Studies of Dehydration Process for Isostructural Series of Lanthanide(III) 2,6-dihydroxybenzoates

Dehydration kinetics of lanthanide 2,6-dihydroxybenzoates has been studied by thermogravimetry using the model-fitting method of calculation. Several kinetic models gavea good representation of the measured thermogravimetric (TG) curves but the calculation method allowed to propose the most probable dehydration mechanism. The activation energies of dehydration for isostructural 2,6-dihydroxybenzoates of lanthanides are similar for a given kinetic model. A change in the heating rate did not alter the dehydration mechanism. A linear correlation between the activation energy and the heating rate was observed for the systems studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lanthanide(III) Nitrate Complexes of Two 17 Membered N3O2-Donor Macrocycles

The interaction of lanthanide(III) ions with two N₃O₃-macrocycles, L¹ and L², derived from 2,6-bis(2-formylphenoxymethyl)pyridine and 1,2-diaminoethane has been investigated. Schiff-base macrocyclic lanthanide(III) complexes LnL¹(NO₃)₃ · xH₂O (Ln = Nd, Sm, Eu or Lu) have been prepared by direct reaction of L¹ and the appropriate hydrated lanthanide nitrate. The direct reaction between the diamine macrocycle L² and the hydrated lanthanide(III) nitrates yields complexes LnL²(NO₃)₃· H₂O only for Ln = Dy or Lu. The reduction of the Schiff-base macrocycle decreases the complexation capacity of the ligand towards the Ln(III) ions. The complexes have been characterised by elemental analysis, molar conductivity data, FAB mass spectrometry, IR and, in the case of the lutetium complexes, ¹H NMR spectroscopy.     

Kinetics and Mechanism of Dehydration of Heteropolyacids

The kinetics and mechanism of the dehydration and decomposition of heteropolyacids of molybdenum, tungsten and vanadium (H3+xYx+M12O40·mH2O; Y=Si, P; M=Mo, W) were studied. The data obtained on the dehydration kinetic parameters correlate with the expected structures, of these crystal hydrates, the IR data and X-ray phase analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal investigations of dehydration of lanthanide(iii) 5-nitroanthranilates

The 5-nitro-2-anthranilates of lanthanum(III), samarium(III), terbium(III), erbium(III) and lutetium(III) were obtained as hydrates having 2.5 mol of water molecules per 1 mol of compound. The compounds are isostructural. The processes of dehydration and rehydration were investigated. The first step of dehydration does not cause the change of crystal structure. The entire dehydration gives anhydrous compounds with different structure than the structure of hydrates. However, the dehydration of La, Sm, Tb and Er is reversible - the rehydration process gives the complexes having the same crystal structure as the initial compounds. Only the anhydrous lutetium complex under the influence of moisture does not give the starting compound. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lanthanide Complexes with Acetylacetone and 5-(4-Nitrophenyl)-10,15,20-Triphcnylporphyrin Ligands

Sincethefirstlanthanideporphyrinwassynthesizedin1974',anumberofthisclassofporphyrinshavebeensynthesized'.Becauselanthanideionhasspecialelectronstructure,peopleareinterestedinpropertiesoflanthanideporphyrincomplexessuchascatalyticfunction,opticalstorage,etc3.Ingeneral,moresymmetricallyfunctionallanthanideporphyrinshavebeenstudied,butfewerunsymmetricallanthanideporphyrinsarereported.Nowlanthanidecomplexesofunsymmetricallymeso-substitutedphenylporphyrinacetylacetonate5-(4-nitrophenyl)-10,15,20-tr…     

Thermal Studies on Lanthanide Nitrate Complexes of 4-n-(2′-furfurylidene)aminoantipyrine

The kinetics and mechanism of thermal decomposition of nitrate complexes of lanthanides with the Schiff base4-N-(2′-furfurylidene) aminoantipyrine (abbreviated as FAA) have been studied by TG and DTG techniques. The kinetic data for the first stage of decomposition were calculated using the Coats-Redfern equation. The rate-controlling process obeys Mampel model representing random nucleation, with one nucleus on each particle. It is observed that there is no gradation in the values of the kinetic parameters of decomposition of the complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dehydration Kinetics of Zinc Phosphate Tetrahydrate α-Zn3（PO4）2·4H2O Nanoparticle

TG-DTG technique and Harcourt-Esson integrated equation were used to study the dehydration process of zinc phosphate tetrahydrate α-Zn3（PO4）2·4H2O nanoparticle and its thermal decomposition kinetics. The results show that there are three stages of dehydration between 300 and 800 K during the thermal decomposition of α-Zn3（PO4）2·4H2O nanoparticle. The first stage is controlled by chemical reaction with an activation energy of 69.48 kJ·mol^-1 and a pre-exponential factor of 1.77×10^6 s^-1. The second is controlled by nucleation and growth with an activation energy of 78.74 kJ·mol^-1 and a pre-exponential factor of 5.86×10^9 s^-1. The third is controlled by nucleation and growth with an activation energy of 141.5 kJ·mol^-1 and a pre-exponential factor of 1.01×10^12 s^-1. The kinetic compensative effects not only exist in Arrhenius equation but also in Harcourt-Esson equation. Activation energy E is dependent on both the decomposition fraction α and temperature T.     

Six‐Coordinate Lanthanide Complexes: Slow Relaxation of Magnetization in the Dysprosium(III) Complex

A series of six‐coordinate lanthanide complexes {(H₃O)[Ln(NA)₂]?H₂O}_n (H₂NA=5‐hydroxynicotinic acid; Ln=Gd^III ( 1?Gd ); Tb^III ( 2?Tb ); Dy^III ( 3?Dy ); Ho^III ( 4?Ho )) have been synthesized from aqueous solution and fully characterized. Slow relaxation of the magnetization was observed in 3?Dy . To suppress the quantum tunneling of the magnetization, 3?Dy diluted by diamagnetic Y^III ions was also synthesized and magnetically studied. Interesting butterfly‐like hysteresis loops and an enhanced energy barrier for the slow relaxation of magnetization were observed in diluted 3?Dy . The energy barrier (Δ_τ) and pre‐exponential factor (τ₀) of the diluted 3?Dy are 75 K and 4.21×10^?5 s, respectively. This work illustrates a successful way to obtain low‐coordination‐number lanthanide complexes by a framework approach to show single‐ion‐magnet‐like behavior.     

Thermal Decomposition and Dehydration Kinetics of Tetra(piperidinium) Octamolybdate Tetrahydrate in Air

Thermal decomposition of tetra(piperidinium) octamolybdate tetrahydrate, [C₅H₁₀NH₂]₄[Mo₈O₂₆]·4H₂O, was investigated in air by means of TG‐DTG/DTA, DSC, TG‐IR and SEM. TG‐DTG/DTA curves showed that the decomposition proceeded through three well‐defined steps with DTA peaks closely corresponding to mass loss obtained. Kinetics analysis of its dehydration step was performed under non‐isothermal conditions. The dehydration activation energy was calculated through Friedman and Flynn‐Wall‐Ozawa (FWO) methods, and the best‐fit dehydration kinetic model function was estimated through the multiple linear regression method. The activation energy for the dehydration step of [C₅H₁₀NH₂]₄[Mo₈O₂₆]·4H₂O was 139.7 kJ/mol. The solid particles became smaller accompanied by the thermal decomposition of the title compound.     

Thermoanalytical Study of the Dehydration of Cyclodextrin Inclusion Complexes of Clofibric Acid

Hydrated inclusion complexes of the hosts β-CD (CD=cyclodextrin), γ-CD and permethylated β-CD with the guest clofibric acid were analysed by TG and DSC methods to characterise their dehydration behaviours. Activation energies for dehydration of the β- and γ-CD clofibric acid complexes, determined by isothermal thermogravimetry, are significantly lower (∼20-25%) than those for the corresponding uncomplexed hydrated CDs. These data can be reconciled with X-ray structural data which show that H₂O molecules in the complexes occupy different crystal sites from those occupied in the parent CDs. This revised version was published online in August 2006 with corrections to the Cover Date.     

Lanthanide(III) Complexes with Pyridine Head Macrocyclic Ligands

The ability of lanthanide(III) ions to form stable complexeswith three different macrocyclic ligands, L¹ , L² and L³ , has been investigated.The Schiff base macrocycle L¹ and its corresponding reduced ligand L² arederived from 2,6-bis(2-formylphenoxymethyl)pyridine and diethylentriamine;the reduced ligand L³ is derived from 2,6-diformylpyridine and N,N-bis(3-aminopropyl)methylamine. Lanthanide nitrate complexes of L¹ and L² have beenprepared by direct reaction between each ligand and the appropriate hydrated lanthanidenitrate; attempts to obtain the corresponding perchlorate complexes have been unsuccessful.All nitrate complexes of L¹ give the expected [1:1, Ln:L¹ ] stoichiometry; however, complexes obtained with L² show a [2:1, Ln:L² ] stoichiometry. Finally, complexation reactions with L³ have been carried out in order to investigatethe coordination capability of this small and flexible ligand towards the Ln(III) ions.     

[Nd(SSCNH2)4]-的电子结构 一种有机硫配位镧系络合物的模型阴离子

本文详细研究了络阴离子{Nd[SSCN(C_2H_5)_2]_4}~-的简化模型[Nd(SSCNH_2)_4]~-的电子结构和化学键合情况。从对键能的贡献看, 钕和硫原子之间的结合主要是离子性的, 但从电荷的重新分布看,应该认为共价结合对成键有一定贡献。σ键起主要作用, 对Nd—S和Nd—S′键来说, π键级只有σ键级的1/5～1/6。根据计算结果分析了为什么至今只合成了很少几种有机硫配位镧系络合物而存在大量稳定无机复合镧系硫化物的原因。建议了几种合成稳定的有机硫配位镧系络合物的可能途径。     

Dinuclear Lanthanide(III) Complexes from the Use of Methyl 2-Pyridyl Ketoxime: Synthetic,Structural, and Physical Studies

The first use of methyl 2-pyridyl ketoxime (mepaoH) in homometallic lanthanide(III) [Ln(III)] chemistry is described. The 1:2 reactions of Ln(NO₃)₃·nH₂O (Ln = Nd, Eu, Gd, Tb, Dy; n = 5, 6) and mepaoH in MeCN have provided access to complexes [Ln₂(O₂CMe)₄(NO₃)₂(mepaoH)₂] (Ln = Nd, 1; Ln = Eu, 2; Ln = Gd, 3; Ln = Tb, 4; Ln = Dy, 5); the acetato ligands derive from the Ln^III—mediated hydrolysis of MeCN. The 1:1 and 1:2 reactions between Dy(O₂CMe)₃·4H₂O and mepaoH in MeOH/MeCN led to the all-acetato complex [Dy₂(O₂CMe)₆(mepaoH)₂] (6). Treatment of 6 with one equivalent of HNO₃ gave 5. The structures of 1, 5, and 6 were solved by single-crystal X-ray crystallography. Elemental analyses and IR spectroscopy provide strong evidence that 2–4 display similar structural characteristics with 1 and 5. The structures of 1–5 consist of dinuclear molecules in which the two Ln^III centers are bridged by two bidentate bridging (η¹:η¹:μ₂) and two chelating-bridging (η¹:η²:μ₂) acetate groups. The Ln^III atoms are each chelated by a N,N’-bidentate mepaoH ligand and a near-symmetrical bidentate nitrato group. The molecular structure of 6 is similar to that of 5, the main difference being the presence of two chelating acetato groups in the former instead of the two chelating nitrato groups in the latter. The geometry of the 9-coordinate Ln^III centers in 1, 5 and 6 can be best described as a muffin-type (MFF-9). The 3D lattices of the isomorphous 1 and 5 are built through H-bonding, π⋯π stacking and C-H⋯π interactions, while the 3D architecture of 6 is stabilized by H bonds. The IR spectra of the complexes are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The Eu(III) complex 2 displays a red, metal-ion centered emission in the solid state; the Tb^III atom in solid 4 emits light in the same region with the ligand. Magnetic susceptibility studies in the 2.0–300 K range reveal weak antiferromagnetic intramolecular Gd^III…Gd^III exchange interactions in 3; the J value is −0.09(1) cm⁻¹ based on the spin Hamiltonian Ĥ = −J(Ŝ_Gd1·Ŝ_Gd2).     

Kinetics of Gypsum Dehydration

The kinetics of gypsum dehydration in non-isothermal conditions with constant heating rate as well in quasi-isotherm, quasi-isobar regime, was investigated. The latter ones of these methods allowed putting in evidence the autocatalytic character of the dehydration, as well as the change of the activation energy with the conversion.The activation energy change was explained by the crystal growth and sample compaction observed by optical microscopy.Microscopic observations show that at higher conversions a compaction occur. This process is probably favoured by the accumulation of the water vapour from the dehydration (autogenerate atmosphere). These are the reason for step III characterised by higher activation.This revised version was published online in November 2005 with corrections to the Cover Date.     

Spirocyclic Boraamidinate Complexes of Lanthanide(III) Metals

The reaction of Li₂[Phbam^Dipp] (Phbam^Dipp = PhB(NDipp)₂; Dipp = 2,6‐iPr₂C₆H₃) with lanthanum(III) triiodides LnI₃(THF)_3.5 (Ln = La, Sm) in THF produces complexes of the type [Li(THF)₄]₂[(Phbam^Dipp)₂LnI], which were characterized in solution by multinuclear NMR spectroscopy and in the solid state by single‐crystal X‐ray structural determinations. The ion‐separated complexes are comprised of a spirocyclic anion in which two Phbam^Dipp ligands and an iodide ion are linked to the five‐coordinate metal atom; charge balance is provided by two tetrasolvated lithium ions [Li(THF)₄]⁺.     

Synthesis,Characterization, Antimicrobial Activities,and Structural Studies of Lanthanide (III) Complexes with 1-(4-Chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1-thiosemicarbazone

Twelve coordinate lanthanide (III) complexes with the general composition [Ln L₃X_n(H₂O)_n] where Ln = Pr(III), Sm(III), Eu (III), Gd (III), Tb (III), Dy (III), X = Cl^?1, NO₃ ^?2, n = 2–7, and L is 1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1- thiosemicarbazone have been prepared. The lanthanide complexes (5) were derived from the reaction between 1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1-thiosemicarbazone (4) with an aqueous solution of lanthanide salt. Chalcone thiosemicarbazone ligand (4) was prepared by the reaction of [1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)]prop-2-enone (chalcone) (3) with thiosemicarbazide in the presence of hot ethanol. All the lanthanide-ligand 1:3 complexes have been isolated in the solid state, are stable in air, and characterized on the basis of their elemental and spectral data.

Thiosemicarbazone ligands behave as bidentate ligands by coordinating through the sulfur of the isocyanide group and nitrogen of the cyanide residue. The probable structure for all the lanthanide complexes is also proposed. The chalcone thiosemicarbazone ligands and their lanthanide complexes have been screened for their antifungal and antibacterial studies. Some of the synthesized lanthanide complexes have shown enhanced activity compared with that of the free ligand.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis,characterization and antibacterial studies of Tm(III), Yb(III) and Lu(III) complexes of morin

New solid amorphous compounds of Tm(III), Yb(III) and Lu(III) with morin have been synthesized. Their composition and some physicochemical properties have been studied by elemental analysis, thermogravimetric analysis, IR spectroscopy as well as by conductivity, UV/Vis, MS, and NMR spectroscopies in solution. The spectroscopic studies have indicated that the 3-OH hydroxyl group and the carbonyl oxygen of morin were involved in the coordination of metal ion. The antibacterial activity of the synthesized compounds has been determined by the cylinder-plate diffusion and dilution methods (determination of minimum inhibitory concentration).     

Syntheses and Crystal Structures of Di-, Tri- and Tetra-nuclear Cobalt(II)-Lanthanide(III) Carboxylate Complexes

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Solution Phase Chemistry of Lanthanide Complexes. 12. 1:1 and 1:2 Lanthanide Complexes with s-Carboxymethoxysuccinic Acid

Abstract

The solution phase coordination chemistry associated with 1:1 and 1:2 complexes of lanthanide ions with S-carboxymethoxysuccinic acid (CMOS) has been studied by spectroscopic means. The Tb(III) luminescence intensities and lifetimes were found to be sensitive towards the solution phase properties, as were the circularly polarized luminescence spectra of these complexes. It was found that below pH 6, Ln(CMOS) complexes were monomeric in nature and contained an average of 6 molecules of coordinated water. Above neutral pH, the Ln(CMOS)₂ complexes became self-associated into hydroxy-bridged, oligomeric species. The Ln(CMOS)₂ complexes were found to be oligomeric at all pH values, with ligand bridging taking place below neutral pH and hydroxy bridging taking place above neutral pH.     

Thermal decomposition of scandium(III) 2-chloro-, 30chloro, 4-chloro- and 2,4-dichlorobenzoates in an air atmosphere

The conditions of thermal decomposition of hydrated scandium(III) chlorobenzoates were studied. On heating, the carboxylates decompose in many steps. The hydrated complexes first lose water of crystallization in one or two steps and then anhydrous compounds are transformed to Sc₂O₃ with formation of Sc₂O(CO₃)₂ intermediate. The dehydration of the complexes is accompanied by an endothermic effect and the decomposition of anhydrous complexes by strong endothermic effects. The anhydrous complexes are melted at 255–300°C.