Thermal properties and thermochemistry of lanthanide chromates

The behavior of chromates Ln₂(CrO₄)₃·7H₂O and Rb₅Ln(CrO₄)₂ (Ln = La, Pr, Nd, Sm, and Gd) was studied by derivatography as they were heated in air in a temperature interval of 300–1470 K. The high temperature enthalpies of LaCrO₃ and YCrO₃ at 865–1350 K and enthalpies of solution of La₂(CrO₄)₃·7H₂O in a solution of nitric acid at 298 K were measured by calorimetric methods. The standard enthalpies of formation were calculated for some compounds of composition Ln₂(CrO₄)₃·2H₂O and LnCrO₃.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 290–295, February, 2005.     

Novel lanthanide complexeswith di-2-pyridyl ketone-<Emphasis Type="Italic">p</Emphasis>-chloro-benzoylhydrazone

The reaction of a hydrated nitrate salt of lanthanide(III) (Ln=Er, Ho, Tb, Gd) or yttrium(III) (Y) with the ligand di-2-pyridyl ketone-p-Cl-benzoylhydrazone (DpkClBH), afforded air stable solid compounds. The new complexes characterized by means of elemental analysis (C, H, N, Ln), magnetic moment determinations and spectroscopic data (IR, MS). It is proposed that they are cationic of the general type: [Ln(DpkClBH)₂(NO₃)₂]NO₃·nH₂O, (n=2, 1, 1, 1, 1.5 for Ln=Y, Gd, Tb, Ho, Er, respectively). Their thermal decomposition was studied in nitrogen atmosphere, between 25–980°C, by using simultaneous TG/DTG-DTA technique. The IR spectroscopy used to determine the intermediates and the final products. The anhydrous nitrate complexes decomposed to the intermediates Ln(DpkClBH)(NO₃)₂, which upon further heating give a carbonaceous residue of Ln₂O₃ at 980°C. The mass spectra revealed the molecular ions of the complexes and their possible fragmentation pattern.     

Pure trinuclear 4f single-molecule magnets: synthesis, structures, magnetism and ab initio investigation

A family of linear Dy₃ and Tb₃ clusters have been facilely synthesized from the reactions of DyCl₃, the polydentate 3‐methyloxysalicylaldoxime (MeOsaloxH₂) ligand with auxiliary monoanionic ligands, such as trichloroacetate, NO₃^?, OH^?, and Cl^?. Complexes 1 – 5 contain a nearly linear Ln₃ core, with similar Ln???Ln distances (3.6901(4)–3.7304(3) Å for the Dy₃ species, and 3.7273(3)–3.7485(5) Å for the Tb₃ species) and Ln???Ln???Ln angles of 157.036(8)–159.026(15)° for the Dy₃ species and 157.156(8)–160.926(15)° for the Tb₃ species. All three Ln centers are bridged by the two doubly‐deprotonated [MeOsalox]^2? ligands and two of the four [MeOsaloxH]^? ligands through the N,O‐η²‐oximato groups and the phenoxo oxygen atoms (Dy‐O‐Dy angles=102.28(16)–106.85(13)°; Tb‐O‐Tb angles=102.00(11)–106.62(11)°). The remaining two [MeOsaloxH]^? ligands each chelate an outer Ln^III center through their phenoxo oxygen and oxime nitrogen atoms. Magnetic studies reveal that both Dy₃ and Tb₃ clusters exhibit significant ferromagnetic interactions and that the Dy₃ species behave as single‐molecule magnets, expanding upon the recent reports of the pure 4f type SMMs.     

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.     

Oxidation resistance of LnSiON powders (Ln=Y,Gd and La)

For application of LnSiON (Ln=Y, Gd and La) oxynitride materials, e.g. as host-lattices for lamp phosphors, oxidation resistance up to about 600 °C in air is a prerequisite. In this study we prepared LnSiON (Ln=Y, Gd and La) powders by solid state reaction and observed via TGA/DTA-experiments that most compounds are oxidation resistant up to 600 °C in air. The stability in air at high temperatures increases going from Ln₅(SiO₄)₃N, Ln₄Si₂O₇N₂, LnSiO₂N, Ln₂Si₃O₃N₄ to Ln₃Si₈O₄N₁₁. This is explained by an increasing cross-linking between the siliconoxygennitrogen tetrahedra in this sequence. For the lattices with less cross-linking between the siliconoxygennitrogen tetrahedra we observed that the oxidation resistance decreases slightly going from Y and Gd to La. For these lattices, also, an additional weight gain was observed during the oxidation reaction, which was higher than expected for complete oxidation. The additional weight gain was ascribed to an intermediate phase in which nitrogen retention takes place.     

Crystal Structures of the Europium and Yttrium Hydroxychromates Eu(OH)(CrO4) and Y(OH)(CrO4); Structural Evolution as a Function of the Ln3+ Ionic Radius

The compounds Eu(OH)(CrO₄) and Y(OH)(CrO₄) were obtained under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction analysis. They are isostructural and crystallize in the monoclinic system, space group P2₁/n (no. 14) with lattice parameters a = 8.278(1) Å, b = 11.400(2) Å, c = 8.393(1) Å, β = 93.76(2)°, V = 790.3(2) Å³, Z = 4, d = 4.79 g · cm^–3 for Eu(OH)(CrO₄) and a = 8.151(1) Å, b = 11.362(2) Å, c = 8.285(1) Å, β = 94.23(1)°, V = 765.2(2) Å³, Z = 4, d = 3.85 g · cm^–3 for Y(OH)(CrO₄). The [EuO₈] polyhedra form infinite double chains along the a direction, which are connected by common edges and corners. These double chains are related together in the two other directions by the [CrO₄]^2– tetrahedra to form a three‐dimensional network in which channels appear parallel to the [100] direction. We examine the structural evolution, as a function of the Ln³⁺ ionic radius, in the series Ln(OH)(CrO₄) compounds (with Ln = Nd, Eu, Gd, Tb, Er, Yb) and Y(OH)(CrO₄). To determine the best coordination number of each lanthanide and yttrium ions, different calculations of bond valence sum were realized.     

4-Nitro and 4-chloro pyridine-N-oxide complexes of lanthanide perchlorates

Adducts of lanthanide perchlorates with 4-nitro and 4-chloro pyridine-Noxides (4-NPNO and 4-CPNO respectively) have been synthesised for the first time and characterised by analysis, electrolytic conductance, infrared, proton-NMR and electronic spectral data. The complexes are of the compositions Ln₂(NPNO)₁₅ (ClO₄)₆ (Ln = La, Pr, Nd and Gd), Tb(NPNO), (C1O₄)₆), Ln₂(NPNO)₁₃ (C1O₄)₆) (Ln = Dy, Ho, and Yb); Ln (CPNO)₈ (C10₄)₃) (Ln = La, Pr, Nd, Tb, Dy, Ho and Yb) and Ln(CPNO), (C1O₄)₃) (Ln = Sm and Gd). Conductivity and IR data provide evidence for the non-coordinated nature of the perchlorate groups. IR and NMR spectra suggest coordinationvia the oxygen of the N-oxide group. Electronic spectral shapes of the Nd⁺³ and Ho⁺³ complexes are interpreted in terms of eight-and seven-coordinate environments in the case of 4-NPNO complexes and eight-coordination in the case of 4-CPNO complexes. IR data indicate bridged structure in NPNO complexes of lanthanides other than Tb.     

Studies on the Thermal Decomposition of Rare Earth Caproates

The thermal decomposition of rare earth caproates with general formula Ln(C₅H₁₁COO)₃ nH₂O, (where Ln=Y, La-Pr, n=l; Ln=Nd-Er, n=2; Ln=Tm-Lu, n=3) were studied in an air atmosphere. On heating, the hydrated caproates are dehydrated in one step and then the anhydrous complexes decompose to the oxides (Ln₂O₃, Pr₆O₁₁) with formation of the intermediate Ln₂O₂CO₃ (La, Pr-Gd) or directly to the oxides Ln₂O₃, CeO₂, Tb₄O₇(Y, Ce, Tb-Lu). Caproates of rare earth elements are liquefied during dehydration.     

Assisted Self-Assembly to Target Heterometallic Mn-Nd and Mn-Sm SMMs: Synthesis and Magnetic Characterisation of [Mn7Ln3(O)4(OH)4(mdea)3(piv)9(NO3)3] (Ln=Nd,Sm, Eu,Gd)**

In an assisted self-assembly approach starting from the [Mn₆O₂(piv)₁₀(4-Me-py)₂(pivH)₂] cluster a family of Mn−Ln compounds (Ln=Pr−Yb) was synthesised. The reaction of [Mn₆O₂(piv)₁₀(4-Me-py)₂(pivH)₂] ( 1 ) with N-methyldiethanolamine (mdeaH₂) and Ln(NO₃)₃ ⋅ 6H₂O in MeCN generally yields two main structure types: for Ln=Tb−Yb a previously reported Mn₅Ln₄ motif is obtained, whereas for Ln=Pr−Eu a series of Mn₇Ln₃ clusters is obtained. Within this series the Gd^III analogue represents a special case because it shows both structural types as well as a third Mn₂Ln₂ inverse butterfly motif. Variation in reaction conditions allows access to different structure types across the whole series. This prompts further studies into the reaction mechanism of this cluster assisted self-assembly approach. For the Mn₇Ln₃ analogues reported here variable-temperature magnetic susceptibility measurements suggest that antiferromagnetic interactions between the spin carriers are dominant. Compounds incorporating Ln=Nd^III( 2 ), Sm^III( 3 ) and Gd^III ( 5 ) display SMM behaviour. The slow relaxation of the magnetisation for these compounds was confirmed by ac measurements above 1.8 K.     

Synchrotron X‐ray study of noncentrosymmetric Tb3RuO7 with partial structural disorder

Single‐crystal synchrotron X‐ray diffraction reveals partial structural disorder of Tb atoms at 293 K in flux‐grown Tb₃RuO₇ (triterbium ruthenium heptaoxide) crystals. The structure is noncentrosymmetric and composed of infinite single chains of corner‐linked RuO₆ octahedra embedded in a Tb₃O matrix. Two Tb atom sites out of the six crystallographically independent Tb sites are split into two positions. The split sites are separated by approximately 0.3–0.4 Å, with slightly different coordination environments. The RuO₆ octahedra in the present P2₁nb modification have two tilt systems about the a and c axes, in contrast with a single tilt about c in the other Cmcm modifications of Ln₃RuO₇ (Ln = lanthanoid elements).     

Hydrothermal phase equilibria in Ln2O3-H2O systems

Hydrothermal phase equilibria studies have been carried out in the Ln₂O₃-H₂O systems (Ln = La, Pr, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and the stability fields of the phases Ln(OH)₃ LnOOH and Ln₂O₃-C have been established in the pressure-temperature range of 25000 psi and 900° C. The sequioxides Ln₂O₃-C are stable only in the last four systems of Er to Lu along with the Ln(OH)₃ and LnOOH. The systems from Nd to Ho have only Ln(OH)₃ and LnOOH as stable phases and those from La to Pr have only Ln(OH)₃ as the stable phase. The unit cell parameters of trihydroxides deviate from the values reported in the literature and this is attributed to the contamination of CO₂ in the starting material.     

Application of rotate-bomb calorimeter for determining the standard molar enthalpy of formation of Ln(Pdc)3(Phen)

Thirteen solid ternary complexes Ln(Pdc)₃(Phen) (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu;) have been synthesized in absolute ethanol by rare-earth element chloride low hydrate reacting with the mixed ligands of ammonium pyrrolidinedithiocarbamate (APdc) and 1,10-phenanthroline · H₂O (o-Phen · H₂O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes showed that the Ln³⁺ ion was coordinated with six sulfur atoms of three Pdc⁻ and two nitrogen atoms of o-Phen · H₂O. It was assumed that the coordination number of Ln³⁺ is eight. The constant-volume combustion energies of the complexes, Δ_c U, were determined by a precise rotate-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, Δ_c H _m ^o , and standard molar enthalpies of formation, Δ_f H _m ^o were calculated. The text was submitted by the authors in English.     

Hydrothermal synthesis and crystal structure of two new lanthanide coordination polymers with 1,2-phenylenediacetate

Two new compounds {[Ln₂(1,2-pda)₃(H₂O)₂]·?2H₂O} _n (1,2-H₂pda?=?1,2-phenylenediacetic acid, Ln?=?Tb, 1; Ho, 2) were prepared by hydrothermal reaction and characterized by X-ray crystallography. The Ln³⁺ is nine-coordinate by eight oxygen atoms of six 1,2-pda ligands and one oxygen of water. Ln³⁺ ions are bridged by 1,2-pda ligands via bridging/chelating-bridging pentadentate and chelating-bridging/chelating-bridging hexadentate coordination to form 3-D framework structures. Complex 1 emits strong green fluorescence corresponding to ⁵D₄???⁷F_j (j?=?6–3) transitions of the Tb³⁺.     

The First Sodium Uranyl Chromate,Na4[(UO2)(CrO4)3]: Synthesis and Crystal Structure Determination

The first sodium uranyl chromate, Na₄[(UO₂)(CrO₄)₃], has been obtained by high‐temperature solid‐state reaction. The structure (triclinic, P1¯, Z = 2, a = 7.1548(3), b = 8.4420(3), c = 11.5102(5)Å, α = 80.203(1)°, β = 79.310(1)°, γ = 70.415(1)° V = 639.24(4)ų ) has been solved by direct methods and refined on the basis of F² for all unique reflections to R1 = 0.024 [calculated on the basis of 4374 unique observed reflections (‖F_o‖ 4σF)]. The structure is based on chains of composition [(UO₂)(CrO₄)₃] that are parallel to [1¯01]. The chains contain UrO₅ pentagonal bipyramids (Ur = Uranyl) that share all equatorial corners with CrO₄ tetrahedra. Cr(1)O₄ and Cr(3)O₄ tetrahedra bridge between two adjacent UrO₅ bipyramids, whereas Cr(2)O₄ tetrahedra share one corner with one UrO₅ bipyramid each. The [(UO₂)(CrO₄)₃] chains are planar and oriented parallel to (313). The Na⁺ cations provide linkage of the chains in the structure.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

---

Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Structural and Photophysical Properties of Lanthanide Nitrate 1:1 Complexes with planar tridentate nitrogen ligands analogous to 2,2′:6′,2′-terpyridine

The ligand 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (mbzimpy, 1 ) reacts with Eu^III to give [Eu(mbzimpy)(NO₃)₃(CH₃OH)] [ 4 ] whose crystal structure (EuC₂₂H₂₁N₈O₁₀, a = 7.658(3) Å, b = 19.136(2) Å, c = 8.882 Å, β = 104.07(1)°, monoclinic, P2₁, Z = 2) shows a mononuclear structure where Eu^III is ten-coordinate by a meridional tridentate mbzimpy ligand, three bidentate nitrates, and one CH₃OH molecule, leading to a low-symmetry coordination sphere around the metalion. Essentially the same coordination is found in the crystal structure of [Eu(obzimpy)(NO₃)₃] ( 8 ) (EuC₃₅H₄₅N₈O₉, a = 9.095(2) Å, b = 16.624(2) Å, c = 26.198(6) Å, β = 95.85(1)°, monoclinic, P2₁/c, Z = 4) obtained by reaction of 2,6-bis(1-octylbenzimidazol-2-yl)pyridine (obzimpy, 2 ) with Eu^III. Detailed photophysical studies of crystalline [Ln(mbzimpy)(NO₃)₃(CH₃OH)] and [Ln(obzimpy)(NO₃)₃] complexes (Ln = Eu, Gd, Tb, Lu) show that 1 and 2 display ¹ππ* and ³ππ* excited states very similar to those observed in 2,2′:6′,2″-terpyridine, leading to efficient ligand to Ln^III intramolecular energy transfer. Spectroscopic results show that an extremely efficient mbzimpy-to-Eu^III transfer occurs in [Ln(mbzimpy)(NO₃)₃(CH₃OH)] and in the case of Tb^III, a Tb^III-to-mbzimpy back transfer is also implied in the deactivation process. The origin of these peculiar effects and the influence of ligand design by going from mbzimpy to obzimpy are discussed. ¹H-NMR and luminescence data indicate that the structure found in the crystal is essentially maintained in solution.     

Stabilization Of The CN35− Anion In Recoverable High-pressure Ln3O2(CN3) (Ln=La,Eu, Gd,Tb, Ho,Yb) Oxoguanidinates

A series of isostructural Ln₃O₂(CN₃) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25–54 GPa) high-temperature (2000–3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln₃O₂(CN₃) solids are composed of the hitherto unknown CN₃⁵⁻ guanidinate anion—deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln₃O₂(CN₃) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln₃O₂(CN₃) compounds are recoverable to ambient conditions. The stabilization of the CN₃⁵⁻ guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry.     

Synthesis and characterisation of TlLn(SO4)2·xH2O (Ln=La-Tb)

The compounds TlLn(SO₄)₂·2H₂OLn=La, Ce, Pr, Nd and Tl[Ln(SO₄)₂(H₂O)₃]·H₂OLn=Nd, Sm, Eu, Gd, Tb have been isolated from aqueous solutions of the corresponding sulfates. The dihydrates are all isomorphous and crystallize monoclinic, space groupP2₁/n,Z=4. The compounds which belong to the second type are also isomorphous and crystallize in monoclinic space groupP 2₁/c withZ=4.The dehydration has been studied by thermogravimetry, differential scanning calorimetry and isothermal weight change determination. The dihydrates dehydrate in a single step. For the tetrahydrates the reaction is more complex, however no intermediate phases could be isolated.The unit cell parameters, the dehydration temperatures and the dehydration enthalpies are correlated to the ionic radii ofLn ³⁺.

---

Synthese und Charakterisierung von TlLn(SO₄)₂·xH₂O (Ln=La-Tb)

Zusammenfassung Die Verbindungen TlLn(SO₄)₂·2H₂OLn=La, Ce, Pr, Nd und Tl[Ln(SO₄)₂(H₂O)₃]·H₂OLn=Nd, Sm, Eu, Gd, Tb wurden aus wäßrigen Lösungen der entsprechenden Sulfate isoliert. Die Dihydrate sind alle isomorph und kristallisieren monoklin, RaumgruppeP 2₁/n,Z=4. Die Verbindungen des zweiten Typs sind auch isomorph und kristallisieren in der monoklinen RaumgruppeP 2₁/c mitZ=4.Die Dehydration wurde mit TG, DSC und dem isothermalen Gewichtsverlust untersucht. Die Entwässerung der Dihydrate verläuft in einer Stufe, die von Tetrahydraten aber in mehreren Stufen mit keiner isolierbaren Zwischenphase.Die Gitterkonstanten, die Dehydratations-Temperaturen und -Enthalpien wurden mit den Ionenradien vonLn ³⁺ korreliert.

     

Nanostructuring phenomena in oxygen-conducting complex oxides of heavy REE

In complex oxides of REE (Ln₄M₃O₁₂ (Ln = Tm, Lu; M = Zr, Hf), Ln₂TiO₅ (Ln = Er-Yb)) and Ho₂TiO₅, the following phase transitions of the order-disorder type are studied for different cooling rates: rhombohedral δ-phase-defective fluorite in Ln₄M₃O₁₂ (Ln = Tm, Lu; M = Zr, Hf), pyrochlor-like phasedefective fluoride in Ln₂TiO₅ (Ln = Er-Yb), and hexagonal β-phase-pyrochlor in Ho₂TiO₅. The presence of nanostructuring phenomena typical of fluorite-like polymorphous modifications of complex oxides in the Ln₂O₃-MO₂ (Ln = Ho-Lu; M = Ti, Zr, Hf) systems is confirmed. The conductivity of polymorphous modifications of Ln₄Zr₃O₁₂ (Ln = Tm, Lu;) and Ln₂TiO₅ (Ln = Ho-Yb) with different thermal prehistory is studied. The comparative studies of the oxygen-ionic conductivity of fluorite- and pyrochlor-like Ln₂TiO₅ (Ln = Ho-Yb), pyrochlor Ho₂TiO₅, and β-Ho₂TiO₅ and also of the conductivity of fluorite-like compounds and δ-Ln₄Zr₃O₁₂ (Ln = Tm, Lu) are carried out. The oxygen-ionic conductivity of complex oxides in the Ln₂O₃-MO₂ (Ln = Er-Lu; M = Ti, Zr, Hf) system is shown to decrease in the following series: defective pyrochlor-defective fluorite-rhombohedral δ-phase ∼ hexagonal β-phase.     

Syntheses,characterization and thermal properties of lanthanide complexes with 2-mercaptonicotinic acid

Fourteen new complexes with the general formula of Ln(Hmna)₃·nH₂O (n=2 for Ln=La-Ho and n=1 for Er-Lu, H₂mna=2-mercaptonicotinic acid) were synthesized and characterized by elemental analyses, IR spectra and thermogravimetric analyses. In addition, molar specific heat capacities were determined by a microcalorimeter at 298.15 K. The IR spectra of the prepared complexes revealed that carboxyl groups of the ligands coordinated with Ln(III) ions in bidentate chelating mode. Hydrated complexes lost water molecules during heating in one step and then the anhydrous complexes decomposed directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The values of molar specific heat capacities for fourteen solid complexes were plotted against the atomic numbers of lanthanide, which presented as ‘tripartite effect’. It suggested a certain amount of covalent character existed in the bond of Ln³⁺ and ligands, according with nephelauxetic effect of 4f electrons of rare earth ions.