.15 A x 17.09 A rhombic channels along the c axis without interpenetration. These complexes exhibit strong fluorescence in the visible region, and complex 3 shows Er3+ characteristic emission in the range of 1450-1650 nm at room temperature. These complexes could be anticipated as potential fluorescent probes and an IR-emitter, respectively.     

A novel series of vanadium-sulfite polyoxometalates: synthesis, structural, and physical studies

Reaction of NH4VO3 with sulfur dioxide affords the hexanuclear cluster (NH4)2(Et4N)[(V(IV)O)6(mu4-O)2(mu3-OH)2(mu3-SO3)4(H2O)2]Cl x H2O (1), and the decapentanuclear host-guest compound (Et4N)5{Cl subset [(VO)15(mu3-O)18(mu-O)3]} x 3 H2O (2). Sequential addition of magnesium oxide to an acidic aqueous solution of NH4VO3 (pH approximately 0) followed by (NH4)2SO3 resulted in the formation of either the non-oxo polymeric vanadium(IV) compound trans-(NH4)2[V(IV)(OH)2(mu-SO3)2] (3) or the polymeric oxovanadium(IV) sulfite (NH4)[V(IV)O(SO3)1.5(H2O)] x 2.5 H2O (4) at pH values of 6 and 4, respectively. The decameric vanadium(V) compound {Na4(mu-H2O)8(H2O)6}[Mg(H2O)6][V(V)10(O)8(mu6-O)2(mu3-O)14] x 3 H2O (5) was synthesised by treating an acidic aqueous solution of NH4VO3 with MgO and addition of NaOH to pH approximately 6. All the compounds were characterised by single-crystal X-ray structure analysis. The crystal structure of compound 1 revealed an unprecedented structural motif of a cubane unit [M4(mu4-O)2(mu3-OH)2] connected to two other metal atoms. Compound 3 comprises a rare example of a non-oxo vanadium(IV) species isolated from aqueous solution and in the presence of the reducing agent SO3(2-), while compound 4 represents a rare example of an open-framework species isolated at room temperature (20 degrees C). In addition to the synthesis and crystallographic studies, we report the IR and magnetic properties (for 1, 2 and 3) of these vanadium clusters as well as theoretical studies on compound 3.     

Anisotropic distribution of cations in the structures of rare earth compounds

Anisotropic cationic networks, which constitute the left-hand side of the binary opposition with isotropic cationic networks, are topologically identical in the structures of quite different rare earth compounds.     

A single structural type in the series of oxyorthosilicates of the rare earth elements

Summary We have carried out a roentgenostructural analysis of monocrystals and polycrystals of the oxyorthosilicates of rare earth elements of the third group. of rare earth elements of the third group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 925–926, May, 1965 Original article submitted August 22, 1964     

稀土配合物的研究 I: 镧系元素与4-酰代-双吡唑啉酮及1,10-二氮杂菲的混配配合物的合成及表征

用镧系硝酸盐与1,6-双(1'-苯基-3'-甲基-5'-氧代吡唑-4'-基)-1,6-己二酮(1,H2L)和1,10-二氮杂菲(2, Phen)在乙醇-水溶液中, 于PH5-6时合成了12种新的固态配合物Ln2L3Phen2. 4H2O(Ln=Pr, Nd, Sm-Lu)。用元素分析、水份及配体分析、红外、紫外,质子核磁共振、荧光光谱和热分析鉴定了所有的配合物, 从而推测, 可能L是四啮配体,Phen是二啮配体。     

A principle for the assembly of novel mononuclear building blocks for supramolecular chemistry

Abstract

The controlled assembly of supramolecular coordination oligomers may be achieved by the use of multinucleating ligands which contain two or more metal-binding domains. Examples of such ligands commonly consist of discrete metal-binding sites linked by appropriate spacers. We now show that a consideration of the donor properties of a ligand and the acceptor properties of a metal ion may be used to induce multinucleating behaviour in oligopyridine ligands which conventionally chelate to single metal centres. Such species are key building blocks for the assembly of a variety of supramolecular species in which the non-coordinated donor atoms may later interact with other metal centres. The crystal structure of the complex [Ru(bpy-N,N′)₂(tpy-N,N′)][PF₆]₂ ( P 1, a = 8.367(2), b = 11.821(4), c = 19.398(5)Å, α = 93.83(2), β = 92.25(2), γ = 89.62(2)°, Z = 2, d _c = 1.63 g cm^?3, 5084 unique observed reflections with I < 1.5σ(I), R = 0.0745) which contains a bidentate tpy ligand is presented.     

A series of three-dimensional architectures constructed from lanthanide-substituted polyoxometalosilicates and lanthanide cations or lanthanide-organic complexes as linkers

Six 3D architectures based on lanthanide-substituted polyoxometalosilicates, KLn[(H(2)O)(6)Ln](2)[(H(2)O)(4)LnSiW(11)O(39)](2)·nH(2)O (Ln = La 1, n = 42; Ce 2, n = 40), H[(H(2)O)(6)Nd](2)[(H(2)O)(7)Nd][(H(2)O)(4)NdSiW(11)O(39)][(H(2)O)(3)NdSiW(11)O(39)]·13H(2)O (3), H(2)K(2)[(Hpic)(H(2)O)(5)Ln](2)[(H(2)O)(4)LnSiW(11)O(39)](2)·nH(2)O (Ln = La 4, n = 18.5; Ce 5, n = 35; Nd 6, n = 36; Hpic = 4-picolinic acid), have been synthesized and characterized by elemental analysis, IR and UV-vis spectroscopy, TG analysis, powder X-ray diffraction and single crystal X-ray diffraction. Compounds 1 and 2 are isostructural, built up of lanthanide-substituted polyoxoanions [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) linked by Ln(3+) cations to form a 3D open framework with 1D channels. The polyoxoanion [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) consists of two α(1)-type mono-Ln-substituted Keggin anions. When Nd(3+) ion was used instead of La(3+) or Ce(3+) ions, compound 3 with a different structure was obtained, containing two kinds of polyoxoanions [{(H(2)O)(4)Nd(SiW(11)O(39))}(2)](10-) and [{(H(2)O)(3)Nd(SiW(11)O(39))}(2)](10-) which are connected together by Nd(3+) ions to yield a 3D framework. When 4-picolinic acid was added to the reaction system of 1-3, isostructural compounds 4-6 were obtained, constructed from the polyoxoanions [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) linked by picolinate-chelated lanthanide centers to form a 3D channel framework. From a topological viewpoint, the 3D nets of 1, 2, 4, 5 and 6 exhibit a (3,6)-connected rutile topology, whereas the 3D structure of 3 possesses a rare (3,3,6,10)-connected topology. The magnetic properties of 2, 3, 5 and 6 have been studied by measuring their magnetic susceptibilities in the temperature range 2-300 K.     

Phenanthroline dipyrromethene conjugates: potential building blocks for the construction of novel supramolecular architectures

Novel tritopic ligands, based on dipyrromethenes and the 1,10-phenanthroline nucleus, as well as BF₂ complexes derived thereof are described. While BODIPY dyes 9-12 have been successfully prepared, the structural features of the free ligands 7 and 8 may render them useful as precursors for the elaboration of novel supramolecular architectures.     

A comparison of the effect of rare earth vs Si site doping on the conductivities of apatite-type rare earth silicates

Apatite-type lanthanum silicate (La_9.33Si₆O₂₆) has been attracting significant recent interest due to its high oxide ion conductivity. In this paper, synthesis and conductivity data for a range of doped samples (Mg, Ca, Sr, Ba, B, Ga and Zn) are reported, in particular, to compare the effect of rare earth vs Si site doping. The results show that Ga, B and Zn favour substitution on the Si site, while Ca, Sr and Ba favour La-site substitution. Mg is shown to be an ambi-site dopant, substituting on either site depending on the starting composition. The samples doped on the Si site show higher conductivities than comparable samples doped on the La site, providing further support for the importance of the silicate network in the conduction process, as initially predicted by atomistic modelling studies. For Ga doping on the Si site, the effect of varying the rare-earth size on the conductivities is also reported.     

A novel efficient approach to heteronuclear triple-decker complexes of rare earth elements with phthalocyanines

A novel approach to heteroleptic heteronuclear rare earth metal(III) trisphthalocyaninates was proposed with the complexes [(15C5)₄Pc]M*[(15C5)₄Pc]M(Pc) as examples (15C5 is 15-crown-5, Pc^2? is the phthalocyaninate dianion, and M* ?? M = Yb and Y). Unsubstituted lanthanum bisphthalocyaninate, La(Pc)₂, was used for the first time as a Pc^2? donor in the synthesis of such complexes. This substantially increased the yields of the target heteronuclear complexes over the previous literature data.     

Interactions of trivalent lanthanide cations with a hexadentate Schiff base derived from the condensation of ethylenediamine with 8-hydroxyquinoline-2-carboxaldehyde

Lanthanide(III) complexes [Ln(NO₃)₂(HL)] where Ln?=?La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb and Lu and LH₂?=?N,N′-bis(quinolin-8-ol-2-ylmethylidene)ethane-1,2-diamine, have been obtained by direct reaction of the di-Schiff base ligand and the corresponding hydrated lanthanide(III) nitrates in methanol/DMF solvent systems. All complexes were characterized with microanalyses, spectroscopically (IR and electronic spectra) and thermogravimetrically. Theoretical studies have also been undertaken to estimate possible structures. All the data are discussed in terms of the nature of the bonding and the possible structural types. All complexes appear to be monomeric with the organic ligand being singly deprotonated and behaving as a hexadentate chelating ligand.     

三水合稀土氯化物RECl3·3H2O的热化学研究

本文报道了一套化学反应绝热式热量计的设计和建立, 用(HOCH2)3CNH2与0.1mol·dm^-^3HCl的反应焓检验标定了热量计装置, 测得ΔH298.5=-245.41J·g^-^1, sdm=±0.24, 与IUPAC的推荐值-245.76±0.26J·g^-^1十分吻合, 证明热量计和操作手续是可靠的。用这样的热量计测定了十一种三水合稀土氯化物RECl3·3H2O(RE=La, Ce, Nd,Sm, Eu, Gd, Tb, Dy, er, Yb, Y)298.15K时在水中的积分溶解热(终浓度=0.01541mol·kg^-^1)。计算了这些水合物的标准生成焓和脱水焓。     

A synthetic approach to polyene macrolldes: Synthesis of the building blocks

The two building blocks required to construct the 26-membered ring skeleton of tetrin-A have been synthesized.     

Binuclear ladder-type complexes as building blocks for the synthesis of novel polynuclear systems

Summarized are reactivity studies of binuclear ladder complexes in the metallation reaction that has been applied to prepare novel homo- and heteropolynuclear transition metal complexes. The electron transfer through π-ligand-metal-σ,π-ligand-metal chain has been studied by IR spectroscopy and cyclic voltammetry techniques.     

Nanoscale building blocks for the development of novel proton exchange membrane fuel cells

We propose a new type of sulfonated aromatic polyarylenes as candidate building blocks for proton exchange membranes. Density functional theory calculations and ab initio molecular dynamics simulations suggest that desulfonation is limited at high temperatures, owing to the strong aryl-SO3H bond induced by the electron-deficient aromatic ring, and that the proposed polymers exhibit good thermomechanical stability due to the robust aromatic main-chain repeating unit. Simulations also emphasize the importance of the Grotthuss-type mechanism, with interconversion between Eigen (H9O4+) and Zundel cations (H5O2+) as limiting structures, for the hydrated proton transport in the vicinity of the sulfonic acid groups.     

Expanding the azaspiro[3.3]heptane family: synthesis of novel highly functionalized building blocks

The preparation of versatile azaspiro[3.3]heptanes carrying multiple exit vectors is disclosed. Expedient synthetic routes enable the straightforward access to these novel modules that are expected to have significance in drug discovery and design.     

Antiferromagnetic coupling between rare earth ions and semiquinones in a series of 1:1 complexes

We use the strategy of diamagnetic substitution for obtaining information on the crystal field effects in paramagnetic rare earth ions using the homologous series of compounds with the diamagnetic tropolonato ligand, Ln(Trp)(HBPz(3))(2), and the paramagnetic semiquinone ligand, Ln(DTBSQ)(HBPz(3))(2), (DTBSQ = 3,5-di-tert-butylsemiquinonato, Trp = tropolonate, HBPz(3)= hydrotrispyrazolylborate) for Ln = Sm(iii), Eu(iii), Gd(iii), Tb(iii), Dy(iii), Ho(iii), Er(iii) or Yb(iii). The X-ray crystal structure of a new form of tropolonate derivative is presented, which shows, as expected, a marked similarity with the structure of the semiquinonate derivative. The Ln(Trp)(HBPz(3))(2) derivatives were then used as a reference for the qualitative determination of crystal field effects in the exchange coupled semiquinone derivatives. Through magnetisation and susceptibility measurements this empirical diamagnetic substitution method evidenced for Er(iii), Tb(iii), Dy(iii) and Yb(iii) derivatives a dominating antiferromagnetic coupling. The increased antiferromagnetic contribution compared to other radical-rare earth metal complexes formed by nitronyl nitroxide ligands may be related to the increased donor strength of the semiquinone ligand.     

Gas-phase reactivity of rare earth cations with phenol: Competitive activation of C-O, O-H, and C-H bonds

The gas-phase reactions of Sc⁺, Y⁺, and Ln⁺ (Ln=La-Lu, except Pm) ions with phenol were studied by Fourier transform ion cyclotron resonance mass spectrometry. All the ions except Yb⁺ were observed to react with the organic substrate, activating O-H, C-O, and/or C-H bonds, with formation of MO⁺, MOH⁺, and/or MOC₆H ₄ ⁺ ions as primary products. The product distributions and the reaction efficiencies obtained showed the existence of important differences in the relative reactivity of the rare earth metal cations, which are discussed in terms of factors like the electron configurations of the metal ions, their oxophilicity, and the second ionization energies of the metals. The primary product ions participated in subsequent reactions, yielding species such as M(OH)(OC₆H₅)⁺, which lead mainly to M(OC₆H₅)₂(HOC₆H₅) _n ⁺ ions, where n=0–2. Formation of M(OC₆H₅)(HOC₆H₅) _n ⁺ species was also observed in the case of the metals that have high stabilities of the formal oxidation state 2+, Sm and Eu.