Solution and Thermodynamic Studies on Binary and Ternary Complexes of Lanthanides

The interactions of La(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Dy(Ⅲ), and Yb(Ⅲ) with cytosine, 5-bromocytosine, 5-azacytosine and 5-flurocytosine as primary ligands (L) and guanine (A) as secondary ligand for both binary (1:1) as well as ternary (1:1:1) systems were investigated by potentiometric equilibrium measurements at 25, 35 and 45 ℃ in aqueous solution (ionic strength, μ=0.1 mol·dm-3 NaNO3). The stability constants of the binary (1:1) and ternary (1:1:1) metal-ligand complexes follow the following order La＜Pr＜Nd＜Sm＜Eu＞Gd＜Dy＞Yb. Results also indicate that the ternary lanthanide complexes of La(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Dy(Ⅲ), and Yb(Ⅲ) are more stable than corresponding binary lanthanide complexes. The enthalpy (Δhof) and entropy (Δsof) changes for the formation of binary and ternary complexes were calculated from temperature coefficient data. The ΔΔSof values are positive for all the metal ligand systems. The negative ΔΔHof values indicate the extra stability of the ternary complexes by the exothermic enthalpy changes (ΔΔSof=ΔTSof-ΔBSof and ΔΔHof=ΔTHof-ΔBHof where ΔTSof, ΔTHof and ΔBSof, ΔBHof are the entropy and enthalpy values associated with the ternary and binary complexes, respectively). It was also proposed that the guanine is bonded to metal ions through N1/C6=O and N7 whereas cytosine and its derivatives are bonded through N3 atoms in ternary complexes.     

Chemical equilibrium constants of rare earth nitrates and tri-n-butyl phosphate complex formation

Mixed rare earth nitrates (REi(NO3)3) in the aqueous solution was mixed with tri-n-butyl phosphate (TBP, (n-C4H9O)3PO) dissolved in kerosene for the formation of their corresponding complexes (REi(NO3)3·ni(n-C4H9O)3PO) at 303 K. The effects of initial concentrations of both TBP and mixed rare earth nitrates on the equilibrium constants of their complex formations were investigated. The complexes were formed almost immediately after mixing. The simultaneous formations reached their chemical equilibria within a few minutes by shaking the mixture at 200 r/min. The chemical equilibrium constants of the complex formations were independent of the initial TBP concentrations. However, they were decreased by reducing the concentration of REi(NO3)3. All equilibrium constants of the simultaneous complex formations were less than 0.7, while the average molar ratio of TBP to REi(NO3)3 of the complexes varied between 1.0 and 1.6. The chemical equilibrium constant for the formation of La(NO3)3·(n-C4H9O)3PO was 0.09, while that of Dy(NO3)3·(n-C4H9O)3PO was 0.68. The ascending sequence of chemical equilibrium constants for the simultaneous formations was La, Ce, Pr, Nd, Eu, Y, Sm, Gd, and Dy.     

Synthesis, spectroscopic characterization, and thermal decomposition kinetics of some lanthanide(Ⅲ) nitrate complexes of 2-(N-o-hydroxyacetophenone) amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Complexes of La(Ⅲ), Ce(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Dy(Ⅲ), Yb(Ⅲ), and Lu(Ⅲ) with 2-(N-o- hydroxyacetophenone)amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene (HAAT) formed by the condensation of o-hydroxyacetophenone and 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene were synthesized and characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility data, UV-Visible, IR, and NMR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate coordinating to the metal ion through ONO donor sequence. A coordination number nine was proposed for the complexes. Thermal decomposition studies of the ligand and lanthanum(Ⅲ) complex were carried out and kinetic parameters were calculated using Coats-Redfern equation. The decomposition reactions followed random nucleation mechanism with one nucleus on each particle.     

Synthesis,spectroscopic characterization,DNA cleavage and antibacterial studies of a novel tridentate Schiff base and some lanthanide（III） complexes

A novel potential tridentate Schiff base was prepared by condensing equimolar quantities of 2-hydroxyacetophenone and 2-aminopyrimidine in methanol. This ligand was versatile in forming a series of complexes with lanthanide ions such as La（III）, Pr（III）, Nd（III）, Sm（III）, Gd（III）, Dy（III） and Yb（III）. The ligand and the metal complexes were characterized through elemental analysis, molar conductance, UV-Visible, IR, 1H NMR, and mass spectral studies. The spectral studies indicated that the ligand was coordinated to the metal ion in neutral tridentate fashion through the azomethine nitrogen, one of the nitrogen atoms in the pyrimidine ring and the phenolic oxygen without deprotonation. Thermal decomposition and luminescence property of lanthanum（III） complex were also examined. The X-ray diffraction patterns showed the crystalline nature of the ligand and its lanthanum（III） complex. The DNA cleavage studies of the ligand and the metal complexes were carried out and it was observed that the lanthanum（III） and neo-dymium（III） complexes cleaved the pUC19 DNA effectively. The ligand and the metal complexes were screened for their antibacte-rial activities. The metal complexes were found to be more potent bactericides than the ligand.     

Synthesis,spectroscopic characterization,and thermal decomposition kinetics of some lanthanide（Ⅲ） nitrate complexes of 2-（N-o-hydroxyacetophenone） amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Complexes of La（Ⅲ）, Ce（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, Gd（Ⅲ）, Dy（Ⅲ）, Yb（Ⅲ）, and Lu0ID with 2-（N-o- hydroxyacetophenone）amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene （HAAT） formed by the condensation of o-hydroxyacetophenone and 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene were synthesized and characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility data, UV-Visible, IR, and NMR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate coordinating to the metal ion through ONO donor sequence. A coordination number nine was proposed for the complexes. Thermal decomposition studies of the ligand and lanthanum（Ⅲ） complex were carried out and kinetic parameters were calculated using Coats-Redfem equation. The decomposition reactions followed random nucleation mechanism with one nucleus on each particle.     

Microwave assisted synthesis,spectroscopic, thermal,and antifungal studies of some lanthanide（Ⅲ） complexes with a heterocyclic bishydrazone

A bishydrazone formed by the condensation of isatinmonohydrazone and salicylaldehyde reacted with lanthanide（Ⅲ） chloride to form complexes of the type [Ln（HISA）2Cl3], where, Ln=La（Ⅲ）, Ce（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, or Gd（Ⅲ） and HISA= [（2-hydroxybenzaldehyde）-3-isatin]bishydrazone. Both reactions were carried out under microwave conditions. The ligand and the metal complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, UV visible, infrared, far infrared, and proton NMR spectral data. The ligand acted as neutral tridentate, coordinating through the carbonyl oxygen, azomethine nitrogen, and phenolic oxygen without deprotonation. The ligand and lanthanum（Ⅲ） complex were subjected to X-ray diffraction studies. The X-ray diffraction pattern of ligand exhibited its crystalline nature and that of the lanthanum（Ⅲ） complex indicated its amorphous character. The thermal decomposition behaviour of the complex, [La（HISA）2Cl3], was examined in the temperature range of 40-800 ℃ using TG, DTG, and DTA. The ligand and the metal complexes were screened for their antifungal activities.     

Thermochemical Properties of the Complexes RE(HSal)3·2H2O (RE=La, Ce, Pr, Nd, Sm)

Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(Hsal)3·2H2O(RE=La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE3 ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, ΔcU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated.     

Synergistic extraction of rare earths by mixture of HDEHP and HEH/EHP in sulfuric acid medium

The extraction of RE（Ⅲ） （RE=La, Nd, Sm, Gd） in sulfuric acid medium using the mixture of HDEHP（H2B2） and HEH/EHP（H2L2） was investigated. The synergistic enhancement coefficient（R） was calculated for La （1.96）, Nd（3.52）, Sm（5.96）, and Gd（5.71）, respectively, at pH=2.0, and it was seen that the R increased with the increase of aqueous quilibrium pH. The configuration of the extracted complexes was considered to be RE（SOa）xH2x（HB2）3 with HDEHP, RE（SOa）xH2x（HL2）3 with HEH/EHP, and RE（HB2）2（HL2） with their mixture as the extractant with the slope method. The equilibrium constants and stability constants were calculated. A cation exchange mechanism was proposed as well.     

Synthesis and spectral characteristics of La2MoO6：Ln3＋ （Ln=Eu, Sm, Dy, Pr, Tb） polycrystals

The novel phosphors of La 2 MoO 6 activated with the trivalent rare earth Ln 3+ (Ln=Eu, Sm, Dy, Pr, Tb) ions were synthesized by solid state reactions at high temperature in air atmosphere, and their phase impurities and luminescent properties were studied. The photoluminescence (PL) excitation and emission spectra, and decay curves were employed to study their luminescence properties. The lifetimes of the characteristic emissions from Ln 3+ ions were in the order of millisecond except Pr 3+ ions. (LaEu 1-x ) 2 MoO 6 was a promising phosphor for practical application and the optimum concentration was x=0.075. The concentration quenching mechanism of Eu 3+ was also discussed by theoretical fitting using Burshtein model.     

New luminescent 10-oxybenzoquinolate complexes of rare earth metals

A series of Sc,Y,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Ho,Er,Tm and Yb complexes with oxybenzoquinoline ligands(BQ) was synthesized by the reactions of 10-hydroxybenzo[h]quinoline with cyclopentadienides or tris(trimethylsilyl)amides of rare earth metals.The structure,as well as the photo-and electroluminescent(PL,EL) properties of these complexes in solutions and solid state were studied.In solutions,complexes of sodium and lanthanides exhibit double peaked ligand-centered PL of enol and keto forms of BQ with a...     

Synthesis and fluorescence properties of Eu（Ⅲ）, Tb（Ⅲ） and Sm（Ⅲ） with β-diketone and 2,2＇- bipyridine

Three new rare earth ternary complexes,RE(PPP)3bpy(RE=Sm 3+ ,Eu 3+ ,Tb 3+ ),were synthesized by the reaction of 1-phenyl-3-(p-phenylethynylphenyl)-1,3-propanedione(HPPP)and 2,2′-bipyridine(bpy)with rare earth chloride RECl3,respectively,in alcohol solution. The compositions were characterized by means of infrared(IR)spectra,chemical analysis,elemental analysis,and thermodynamic analysis.Luminescent properties of the three complexes were studied.At room temperature,under UV light excitation,the Sm 3+ ,Eu 3+ and Tb 3+ complexes exhibited characteristic emission of the central ions.The fluorescence spectra showed that the fluorescence emission intensity of Eu 3+ complex was the strongest.The narrow strongest emission band of Eu 3+ complex was considered to be a valuable material with bright red fluorescence.     

Physico-chemical properties of 3-methoxy-2-nitrobenzoates of some rare earth elements（Ⅲ）

The complexes of 3-methoxy-2-nitrobenzoates of Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Er(III) and Tm(III) with the formula: Ln(C8H6NO5)3·2H2O, where Ln=lanthanides(III), were synthesized and characterized by elemental analysis, Forier transform irtrared (FTIR) spectroscopy, magnetic and thermogravimetric studies and also by X-ray diffraction (XRD) measurements. The complexes had col- ours typical for Ln(III) ions. The carboxylate groups bound as bidentate chelating. On heating to 1173 K in air they decomposed in the same way, at first, dehydrated in one step to anhydrous salts, and then decomposed to the oxides of respective metals with intermediate formation of the oxycarbonates. The enthalpy values of the dehydration process changed from 133.72 to 44.50 kJ/mol. Their solubility in water at 293 K was of the order of 10-4 mol/dm3. The magnetic moments of analysed complexes were determined by Gouy’s method in the range of 76-303 K.     

Measurements of Enthalpy Change of Reaction of Formation, Molar Heat Capacity and Constant-Volume Combustion Energy of Solid Complex Yb（Et2dtc）3（phen）

A ternary solid complex Yb(Et2dtc)3(phen) was obtained from the reaction of hydrous ytterbium chloride with sodium diethyldithiocarbamate (NaEt2dtc), and 1, 10-phenanthroline (o-phen·H2O) in absolute ethanol.The bonding characteristics of the complex were characterized by IR.The result shows Yb3 bands with two sulfur atoms in the Na(Et2dtc)3 and two nitrogen atoms in the o-phen.The enthalpy change of liquid-phase reaction of formation of the complex ΔrHθm (l), was determined as being (-24.838±0.114) kJ·mol-1 at 298.15 K, by an RD-496 Ⅲ type heat conduction microcalormeter.The enthalpy change of the solid-phase reaction of formation of the complex ΔrHθm (s), was calculated as being (108.015±0.479) kJ·mol-1 on the basis of an appropriate thermochemistry cycle.The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature during the liquid-phase reaction.Fundamental parameters, the activation enthalpy, ΔHθ≠, the activation entropy, ΔSθ≠, the activation free energy, ΔGθ≠, the apparent reaction rate constant k, the apparent activation energy E, the pre-exponential constant A, and the reaction order n, were obtained by a combination of the reaction thermodynamic and kinetic equations with the data from the thermokinetic experiments.At the same time, the molar heat capacity of the complex cm, p, was determined to be (86.34±1.74) J·mol-1·K-1 by the same microcalormeter.The constant-volume combustion energy of the complex, ΔcU, was determined to be (-17954.08±8.11) kJ·mol-1 by an RBC-Ⅱ type rotating-bomb calorimeter at 298.15 K.Its standard enthalpy of combustion, ΔcHθm, and standard enthalpy of formation, ΔfHθm, were calculated to be (-17973.29±8.11) kJ·mol-1 and (-770.36±9.02) kJ·mol-1, respectively.     

Synthesis, characterization and properties of some rare earth complexes with 2,6-pyridine dicarboxylic acid and α-Picolinic acid

Five novel ternary complexes were synthesized by the rare earth with 2,6-pyridine dicarboxylic acid andα-picolinic acid.These complexes were characterized by elemental analysis,molar conductivity,FT-IR,UV-Vis,Raman,TG-DTA and XRD.The general formula of the complexes was[RE(DPA)(L α )(H2O)]·2H2O(RE=Pr 3+ ,Nd 3+ ,Sm 3+ ,Eu,Er 3+ ;DPA=2,6-pyridine dicarboxylic acid;L α =α-picolinic acid). The investigation of fluorescence properties of the Eu-complex showed that the Eu(III)ion could be sensitized efficiently by the ligand to some extent.The antibacterial activity test indicated that all the five complexes exhibited antibacterial ability against Escherichia coli and Staphylococcus aureus with broad antimicrobial spectrums.     

Facile sol-gel combustion synthesis and photoluminescence enhancement of CaZrO3：Sm3＋ nanophosphors via Gd3＋ doping

CaZrO3:Sm and CaZrO3:Sm,Gd nanophosphors were synthesized by a facile and efficient sol-gel combustion method. Their structure and optical properties were studied. The photoluminesce (PL) results showed that the phosphor could be efficiently excited by irradiation at wavelengths in the visible light region (350-430nm). The CaZrO3:Sm nanophosphor exhibited strong yellow-green, orange and red emissions with peak wavelength centered at 565nm (4G5/2→6H5/2), 601nm (4G5/2→6H7/2) and 645nm (4G5/2→6H9/2), respectively. The incorporation of Gd3+ ions could greatly improve the luminescence intensity. The highest emission intensity was observed with 2mol.% Gd3+ doped CaZrO3:3mol.% Sm powder. The material had potential application in the development of materials for LED’s and other optical devices in the visible region.     

Lanthanide amino acid Schiff base complexes： synthesis, spectroscopic characterization, physical properties and in vitro antimicrobial studies

Complexes of La(Ⅲ),Nd(Ⅲ),Gd(Ⅲ),Sm(Ⅲ),and Ce(Ⅳ) were synthesized with Schiff base [(3,5-di-tert-butyl-2-hydroxybenzyl) amino] acetic acid(H 3 L).The ligand and its complexes were synthesized and characterized based on the following analysis:elemental analyses,FAB-mass,molar conductance measurements,magnetic measurement,UV-visible,IR,and NMR spectral studies.The spectral data revealed that the ligand acted as a neutral tridentate coordinating to metal ion through ONO donor sequence.Thermal degradation studies of the ligand and its complexes showed that the previous lanthanide complexes were more thermally stable than the ligand itself.The Schiff base and its complexes were screened for their antibacterial(Escherichia coli,Staphylococcus aureus) and antifungal(Aspergillus flavus and Candida Albicans).     

Energy transfer and luminescent properties of Pr^3＋ and/or Dy^3＋ doped NaYF4 and NaGdF4

The phosphors that are able to convert vacuum ultraviolet（VUV） light into visible light are demanded for the development of novel displaying and lighting devices.NaYF4：Pr3＋,Dy3＋,NaGdF4：Pr3＋,NaGdF4：Dy3＋and NaGdF4：Pr3＋,Dy3＋were prepared by hydrothermal synthesis method and their luminescent properties in VUV-vis spectral region were investigated at room temperature.For NaYF4：Pr3＋,Dy3＋,no energy transfer process from Pr3＋to Dy3＋was observed.However,the introduction of Gd3＋into the fluoride lattice led to intense Dy3＋emissions upon Pr3＋4f5d state excitation.Gd3＋acted as an intermediate,resulting in efficient energy transfer from Pr3＋to Dy3＋in NaGdF4.Pr3＋transferred most of its energy to Gd3＋,and then the energy was transferred from Gd3＋to Dy3＋.So NaGdF4：Pr3＋,Dy3＋not only took full advantage of the intense Pr3＋4f5d absorption,but converted the VUV excitation light into the near-white emission of Dy3＋.     

Calorimetric Titration of Complexation of the N-benzylmonoaza-18-Crown-6 with Rare Earth(Ⅲ)Nitrates in Anhydrous Acetonitrile

Calorimetric titrations were performed in anhydrous acetonitrile at 298.15 K,giving the com-plex stability constants(K_s)and the thermodynamic parameters for the complexation of the rare earth ni-trates(La～Er,Yb)with N-benzylmonoaza-18-crown-6(18-C-6).Thermodynamic quantities clearly in-dicate that the coordination stability of the arm-type 18-crown-6 with the lanthanoid nitrates increasesfrom Ce to Gd,and decreases slightly from Gd to Tb with increasing atomic number.The coordination of thearm-type 18-C-6 with Gd shows the stonger complexation ability and selectivity.Thermodynamically theformation of the complexes is evidently driven by enthalpy,but the complexes stability sequence is essentiallyentropy governed.     

Microwave assisted synthesis, spectroscopic, thermal, and antifungal studies of some lanthanide(Ⅲ) complexes with a heterocyclic bishydrazone

A bishydrazone formed by the condensation of isatinmonohydrazone and salicylaldehyde reacted with lanthanide(Ⅲ) chloride to form complexes of the type [Ln(HISA)2Cl3], where, Ln=La(Ⅲ), ce(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sin(Ⅲ), Eu(Ⅲ), or Gd(Ⅲ) and HISA=[(2-hydroxybenzaldehyde)-3-isatin]bishydrazone. Both reactions were carried out under microwave conditions. The ligand and the metal complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, UV visible, infrared, far infrared, and proton NMR spectral data. The ligand acted as neutral tridentate, coordinating through the carbonyl oxygen, azomethine nitrogen, and phenolic oxygen without deprotonation. The ligand and lanthanum(Ⅲ) complex were subjected to X-ray diffraction studies. The X-ray diffraction pattern of ligand exhibited its crystalline nature and that of the lanthanum(Ⅲ) complex indicated its amorphous character. The thermal decomposition behaviour of the complex, [La(HISA)2Cl3], was examined in the temperature range of 40-800 ℃ using TG, DTG, and DTA. The ligand and the metal complexes were screened for their antifungal activities.     

Energy transfer between Gd^3＋ and Tb^3＋ in phosphate glass

The phosphate glass doped with Gd3+,Tb3+ and Gd3+/Tb3+ were prepared by high temperature melting.The photo-luminescence behavior of Gd3+ and Tb3+ in phosphate glass were investigated by absorption,excitation,and emission spectroscopy.Energy transfer between Gd3+ and Tb3+ in phosphate glass was studied,and it was found that there were two energy transfer mechanisms between Gd3+ and Tb3+ in phosphate glass: one was from 4f7 level of Gd3+ to the 4f8 level of Tb3+,and the other was from 5d level of Tb3+ to 4f7 level of Gd3+.The new findings would be beneficial for the study of Tb3+-doped scintillating phosphate glass.