Spectral and Thermal Studies of Rare Earth Complexes With 2,4,6-trimethylbenzoic Acid

The rare earth element 2,4,6-trimethylbenzoates were prepared as solids with the general formula Ln(C₁₀ H₁₁ O₂ )₃ ×n H₂ O, where n =2 for Ln =Y, La–Nd, and n =1 for Ln =Sm–Lu. The IR spectra of the complexes prepared were recorded and their solubilities in water and thermal decomposition in the air were investigated. During heating the hydrated complexes lose all the crystallization water molecules in one (Y, Ce–Lu) or two steps (La) and then the anhydrous complexes decompose either directly to oxides (Y, Ce, Pr, Sm–Lu) or with intermediate formation oxocarbonates Ln₂ O₂ CO₃ (La, Nd). The carboxylate groups in the complexes prepared act probably as mono- and bidentate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis,spectroscopic and thermal studies of 2,3-naphthalenedicarboxylates of rare earth elements

The complexes of rare earth elements with 2,3-naphthalenedicarboxylic acid of the formula: Ln₂(C₁₂H₆O₄)₃·nH₂O, where Ln = La(III)-Lu(III) and Y(III); n = 3 for La(III), Ce(III); n = 6 for Pr(III)-Yb(III) and Y(III) and n = 5 for Lu(III) have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis (TG, DTG, DTA and TG-FTIR) and X-ray analysis. They are sparingly soluble in water and stable at room temperature. During heating in air atmosphere, they lose all water molecules in several steps, generally in two or three steps, except for the La(III) and Ce(III) complexes which lose all water molecules in one step. The anhydrous compounds are stable up to about 773 K and then decompose to corresponding oxides. The thermal decomposition is connected with the release of water molecules (443 K), carbon dioxide (713 K) and hydrocarbons.     

Thermal decompositions of light lanthanide aconitates

The conditions of thermal decomposition of Y, La, Ce(III), Pr, Nd, Sm, and Gd aconitates have been studied. On heating, the aconitate of Ce(III) loses crystallization water to yield anhydrous salt, which then is transformed in to oxide CeO₂. The aconitates of Y, Pr, Nd, Sm, Eu and Gd decompose in three stages. First, aconitates undergo dehydration to form the anhydrous salts, which next decompose to Ln₂O₂CO₃. In the last one the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ is accompanied by endothermic effect. Dehydration of aconitate of La undergoes in two stages. The anhydrous complex decomposes to La₂O₂CO₃; this subsequently decomposes to La₂O₃.     

Thermal decomposition of rare earth element enanthates

The conditions of formation of Y, La and lanthanide (from Ce(III) to Lu) enanthates were worked out, their composition and their solubilities in water at 291 K were determined, and the conditions of their thermal decomposition were studied. They were prepared as crystalline solids with general formula Ln(C₇H₁₃O₂)₃·nH₂O, wheren=2–10. On heating, they decompose in two or three steps. They first lose some water molecules and then decompose to the oxides directly (salts of Y and heavy lanthanides) or via the intermediate formation of Ln₂O₂CO₃ (salts of La, Pr, Nd, Sm and Eu). Only yttrium enanthate dihydrate loses 2 water molecules on heating to form an anhydrous complex, which decomposes directly to Y₂O₃. The temperatures of dehydration are similar for all complexes (323–343 K), while the temperatures of oxide formation vary irregularly from 823 K for CeO₂ to 1078 K for La₂O₃.     

Thermal decompositions of heavy lanthanide aconitates

The conditions of thermal decomposition of Tb(III), Dy, Ho, Er, Tm, Yb and Lu aconitates have been studied. On heating, the aconitates of heavy lanthanides lose crystallization water to yield anhydrous salts, which are then transformed into oxides. The aconitate of Tb(III) decomposes in two stages. First, the complex undergoes dehydration to form the anhydrous salt, which next decomposes directly to Tb₄O₇. The aconitates of Dy, Ho, Er, Tm, Yb and Lu decompose in three stages. On heating, the hydrated complexes lose crystallization water, yielding the anhydrous complexes; these subsequently decompose to Ln₂O₃ with intermediate formation of Ln₂O₂CO₃.     

Synthesis And Characterization Of Complexes Of Rare Earth Elements With 1,1-Cyclobutanedicarboxylic Acid

The complexes of yttrium and lanthanide with 1,1-cyclobutanedicarboxylic acid of the formula: Ln₂(C₆H₆O₄)₃⋅nH₂O, where n=4 for Y, Pr–Tm, n=5 for Yb,Lu, n=7 for La, Ce have been studied. The solid complexes have colours typical of Ln³⁺ ions. During heating in air they lose water molecules and then decompose to the oxides, directly (Y, Ce, Tm, Yb) or with intermediate formation. The thermal decomposition is connected with released water (313–353 K), carbon dioxide, hydrocarbons(538–598 K) and carbon oxide for Ho and Lu. When heated in nitrogen they dehydrate to form anhydrous salt and next decompose to the mixture of carbon and oxides of respective metals. IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of Y,La and lanthanide benzene-1,2-dioxyacetates in an air atmosphere

The thermal decompositions of Y, La and lanthanide (from Ce(III) to Lu(III) benzene-1,2-dioxyacetates with general formula Ln₂(C₁₀H₈O₆)₃·nH₂O were studied. The hydrated complexes first lose water of crystallization in one or two steps to yield anhydrous compounds or hydrates containing coordination water molecules, and then decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ with formation of intermediates, carbonates and oxycarbonates (La, Pr-Eu), oxycarbonates (Y, Tb-Lu) or carbonate (Gd) only. Anhydrous cerium(III) benzene-1,2-dioxyacetate decomposes on heating directly to CeO₂.     

Thermal and spectral studies of rare earth element 3-methoxy-4-methylbenzonates

3-Methoxy-4-methylbenzoates of Y(III) and lanthanide(III) (La-Lu) were prepared as crystalline compounds with molar ratio of metal to organic ligand of 1.0:3.0 and general formula Ln(C₉H₉O₃)3·nH₂O, where n=2 for Y, La-Er and n=0 for Tm-Lu. IR spectra of the prepared complexes suggest that carboxylate groups are bidentate chelating. During heating dihydrated complexes lose crystallization water molecules in one (Y, La, Pr-Er) or two steps (Ce) and then all the anhydrous complexes decompose directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇.Vadim Mamleev is grateful to Region Nord-pas-de-Calais (France) for financial support and to laboratory PERF of ENSCL for its kind invitation to continue the joint work on thermal analysis.     

Structural and thermal properties of rare earth complexes with 2,2′-biphenyldicarboxylic acid

Rare earth complexes with 2,2′-biphenyldicarboxylic acid (diphenic acid = H₂dpa) were obtained as hydrated precipitates of the general formula Ln₂(C₁₄H₈O₄)₃∙nH₂O, where n = 3 for the of Y(III) and Ce(III)–Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30–210 °C in one step and form anhydrous compounds, which are stable up to 315–370 °C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)–Er(III) complexes) crystal systems.     

Spectral and thermal investigation of rare earth element 4-methoxy-2-methylbenzoates

4-Methoxy-2-methylbenzoates of Y(III) and lanthanides(III) (La-Lu) were prepared as crystalline anhydrous complexes with general formula Ln(C₉H₉O₃)₃ (complexes of La and Pr as monohydrates). Monohydrates heated in air lose crystallization water molecule and then anhydrous complexes decompose directly to oxides. Only La(III) complex decomposes to oxide with intermediate formation La₂O₂CO₃. The carboxylate group in the studied complexes is a tridentate chelating - bridging or bidentate chelating (Y). This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of scandium(III) o-nitrobenzoate,o-chlorobenzoate,o-methylbenzoate,o-hydroxybenzoate and o-aminobenzoate in air atmosphere

The conditions of thermal decomposition of scandium o-nitrobenzoate, o-chlorobenzoate, o-methylbenzoate, o-hydroxybenzoate and o-aminobenzoate were studied. On heating, the carboxylates decompose in two steps, only scandium anthranilate decomposes in one step. The hydrated complexes first lose water of crystallization and then are transformed to Sc₂O₃. The dehydration of the complexes is an endothermic process and the decomposition of anhydrous complexes is strongly exothermic. Scandium o-nitrobenzoate decomposes explosively.     

Synthesis, Characterization and thermal behaviour of hemimellitic acid complexes with lanthanides(III)

The complexes of lanthanides(III) with hemimellitic acid (1,2,3-benzenetricarboxylic acid, H₃btc) of the formula Ln(btc)·nH₂O, where Ln=lanthanide(III) ion and n=2?6 were prepared and characterized by elemental analysis, infrared spectra, X-ray diffraction patterns and thermal analysis. The IR spectra of the complexes indicate coordination of lanthanides(III) through all carboxylate groups. The complexes of La(III), Ce(III), Pr(III) and Er(III) are amorphous. On heating in air atmosphere all complexes lose water molecules and next anhydrous compounds decompose to corresponding metal oxides.     

Thermal decompositions of scandium(III) 2,4-dinitrobenzoate, 3,5-dinitrobenzoate, 2,4-dichlorobenzoate and 3,4-diaminobenzoate in air atmosphere

The thermal decompositions of scandium 2,4-dinitrobenzoate, 3,5-dinitrobenzoate, 2,4-dichlorobenzoate and 3,4-diaminobenzoate were studied. On heating, the carboxylates decompose in two steps. The hydrated complexes first lose crystallization water and are transformed to Sc₂O₃. The dehydration of the complexes is accompanied by an endothermic effect and decomposition of the anhydrous or monohydrate complezes by strong exothermic effects. Scandium 2,4-dinitrobenzoate and 3,5-dinitrobenzoate decompose explosively.     

Thermal and spectroscopic investigations of new lanthanide complexes with 1,2,4-benzenetricarboxylic acid

The new 1,2,4-benzenetricarboxylates of lanthanide(III) of the formula Ln(btc)·nH₂O, where btc is 1,2,4-benzenetricarboxylate; Ln is La-Lu, and n=2 for Ce; n=3 for La, Yb, Lu; and n=4 for Pr-Tm were prepared and characterized by elemental analysis, infrared spectra and X-ray diffraction patterns. Polycrystalline complexes are isotructural in the two groups: La-Tm and Yb, Lu. IR spectra of the complexes show that all carboxylate groups from 1,2,4-benzentricarboxylate ligands are engaged in coordination of lanthanide atoms. The thermal analysis of the investigated complexes in air atmosphere was carried out by means of simultaneous TG-DTA technique. The complexes are stable up to about 30°C but further heating leads to stepwise dehydration. Next, anhydrous complexes decompose to corresponding oxides. The combined TG-FTIR technique was employed to study of decomposition pathway of the investigated complexes.     

The Complexes of Rare Earth Elements with 2,5-Dihydroxybenzoic Acid Preparation, properties and thermal decomposition

The conditions of the formation of rare earth(III) 2,5-dihydroxybenzoates have been studied; their compositions and solubilities in water at 293 K have been determined. The IR spectra of the anhydrous complexes with the general formula Ln(C7H5O4)3 have been recorded and their thermal decompositions in static air determined. During heating the anhydrous complexes of Y, Pr-Lu decompose to the oxides Ln2O3, Pr6O11 and Tb4O7 with formation of the intermediate Ln2(C7H4O4)3. The lanthanum complex decomposes to the oxide in three steps forming La2(C7H4O4)3 and La2O2CO3 as intermediates and the Ce(III) complex decomposes directly to CeO2. The properties of rare earth 2,5- and 2,4-dihydroxybenzoates have been compared. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of rare earthp-aminosalicylates in air atmosphere

The conditions of thermal decomposition of thep-aminosalicylates of Y, La and the lanthanides from Ce(III) to Lu have been studied. On heating, the hydrated complexes of La and the light lanthanides decompose to the oxides with the intermediate formation of Ln₂[H₂N·C₆H₃(O)COO]₃. Only the complex of La decomposes to La₂O₃ through La₂[H₂N·C₆H₃(O)COO]₃ and La₂O₂CO₃. The anhydrous complexes of the heavy lanthanides decompose directly to the oxides, whereas the anhydrous complex of Y decomposes to Y₂O₃ via Y₂[H₂N·C₆H₃(O)COO]₃ formation. During heating, the hydrated complexes lose crystallization water and decompose simultaneously, and the endothermic effect of dehydration is masked by the strong exothermic effect of burning of the organic ligand.

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Zusammenfassung Es wurden die Bedingungen für die thermische Zersetzung derp-Aminosalicylate von Y, La und der Lanthanoide von Ce(III) bis Lu untersucht. Beim Erhitzen zersetzen sich die hydratierten Komplexe von La und der leichteren Lanthanoide unter Bildung des Zwischenproduktes Ln₂[H₂NC₆H₃(O)COO]₃ in ihre Oxide. Nur der Komplex mit La zersetzt sich zu La₂O₃ über die Zwischenstufen La₂[H₂NC₆H₃(O)COO]₃ und La₂O₂CO₃. Die wasserfreien Komplexe der schweren Lanthanoide zersetzen sich direkt in die Oxide, wÄhrend sich der wasserfreie Komplex von Y über die Bildung von y₂[H₂NC₆H₃(O)COO]₃ in y₂O₃ zersetzt. Beim Erhitzen verlieren die hydratierten Komplexe ihr Kristallwasser und zersetzen sich gleichzeitig, der endotherme Effekt der Dehydratation wird durch den starken exothermen Effekt der Verbrennung der organischen Liganden überdeckt.

     

Thermal properties of lanthanide(III) complexes with 2-aminoterephthalic ACID

The complexes of yttrium(III) and lanthanides(III) with 2-aminoterephthalic acid form the isostructural series of triclinic compounds with a space group P from La to Lu and they have the general formula of Ln₂(C₈H₅O₄N)₃·8H₂O. On heating in air or inert gas atmosphere they lose all water molecules in the temperature range 50–200°C in one or two steps. The anhydrous compounds are stable from 360 to 435°C and then decompose to oxides.     

Reactions and phases within the TeO2-rich part of the Bi2O3-TeO2 system

The complexes of heavy lanthanides and yttrium with 2,3-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), Y(III), and n=2 for Tb(III), Dy(III), Ho(III), Y(III), n=1 for Er(III), Tm(III), n=0 for Yb(III) and Lu(III) have been synthesized and characterized by elemental analysis, ir spectroscopy, thermogravimetric studies and x-ray diffraction measurements. The complexes have colours typical for Lnł³⁺ ions (Tb(III), Dy(III), Tm(III), Yb(III), Lu(III), Y(III) - white; Ho(III) - cream and Er(III) - salmon). the carboxylate groups in these complexes are a symmetrical, bidentate, chelating ligand or tridentate chelating-bridging. they are isostructural crystalline compounds characterized by low symmetry. On heating in air to 1273 k the 2,3-dimethoxybenzoates of heavy lanthanides and yttrium decompose in various ways. The complexes of Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Y(III) at first dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. 2,3-dimethoxybenzoates of Yb(III) and Lu(III) are directly decomposed to oxides. When heated in nitrogen the hydrates also dehydrate in one step to form the anhydrous complexes that next form the mixture of carbon and oxides of respective metals or their carbonates. The solubility of the yttrium and heavy lanthanide 2,3-dimethoxybenzoates in water at 293 k is of the order of 10^-2 mol dm^-3. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Thermal decomposition of light lanthanide diglycolates

The conditions of thermal decomposition of La, Ce(III), Pr, Nd, Sm, Eu and Gd diglycolates have been studied. On heating, the diglycolates of Ce(III), Pr, Eu and Gd lose crystallization water and yield anhydrous salts, which are then transformed into oxides. The diglycolates of La, Nd and Sm are decomposed in three stages. First, the diglycolates undergo dehydration to form the anhydrous salts, which are next decomposed to Ln₂O₂CO₃. In the last step the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ takes place, accompanied by an endothermic effect.