Complexation and the laser luminescence studies of Eu(III), Am(III), and Cm(III) with EDTA,CDTA, and PDTA and their ternary complexation with dicarboxylates

Spectroscopy has been used to determine the number of coordinated water molecules bound to Eu(III) and Cm(III) in a series of binary complexes of polyaminocarboxylate and their ternary complexes with dicarboxylates as well as with similar ligands with additional O-, N-, and S-donors. Complexes of Eu(III) and Cm(III) with polyaminocarboxylate alone contain ca. 2.5–3.0 waters of hydration. Increasing the steric requirement of a polyaminocarboxylate by increasing the number of groups in the ligand backbone does not appreciably change the hydration of these cations. The stability constants of the binary and ternary complexes of Cm(III), Am(III), and Eu(III) with these ligands were measured by solvent extraction in a solution of 0.1 M (NaClO₄). The size, basicity, specific M³⁺-second ligand interactions, and steric requirement of the ligands are the factors which affect the ternary complexation. Knowledge of the chemical species formed by actinide cations with organic ligands (carboxylates and aminocarboxylates), which are present in all nuclear waste, is important to understand the behavior of waste forms and the migration behavior of actinides in the environment.     

Complexation of Eu(III), Am(III) and Cm(III) with Dicarboxylates: Thermodynamics and Structural Aspects of the Binary and Ternary Complexes

The complexation of Eu(III), Am(III) and Cm(III) with dicarboxylate anions with O, N or S donor groups was measured in I=6.60 mol⋅kg⁻¹ (NaClO₄) at temperatures of 0–60 °C by potentiometry and solvent extraction. The complexation thermodynamics of these complexes show that their stability is due to highly favorable complexation entropies because the complexation enthalpies are endothermic. Luminescence studies with Eu(III) and Cm(III) were used to measure the hydration numbers of the complexes. NMR spectra of ¹H and ¹³C were used to determine the binding modes of La(III) with the ligands. The formation of 1:1:1 ternary complexes of M(EDTA)⁻ with the dicarboxylate ligands was studied to determine changes in coordination of the metal cation with formation of the ternary species. The complexation of ternary complexes changes from bidentate to monodentate as the chain length between the binding sites of the dicarboxylates increases from 1 (malonate) to 4 (adipate). DFT computations were used to confirm the structural aspects of the interaction of these complexes.     

Adsorption of Eu(III) on titanate nanotubes studied by a combination of batch and EXAFS technique

The effects of pH,contact time and natural organic ligands on radionuclide Eu(Ⅲ) adsorption and mechanism on titanate nanotubes(TNTs) are studied by a combination of batch and extended X-ray absorption fine structure(EXAFS) techniques.Macroscopic measurements show that the adsorption is ionic strength dependent at pH < 6.0,but ionic strength independent at pH > 6.0.The presence of humic acid(HA) /fulvic acid(FA) increases Eu(Ⅲ) adsorption on TNTs at low pH,but reduces Eu(Ⅲ) adsorption at high pH.The results of EXAFS analysis indicate that Eu(Ⅲ) adsorption on TNTs is dominated by outer-sphere surface complexation at pH < 6.0,whereas by inner-sphere surface complexation at pH > 6.0.At pH < 6.0,Eu(Ⅲ) consists of ～ 9 O atoms at REu?O ≈ 2.40  in the first coordination sphere,and a decrease in NEu-O with increasing pH indicates the introduction of more asymmetry in the first sphere of adsorbed Eu(Ⅲ).At long contact time or high pH values,the Eu(Ⅲ) consists of ～2 Eu at REu-Eu ≈ 3.60  and ～ 1 Ti at REu-Ti ≈ 4.40 ,indicating the formation of inner-sphere surface complexation,surface precipitation or surface polymers.Surface adsorbed HA/FA on TNTs modifies the species of adsorbed Eu(Ⅲ) as well as the local atomic structures of adsorbed Eu(Ⅲ) on HA/FA-TNT hybrids.Adsorbed Eu(Ⅲ) on HA/FA-TNT hybrids forms both ligand-bridging ternary surface complexes(Eu-HA/FA-TNTs) as well as surface complexes in which Eu(Ⅲ) remains directly bound to TNT surface hydroxyl groups(i.e.,binary Eu-TNTs or Eu-bridging ternary surface complexes(HA/FA-Eu-TNTs)).The findings in this work are important to describe Eu(Ⅲ) interaction with nanomaterials at molecular level and will help to improve the understanding of Eu(Ⅲ) physicochemical behavior in the natural environment.     

Intensity-tunable micelles and films containing bimetal ions—europium(III) and terbium(III)

In this paper, multicolored micelles were prepared by coordination of lanthanide(III) (europium(III) (Eu(III)) and terbium(III) (Tb(III))) ions with block copolymer in different molar ratios of n _Eu(III)/n _Tb(III). The micelles formed by polymer–Eu(III)/Tb(III) could emit higher quantum yield luminescence than the mixture of polymer–Eu(III) micelles and polymer–Tb(III) micelles. The micelles containing Eu(III) and Tb(III) could emit a yellow-green color, and the intensity varied with the molar ratios of n _Eu(III)/n _Tb(III). In the constant concentrations of Eu(III) and 1,10-phenanthroline (Phen), the intensity of ⁵D₀→⁷F₂ increased with the addition of Tb(III), and the intensity of ⁵D₄→⁷F₅ decreased with the increasing of Eu(III) in the constant concentrations of Tb(III) and Phen. All the multicolored micelles could be spin-coated as intensity-tunable films.     

Synthesis and photophysical properties of new Ln(III) (Ln = Eu(III), Gd(III), or Tb(III)) complexes of 1-amidino-O-methylurea

Three new solid lanthanide(III) complexes, [Ln(1-AMUH)₃] · (NO₃)₃ (1-AMUH = 1-amidino-O-methylurea; Ln = Eu(III), Gd(III), or Tb(III)) were synthesised and characterised by elemental analysis, infrared spectra, magnetic moment measurement, and electron paramagnetic resonance (EPR) spectra for Gd(III) complex. The formation of lanthanide(III) complexes is confirmed by the spectroscopic studies. The photophysical properties of Gd(III), Eu(III), and Tb(III) complexes in solid state were investigated. The Tb(III) complex exhibits the strongest green emission at 543 nm and the Eu(III) complex shows a red emission at 615 nm while the Gd(III) complex shows a weak emission band at 303 nm. Under excitation with UV light, these complexes exhibited an emission characteristic of central metal ions. The powder EPR spectrum of the Gd(III) complex at 300 K exhibits a single broad band with g = 2.025. The bi-exponential nature of the decay lifetime curve is observed in the Eu(III) and Tb(III) complexes. The results reveal them to have potential as luminescent materials.     

Thermodynamics of Cm(III) in Concentrated Salt Solutions: Carbonate Complexation in NaCl Solution at 25°C

The carbonate complexation reactions of Cm(III) were studied by time-resolved laser fluorescence spectroscopy in 0–6 m NaCl at 25°C. The ionic strength dependence of the stepwise formation constants for the carbonato complexes Cm(CO₃) _n ^3–2n with n = 1, 2, 3, and 4 is described by modeling the activity coefficients of the Cm(III) species with Pitzer's ion-interaction approach. Based on the present results and literature data for Cm(III) and Am (III), the mean carbonate complexation constants at I = 0 are calculated to be: log ₁₀₁ ^o =8.1 ±0.3, log ₁₀₂ ^o =13.0 ± 0.6, log ₁₀₃ ^o =15.2 ± 0.4, and log ₁₀₄ ^o =13.0 ± 0.5. Combining these equilibrium constants at infinite dilution and the evaluated set of Pitzer parameters, a model is obtained, that reliably predicts the thermodynamics of bivalent actinide An(III) carbonate complexation in dilute to concentrated NaCl solution.     

Anionically Substituted 1,1′,1″‐Methylidynetris[1H‐pyrazole] Ligands for the Formation of Neutral Lanthanide Complexes in Water: Synthesis,Characterization, and Photophysical Properties

The six‐step synthesis of the new podand‐type ligand 6,6′,6″‐[methylidenetri(1H‐pyrazole‐1,3‐diyl)]tris[pyridine‐2‐carboxylic acid] (LH₃) is described. Reaction of LH₃ with LnCl₃ ?6 H₂O (Ln=Eu, Gd, Tb) in MeOH resulted in the isolation of [LnL]?HCl complexes characterized by elemental analysis, mass and IR spectroscopy. Photophysical studies of the Eu and Tb complexes in aqueous solutions revealed the characteristic luminescence features of the metal atoms, indicative of an efficient ligand‐to‐metal energy‐transfer process. Determination of the luminescence quantum yields in H₂O showed the Tb complex to be highly luminescent (?=15%), while, for the Eu complex, the quantum efficiency was only 2%. Excited‐state‐lifetime measurements in H₂O and D₂O evidenced the presence of ca. three H₂O molecules in the first coordination sphere of the complexes. Investigation of the Gd complex allowed the determination of the ligand‐centered triplet state and showed the ligand to be well suited for energy transfer to the metal. The luminescence properties of the complexes are described, and the properties of the ligand as a suitable complexation pocket is questioned.     

Complexation studies of Cm(III), Am(III), and Eu(III) with linear and cyclic carboxylates and polyaminocarboxylates

Solvent extraction and potentiometric titration methods have been used to measure the stability constants of Cm(III), Am(III), and Eu(III) with both linear and cyclic carboxylates and polyaminocarboxylates in an ionic strength of 0.1?mol?L^?1 (NaClO₄). Luminescence lifetime measurements of Cm(III) and Eu(III) were used to study the change in hydration upon complexation over a range of concentrations and pH values. Aromatic carboxylates, phthalate (1,2 benzene dicarboxylates, PHA), trimesate (1,3,5 benzene tricarboxylates, TSA), pyromellitate (1,2,4,5 tetracarboxylates, PMA), hemimellitate (1,2,3 benzene tricarboxylates, HMA), and trimellitate (1,2,4 benzene tricarboxylates, TMA) form only 1?:?1 complexes, while both 1?:?1 and 1?:?2 complexes were observed with PHA. Their complexation strength follows the order: PHA～TSA>TMA>PMA>HMA. Carboxylate ligands with adjacent carboxylate groups are bidentate and replace two water molecules upon complexation, while TSA displaces 1.5 water molecules of hydration upon complexation. Only 1?:?1 complexes were observed with the macrocyclic dicarboxylates 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N′-diacetate (K21DA) and 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N′-diacetate (K22DA); both 1?:?1 and 1?:?2 complexes were observed with methyleneiminodiacetate (MIDA), hydroxyethyleneiminodiacetate (HIDA), benzene-1,2-bis oxyacetate (BDODA), and ethylenediaminediacetate (EDDA), while three complexes (1?:?1, 1?:?2, and 1?:?3) were observed with pyridine 2,6 dicarboxylates (DPA) and chelidamate (CA). The complexes of M-MIDA are tridentate, while that of M-HIDA is tetradentate in both 1?:?1 and 1?:?2 complexes. The M-BDODA and M-EDDA complexes are tetradentate in the 1?:?1 and bidentate in the 1?:?2 complexes. The complexes of M-K22DA are octadentate with one water molecule of hydration, while that of K21DA is heptadentate with two water molecules of hydration. Simple polyaminocarboxylate 1,2 diaminopropanetetraacetate (PDTA) and ethylenediamine N,N′-diacetic-N,N′-dipropionate (ENDADP) like ethylenediaminetetraacetate (EDTA) form only 1?:?1 complexes and their complexes are hexadentate. Polyaminocarboxylates with additional functional groups in the ligand backbone, e.g., ethylenebis(oxyethylenenitrilo) tetraacetate (EGTA), and 1,6 diaminohexanetetraacetate (HDTA) or with additional number of groups in the carboxylate arms diethylenetriamine pentaacetato-monoamide (DTPA-MA), diethylenetriamine pentaacetato-bis-methoxyethylamide (DTPA-BMEA), and diethylenetriamine pentaacetato-bis glucosaamide (DTPA-BGAM) are octadentate with one water molecule of hydration, except N-methyl MS-325 which is heptadentate with two water molecules of hydration and HDTA which is probably dimeric with three water molecules of hydration. Macrocyclic tetraaminocarboxylate, 1,4,7,10-tetraazacyclododecanetetraacetate (DOTA) forms only 1?:?1 complex which is octadentate with one water molecule of hydration. The functionalization of these carboxylates and polycarboxylates affect the complexation ability toward metal cations. The results, in conjunction with previous results on the Eu(III) complexes, provide insight into the relation between ligand steric requirement and the hydration state of the Cm(III) and Eu(III) complexes in solution. The data are discussed in terms of ionic radii of the metal cations, cavity size, basicity, and ligand steric effects upon complexation.     

3-Picoline-N-oxide complexes of rare-earth bromides

3-Picoline-N-oxide (3-PicNO) complexes of rare-earth bromides of the formulaMBr₃(3-PicNO)_8–n·nH₂O wheren=0 forM=La, Pr, Nd, Sm Tb or Y andn=2 forM=Ho or Yb have been prepared. Infrared and proton NMR studies indicate that the coordination of the ligand is through oxygen. Conductance data in acetonitrile suggest that two bromide ions are coordinated to the metal ion. Proton NMR studies suggest a bicapped dodecahedral arrangement of the ligands around the metal ion in solution for Pr(III), Nd(III) and Tb(III) complexes.     

Thermal behavior and other properties of Pr(III), Sm(III), Eu(III), Gd(III), Tb(III) complexes with 4,4′-bipyridine and trichloroacetates

A novel mixed-ligand complexes with empirical formulae: Ln(4-bpy)_1.5(CCl₃COO)₃·nH₂O (where Ln(III) = Pr, Sm, Eu, Gd, Tb; n = 1 for Pr, Sm, Eu and n = 3 for Gd, Tb; 4-bpy = 4,4′-bipyridine) were prepared and characterized by chemical, elemental analysis and IR spectroscopy. Conductivity studies (in methanol, dimethylformamide and dimethylsulfoxide) were also described. All complexes are crystalline. The way of metal–ligand coordination was discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Pr₆O₁₁, Ln₂O₃ (for Sm, Eu, Gd) and Tb₄O₇. TG-MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Pr(III) and Sm(III) compounds in air.     

New heteroleptic lanthanide complexes as multimodal drugs: Cytotoxicity studies,apoptosis, cell cycle analysis,DNA interactions,and protein binding

We report herein the synthesis and characterization of four new heteroleptic complexes of Sm(III), Eu(III), Gd(III), and Tb(III) with the natural flavonoid 5‐hydroxyflavone (primuletin) and 1,10‐phenanthroline. According to the physicochemical characterization, the mononuclear complexes correspond to the general formula [Ln(OH) ₂ L ₁ L ₂ ]·nH ₂ O , where L₁ = C₁₅H₉O₃ (deprotonated 5‐hydroxyflavone) and L₂ = C₁₂H₈N₂ (1,10‐phenanthroline), Ln is the lanthanide cation, and n = 4 for Sm(III), 3.5 for Eu(III), 2 for Gd(III), and 3 for Tb(III). A six‐coordinated distorted octahedron geometry was proposed for the complexes, and density functional theory (DFT) studies were used to calculate their optimized geometry. Cytotoxicity was studied using MTS assay on cervical, colorectal, colon, breast, and ovarian adenocarcinoma cell lines. Flow cytometry data were consistent with apoptotic cell death and disruption of the cell cycle in cervical and colon cancer cells. As a means to investigate the mechanism underlying the cytotoxic effects, the abilities of the complexes to interact with calf thymus DNA, human serum albumin, and transferrin have also been assessed. According to experimental and computational studies, the four lanthanide complexes act as DNA intercalators and bind strongly to serum proteins.     

Assembly, crystal structure, and luminescent properties of three-dimensional (10,3)-a netted rare earth coordination polymers

Solid complexes [REL(NO3)3]n with novel (10,3)-a type three-dimensional networks structure have been assembled using rare earth nitrates and an amide type semirigid tripodal bridging ligand, 1,3,5-tris {[(2′-benzylaminoformyl)phenoxyl]methyl}benzene (L), as building blocks. The complexes were crys- tallized in the orthorhombic system with chiral space group P212121. The whole structure consists of an infinite array of trigonal RE(III) ions bridged by tridentate ligands, and a novel (10,3)-a net is formed, which is very uncommon in the rare earth complexes. At room temperature, the Sm(III), Eu(III), Tb(III), Dy(III) complexes all exhibited characteristic luminescence emissions of central metal ions under UV light excitation.     

Competitive sorption of Cu(II) and Eu(III) ions on olive-cake carbon in aqueous solutions—a potentiometric study

The competitive sorption of Cu(II) and Eu(III) ions from aqueous solutions by olive-cake carbon, has been investigated by potentiometry at pH 6, I=0.1 M NaClO₄, 25°C and under normal atmospheric conditions. Evaluation of the experimental data supports the formation of inner-sphere surface complexes and results in the calculation of the formation constant of the surface complexes ((=S–O)₂Cu), which is found to amount log β _Cu=5.3±0.3. Addition of competing Eu(III) ions in the aqueous system leads to replacement of the Cu(II) by the competitor metal ion. Evaluation of the potentiometric data obtained from competition experiments indicates an ion-exchange mechanism. The formation constant of the Eu(III) species sorbed on olive cake carbon is found to be log β _Eu=5.1±0.5. Comparison of the complex formation constants of the olive-cake carbon with the corresponding complex formation constants for of olive cake and humic acid with the two metal ions, indicates that the same type of active sites is responsible for the metal ion complexation on the surface of the different types natural organic matter (e.g. olive-cake carbon, olive-cake and humic acid).     

Structures and luminescent properties of two heterotrimetallic Ln(III)–Sr(II)–K(I) complexes

Eu(III)–Sr(II)–K(I) and Tb(III)–Sr(II)–K(I) heterotrimetallic metal-organic frameworks with 2,4,6-pyridinetricarboxylic acid have been synthesized under hydrothermal conditions. The complexes are isomorphic and both in triclinic space group P-1. The ligands bond with three metal ions with two coordination modes. One connects seven metal ions and the other connects eight metal ions. IR spectra, thermal analysis, and photoluminescent properties have been studied. The results display strong characteristic emissions of Eu(III) or Tb(III) ions with excitation of ultraviolet radiation.     

Synthesis of several new lanthanide Glimepiride complexes for evaluation of microbial activity

The complexation between lanthanide metal ions like Nd(III), Tb(III), and Er(III) with Glimepiride produces 1: 1 molar ratio (metal: Glimepiride) monodentate complexes of general formula: [M(GMP)(H₂O)₄]Cl₃·xH₂O, where: M = Nd, Tb, and Er, x = 1, 10, respectively. The structures of obtained compounds were assigned by IR, ¹H NMR and UV/Vis spectra. Themogravimetric analysis and kinetic thermodynamic parameters have proved the thermal stability of Glimepiride complexes. Obtained lanthanide complexes showed significant effect against some bacteria and fungi.     

Complexes of Heavy Lanthanides and Yttrium with 3,4-dimethoxybenzoic Acid

The complexes of yttrium and heavy lanthanides with 3,4-dimethoxybenzoic acid of the formula: Ln(C₉ H₉ O₄ )₃ ×n H₂ O, where Ln =Y(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III) and Lu(III), and n =4 for Tb(III), Dy(III), n =3 for Ho(III), and n =0 for Er(III), Tm(III), Yb(III), Lu(III) and Y(III) have been prepared and characterized by elemental analysis, IR spectroscopy, thermogravimetric and magnetic studies and X-ray diffraction measurements. The complexes have colours typical of Ln³⁺ ions (Ho - cream, Tb, Dy, Yb, Lu, Y - white, Er - salmon). The carboxylate group in these complexes is a symmetrical, bidentate, chelating ligand. They are crystalline compounds characterized by various symmetry. On heating in air to 1273 K the hydrated 3,4-dimethoxybenzoates decompose in two steps while those of anhydrous only in one stage. The tetrahydrates of Tb and Dy and trihydrate of Ho 3,4-dimethoxybenzoates are firstly dehydrated to form anhydrous salts that next are decomposed to the oxides of the respective metals. The complexes of Er, Tm, Yb, Lu and Y are directly decomposed to the oxides of the appropriate elements. The solubility in water at 293 K for yttrium and heavy lanthanides is in the order of 10^-4 -10^-3 mol dm^-3 . The magnetic moments of the complexes were determined over the range 77–298 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and van Vleck. The results show that there is no influence of the ligand field on 4f electrons of lanthanide ions in these polycrystalline compounds and 4f electrons do not take part in the formation of M-O bonding. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Novel Architecture of a Heptadentate Macroacyclic 2,6-Bis [(3-methoxy salicylidene) Hydrazino carbonyl] Pyridine Towards Lanthanides: A Synthetic and Structural Studies of Dinuclear Lanthanide (III) Complexes

Reaction of Ln(NO₃)₃ with 2,6-bis[(3-methoxysalicylidene)hydrazino carbonyl]pyridine (BMSPD) afforded binuclear complexes of the type [Ln₂(BMSPD)(NO₃)₂(H₂O)₅]·3H₂O in case of La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III), and [Ln₂(BMSPD)(NO₃)₂(H₂O)₅] in case of Y(III). The mode of coordination of ligand and the conformational changes on complexation with lanthanides was studied based on elemental analysis, magnetic studies, TG/DTA, IR, ¹H-NMR, Electronic, EPR and Fluorescence spectral studies. The ligand coordinates to one metal centre through enolized deprotonated carbonyls and pyridine nitrogen whereas doubly deprotonated phenolate oxygens and two hydrazonic nitrogens ligate to another lanthanide centre. Both the metal ions are in eight-coordination environments. The ligand and complexes were further tested for antifungal and antibacterial activities.     

Thermal and spectroscopic properties of light lanthanides (III) and sodium complexes of 2,5-pyridinedicarboxylic acid

Pyridine-2,5-dicarboxylic acid, known as isocinchomeric acid is one of six isomers containing two carboxylic groups. Light lanthanide (III) complexes with pyridine-2,5-dicarboxylic acid with general formula Ln₂L₃·nH₂O, where n = 8, 9, were obtained. Their thermal and spectroscopic properties were studied. Sodium salt was obtained as Na₂L·H₂O. Hydrated complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) are stable to 313–333 K, whereas Na₂L·H₂O is stable to about 333 K. Dehydration process for all compounds runs in one stage, next they decompose into appropriate lanthanide oxalates, oxocarbonates carbonates and finally to metal oxides. Bands of νCOOH vibrations at 1736 and 1728 cm⁻¹ disappear on complex spectra and ν_as and ν_s of COO⁻ groups appear thus indicating that complexation process took place.     

Hydrothermal syntheses,structural characterization,and photoluminescent properties of five lanthanide coordination polymers

Five mixed-ligand coordination polymers, [Ln₂(PTCP)₂(m-BDC)₃] _n ?·?nH₂O (Ln?=?Pr (1), Sm (2), Eu (3), Tb (4), Dy (5); m-BDC?=?1,3-benzenedicarboxylate; PTCP?=?2-phenyl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene), were synthesized and characterized by IR spectra, elemental analyses, thermogravimetric analyses, single-crystal X-ray diffraction, and solid-state photoluminescent spectra. X-ray crystallographic analyses reveal that the five complexes are 1-D structures based on dinuclear [Ln₂O₁₂N₄] units and further assembled into 3-D supramolecular networks by hydrogen bonds and π···π stacking interactions. The solids possess high thermal stabilities, with 3 and 4 exhibiting strong pure red and green characteristic emissions of Eu(III) and Tb(III) at room temperature.     

Thermal and Spectral Features of Yttrium and Heavy Lanthanide Complexes with 2,4-dimethoxybenzoic Acid

The complexes of yttrium and heavy lanthanides with 2,4-dimethoxybenzoic acid of the formula: Ln(C₉H₉O₄)₃×nH₂O, where Ln=Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(III), n=2 for Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Y(III), and n=0 for Yb(III) and Lu(III), have been synthesized and characterized by elemental analysis, IR spectroscopy, themogravimetric studies, as well as X–ray and magnetic susceptibility measurements. The complexes have a colour typical of Ln ³⁺ salts (Tb, Dy, Tm, Yb, Lu, Y – white, Ho – cream, Er – pink). The carboxylate group in these complexes is a bidentate, chelating ligand. The compounds form crystals of various symmetry. 2,4-Dimethoxybenzoates of Yb(III) and Lu(III) are isostructural. 2,4-Dimethoxybenzoates of yttrium and heavy lanthanides decompose in various ways on heating in air to 1173 K. The hydrated complexes first lose water to form anhydrous salts and then decompose to the oxides of respective metals. The ytterbium and lutetium 2,4-dimethoxybenzoates decompose in one step to form Yb₂O₃ and Lu₂O₃. The solubilities of the 2,4-dimethoxybenzoates of yttrium and heavy lanthanides in water and ethanol at 293 K are of the order of: ^10–3 and 10^–3 –10^–2 mol dm^–3, respectively. The magnetic moments for the complexes were determined over the range of 77–298 K. They obey the Curie–Weiss law. The results show that there is no influence of the ligand field on the 4f electrons of lanthanide ions. This revised version was published online in August 2006 with corrections to the Cover Date.