Single-Crystal-to-Single-Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework

Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single-crystal-to-single-crystal (SCSC) transformation is presented. Soaking single crystals of K₆[Rh₄Zn₄O(l -cys)₁₂] (K₆[ 1 ]; l -H₂cys=l -cysteine) in a water/ethanol solution containing Ln(OAc)₃ (Ln³⁺=lanthanide ion) results in the exchange of K⁺ by Ln³⁺ with retention of the single crystallinity, producing Ln₂[ 1 ] ( 2_Ln ) and Ln_0.33[Ln₄(OH)₄(OAc)₃(H₂O)₇][ 1 ] ( 3_Ln ) for early and late lanthanides, respectively. While the Ln³⁺ ions in 2_Ln exist as disordered aqua species, those in 3_Ln form ordered hydroxide-bridged cubane clusters that connect [ 1 ]⁶⁻ anions in a 3D metal-organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts.     

Synthesis,Crystal Structure,Fluorescent and Antioxidation Properties of Cerium(III) and Europium(III) Complexes with Bis(3‐methoxysalicylidene)‐3‐oxapentane‐1,5‐diamine

Two aliphatic ether Schiff base lanthanide complexes (Ln = Eu, Ce) with bis(3‐methoxysalicylidene)‐3‐oxapentane‐1,5‐diamine (Bod), were synthesized and characterized by physicochemical and spectroscopic methods. [Eu(Bod)(NO₃)₃] ( 1 ) is a discrete mononuclear species and [Ce(Bod)(NO₃)₃DMF]_∞ ( 2 ) exhibits an inorganic coordination polymer. In the two complexes, the metal ions both are ten‐coordinated and the geometric structure around the Ln^III atom can be described as distorted hexadecahedron. Under excitation at room temperature, the red shift in the fluorescence band of the ligand in the complexes compared with that of the free ligand can be attributed to coordination of the rare earth ions to the ligand. Moreover, the antioxidant activities of the two complexes were investigated. The results demonstrated that the complexes have better scavenging activity than both the ligand and the usual antioxidants on the hydroxyl and superoxide radicals.     

Intermolecular dynamics and paramagnetic properties of ethylenediaminetetraacetate complexes with the yttrium subgroup rare earth elements using nuclear magnetic resonance

¹H nuclear magnetic resonance (NMR) measurements are reported for the D₂O solutions of [Ln³⁺(EDTA^4?)]^? complexes, where EDTA^4? is ethylenediaminetetraacetate anion, Ln³⁺ = Tb³⁺ (I), Ho³⁺ (II), Tm³⁺ (III), Yb³⁺ (IV) and Lu³⁺ (V). Temperature dependencies of the ¹H NMR spectra of paramagnetic I–IV have been analyzed using the dynamic NMR methods. It is found that the activation free energies (ΔG^?₂₉₈ ) of the intermolecular EDTA ions exchange at [Ln³⁺(EDTA^4?)]^? complexes are 60±3 (I), 66±3 (II), 69±3 (III) and 74±3 (IV) kJ/mol (at pD = 7). A monotonic increase of the free energy of chemical exchange processes along the series of lanthanide [Ln³⁺ (EDTA^4?)]^? complexes is probably related to the lanthanide contraction. The obtained results indicate that coordination compounds I–IV may be considered as thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution. Copyright © 2012 John Wiley & Sons, Ltd.     

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III)

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III) were obtained as mono-, di-, tri-or tetrahydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Er, n=2 for Ln=Tb, Dy, Tm, Y, n=3 for Ln=Ho and n=4 for Yb and Lu. The complexes were characterized by elemental analysis, FTIR spectra, TG, DTA and DSC curves, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate chelating ligand. All complexes are polycrystalline compounds. The values of enthalpy, ΔH, of the dehydration process for analysed complexes were also determined. The solubilities of heavy lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁴ mol dm⁻³. The magnetic moments were determined over the range of 76–303 K. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Single‐Crystal‐to‐Single‐Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework

Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single‐crystal‐to‐single‐crystal (SCSC) transformation is presented. Soaking single crystals of K₆[Rh₄Zn₄O(l ‐cys)₁₂] (K₆[ 1 ]; l ‐H₂cys=l ‐cysteine) in a water/ethanol solution containing Ln(OAc)₃ (Ln³⁺=lanthanide ion) results in the exchange of K⁺ by Ln³⁺ with retention of the single crystallinity, producing Ln₂[ 1 ] ( 2_Ln ) and Ln_0.33[Ln₄(OH)₄(OAc)₃(H₂O)₇][ 1 ] ( 3_Ln ) for early and late lanthanides, respectively. While the Ln³⁺ ions in 2_Ln exist as disordered aqua species, those in 3_Ln form ordered hydroxide‐bridged cubane clusters that connect [ 1 ]^6? anions in a 3D metal‐organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts.     

Mono and trinuclear lanthanide complexes of 13-membered tetraaza macrocycle: Synthesis and characterization

The reaction of 1,8-diamino-3,6-diazaoctane and diethyl malonate in dry methanol yielded a 13-membered macrocycle. Complexes of the type [Ln(tatd)Cl₂ (H₂O)₃]Cl [Ln^III=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy; tatd=1, 5, 8, 11-tetra-azacyclotridecane-2,4-dione] have been synthesized by template condensation. The complex [La(tatd)Cl₂ (H₂O)₃]Cl in methanol was reacted with lanthanide chlorides to yield the trinuclear complexes of type [2{La(tatd)Cl₂(H₂O)₃}LnCl₃]Cl₂ [Ln^III=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy]. The chemical compositions of mono and trinuclear complexes have been established on the basis of analytical, molar conductance, electrospray (ES) and fast atom bombardment (FAB) mass data. In mononuclear complexes the Ln³⁺ ion is encapsulated by four ring nitrogens and in trimetallic complexes the exo-carbonyl oxygens of two mononuclear units coordinate to the Ln³⁺ ions resulting in a polyhedron around the lanthanide ions. Thus the macrocycle is bonded in a tetradentate fashion in the former complexes and hexadentate in the latter. The coordination number nine around the encapsulated Ln³⁺ and seven around the exo-oxygen bonded Ln³⁺ ions are established. The symmetry of the ligand field around the metal ions is indicated from the emission spectra.     

Octanuclear Ni4Ln4 Coordination Aggregates from Schiff Base Anion Supports and Connecting of Two Ni2Ln2 Cubes: Syntheses,Structures, and Magnetic Properties

A family of 3d–4f aggregates have been reported through guiding the dual coordination modes of ligand anion (HL^?) and in situ generated ancillary bridge driven self‐assembly coordination responses toward two different types of metal ions. Reactions of lanthanide(III) nitrate (Ln=Gd, Tb, Dy, Ho and Yb), nickel(II) acetate and phenol‐based ditopic ligand anion of 2‐[{(2‐hydroxypropyl)imino}methyl]‐6‐methoxyphenol (H₂L) in MeCN‐MeOH (3 : 1) mixture and LiOH provided five new octanuclear Ni‐4f coordination aggregates from two Ni₂Ln₂ cubanes. Single‐crystal X‐ray diffraction analysis reveals that all the members of the family are isostructural, with the central core formed from the coupling of two distorted [Ni₂Ln₂O₄] heterometallic cubanes [Ni₂Ln₂(HL)₂(μ₃‐OH)₂(OH)(OAc)₄]⁺ (Ln=Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ) and Yb ( 5 )). Higher coordination demand of 4f ions induced the coupling of the two cubes by (OH)(OAc)₂ bridges. Variable temperature magnetic study reveals weak coupling between the Ni²⁺ and Ln³⁺ ions. For the Tb ( 2 ) and Dy ( 3 ) analogs, the compounds are SMMs without an applied dc field, whereas the Gd ( 1 ) analogue is not an SMM. The observation revealed thus that the anisotropy of the Ln³⁺ ions is central to display the SMM behavior within this structurally intriguing family of compounds.     

Solventothermal syntheses, structures and photoluminescence of two-dimensional lanthanide coordination polymers with adipic acid

Four lanthanide coordination polymers formulated as [Ln₂(Ad)₃(H₂O)₄] · 0.25H₂O ( Ln = Tb (I), Pr (II), Ho (III), Dy (IV); H₂Ad = adipic acid), have been solventothermally synthesized from the self-assembly of the lanthanide ions (Ln³⁺) with the exible adipic dicarboxylate ligand. All of them were characterized by IR spectroscopy and single-crystal X-ray diffraction. Structural analyses revealed that these complexes had intricate two-dimensional interpenetrated metal-organic networks. In addition, the photoluminescent properties of complex I was discussed in detail, which shows strong green emission, corresponds to ⁵ D ₄ → ⁷ F ₅ transition of Tb³⁺ ions.     

Synthesis,structures and magnetic properties of a series of polynuclear copper(II)‐lanthanide( III) complexes assembled with carboxylate and hydroxide ligands

Heterometallic copper(II)‐lanthanide(III) complexes have been made with a variety of exclusively O‐donor ligands including betaines (zwitterionic carboxylates) and chloroacetate, which are dinuclear CuLn, tetranuclear Cu₂Ln₂, pentanuclear C_u3Ln₂, and octadecanuclear C_u12 complexes. The results show that subtle changes in both the carboxylates and acidity of the reaction solution can cause drastic changes in the structures of the products. Magnetic studies exhibit that shielding of the Ln³⁺ 4f electrons by the outer shell electrons is very effective to preclude significant coupling interaction between the Ln³⁺ 4f electrons and Cu²⁺ 3d electrons in either a mono‐atomic hydroxide‐bridged, or a carboxylate‐bridged system.     

Photoluminescence Properties of Lanthanide‐Organic Frameworks (LnOFs) with Thiophene‐2,5‐Dicarboxylate and Acetate

S‐heterocyclic dicarboxylic acid, thiophene‐2,5‐dicarboxylic acid (H₂TDC), was employed to construct a series of lanthanide‐organic frameworks (LnOFs) with coligand acetate, formulated as [Ln(TDC)(OAc)(H₂O)]_n [Ln = Eu ( 1 ), Tb ( 2 ), Gd ( 3 ), Dy ( 4 ), Sm ( 5 )] under hydrothermal conditions. Structure analysis reveals that 1 – 5 have dinuclear 3D metal organic frameworks (MOFs), in which TDC^2– and OAc^– display (κ¹‐κ¹)‐(κ¹–κ¹)‐μ₄ and (κ²‐κ¹)‐μ₂ coordination fashions, respectively. The dehydrated products of all compounds show high thermal stability above 410 °C. As for 1 , 2 , 4 , and 5 , the photoluminescence analyses exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible region. In particular, compound 2 displays bright green luminescence in the solid state with ⁵D₄ lifetime of 0.510 ms and relative high overall quantum yield of 16 %, based on an ideal energy gap between the lowest triplet state energy level of H₂TDC ligand and the ⁵D₄ state energy level of Tb³⁺. The energy transfer mechanisms in compounds 1 and 2 were also discussed.     

Yttrium(III) and lanthanide(III) perchlorate complexes with the 2,2,6,6- tetramethylpiperidine nitroxide free radical

Summary 2,2,6,6-Tetramethylpiperidine nitroxide free radical (TMPNO) complexes with Y³⁺ and Ln³⁺ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er or Yb) perchlorates were synthesized and characterized by means of i.r. and e.s.r. spectral, magnetic susceptibility and molar conductance studies. The new complexes are of the general type [M(TMPNO-)₂(OH₂)₃(OCIO₃)](ClO₄)₂ (M = Y or Ln), involving two TMPNO;, three aqua and one unidentate perchlorato ligand in the complex cation, and two anionic C10₄ groups. The NO bond-order in coordinated TMPNO is apparently two, as suggested by the i.r. evidence. The magnetic susceptibility and e.s.r. data were interpreted in terms of partial spin-spin coupling interaction between the unpaired electrons of the two TMPNO- ligands, as well as unpaired f electrons, in the case of paramagnetic lanthanide(Ill) ions. Severe steric hindrance, introduced during coordination of the free radical ligand through the NO oxygen atom, does not seem to allow accommodation of more than two TMPNO molecules in the inner coordination sphere of the central Y³⁺, or Ln³⁺ ion.To whom all correspondence should be directed.     

Synthesis, crystal structures and photoluminescent properties of lanthanide supramolecular complexes with 4-oxo-1(4H)-quinolineacetate

Five new lanthanide supramolecular complexes, namely, [Sm(oqa)₂(H₂O)₄]₂ (ClO₄)₂·(bpy)₂ (1), [Ln(oqa)₃]·2H₂O [Ln=Sm(2), Gd(3)] and [Ln(oqa)₂(NO₃)(H₂O)] [Ln=Pr(4), Eu(5)] (oqa=4-oxo-1(4H)-quinolineacetate, bpy=4,4′-bipyridine), have been synthesized under hydrothermal conditions. These complexes exhibit three typical structure features. Complex 1 possesses a dimeric structure, which is further connected together through hydrogen bonds and π-π attractions, forming a 3D supramolecular framework. Compounds 2-3 are isomorphous and contain 1D ring-like chains, which are further interconnected by the oqa ligands into 2D sheet-like structures. 4 and 5 exhibit eight-connected 3D network of 4²⁴·6⁴-bcu topology. The various coordination modes of carboxylate ligands and the selection of the counterions have clearly affected the topological structures. Furthermore, the solid-state luminescent properties of complexes 1, 2 and 5 were investigated at room temperature and they show intense, characteristic emissions in the visible region.     

Synthesis,Structures, and Magnetic Properties of Zigzag Tetranuclear Lanthanide Complexes

Five isostructural tetranuclear lanthanide complexes with the general formula [Ln₄(teaH₂)₂(teaH)₂(NO₃)₆] · 2CH₃OH [Ln³⁺ = Dy³⁺ ( 1 ), Tb³⁺ ( 2 ), Ho³⁺ ( 3 ), Er³⁺ ( 4 ), and Gd³⁺ ( 5 )] were successfully synthesized by the reaction of various lanthanide nitrate and triethanolamine (teaH₃) ligand. Single crystal X-ray analyses reveal the eight-coordinate Ln³⁺ centers adopt a slightly distorted triangular dodecahedron geometry and nine-coordinate Ln³⁺ ions own an approximately capped square antiprism environment in similar zigzag Ln4 core. Magnetic studies demonstrate the presence of anitferromagnetic interactions between Ln³⁺ centers without obvious SMM behavior.     

Thermal,spectral and magnetic behaviour of 4-chloro-2-methoxybenzoates of light lanthanides(III)

4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁵ mol dm⁻³. The magnetic moments were determined over the range of 77–300 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 indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Periodicity of Single-Molecule Magnet Behaviour of Heterotetranuclear Lanthanide Complexes across the Lanthanide Series: A Compendium

Acetato-bridged palladium–lanthanide tetranuclear heterometallic complexes of the form [Pd₂Ln₂(H₂O)₂(CH₃COO)₁₀] ⋅ 2 CH₃COOH [Ln₂=Ce₂ ( 1 ), Pr₂ ( 2 ), Nd₂ ( 3 ), Sm₂ ( 4 ), Tb₂ ( 5 ), Dy₂ ( 6 ), Dy_0.2Y_1.8 ( 6′′ ), Ho₂ ( 7 ), Er₂ ( 8 ), Er_0.24Y_1.7 ( 8′′ ), Tm₂ ( 9 ), Yb₂ ( 10 ), Y₂( 11 )] were synthesised and characterised by experimental and theoretical techniques. All complexes containing Kramers lanthanide ions [Ln³⁺=Ce ( 1 ), Nd ( 3 ), Sm ( 4 ), Dy ( 6 ), DyY ( 6′′ ), Er ( 8 ), ErY ( 8′′ ), Yb ( 10 )] showed field-induced slow magnetic relaxation, characteristic of single-molecule magnetism and purely of molecular origin. In contrast, all non-Kramers lanthanide ions [Ln³⁺=Pr ( 2 ), Tb ( 5 ), Ho ( 7 ), Tm ( 9 ), Y³⁺ ( 11 ) is diamagnetic and non-lanthanide] did not show any slow magnetic relaxation. The variation in the electronic structure and accompanying consequences across the complexes representing all Kramers and non-Kramers lanthanide ions were investigated. The origin of the magnetic properties and the extent to which the axial donor–acceptor interaction involving the lanthanide ions and an electron-deficient orbital of palladium affects the observed magnetic and electronic properties across the lanthanide series are presented. Unique consistent electronic and magnetic properties of isostructural complexes spanning the lanthanide series with properties dependent on whether the ions are Kramers or non-Kramers are reported.     

Synthesis,structure and luminescence properties of two novel lanthanide complexes with 2-fluorobenzoic acid and 1,10-phenanthroline

Two lanthanide complexes with 2-fluorobenzoate (2-FBA) and 1,10-phenanthroline (phen) were synthesized and characterized by X-ray diffraction. The structure of each complex contains two non-equivalent binuclear molecules, [Ln(2-FBA)₃?·?phen?·?CH₃CH₂OH]₂ and [Ln(2-FBA)₃?·?phen]₂ (Ln?=?Eu (1) and Sm (2)). In [Ln(2-FBA)₃?·?phen?·?CH₃CH₂OH]₂, the Ln³⁺ is surrounded by eight atoms, five O atoms from five 2-FBA groups, one O atom from ethanol and two N atoms from phen ligand; 2-FBA groups coordinate Ln³⁺ with monodentate and bridging coordination modes. The polyhedron around Ln³⁺ is a distorted square-antiprism. In [Ln(2-FBA)₃?·?phen]₂, the Ln³⁺ is coordinated by nine atoms, seven O atoms from five 2-FBA groups and two N atoms of phen ligand; 2-FBA groups coordinate Ln³⁺ ion with chelating, bridging and chelating-bridging three coordination modes. The polyhedron around Ln³⁺ ion is a distorted, monocapped square-antiprism. The europium complex exhibits strong red fluorescence from ⁵D₀?→?⁷F _j ( j?=?1–4) transition emission of Eu³⁺.     

Two 3D network complexes of Y(III) and Ce(III) with 2-fold interpenetration and reversible desorption-adsorption behavior of lattice water

Two novel inorganic-organic 3D network, namely{[Ln(L)_1.5(H₂O)₂]·5H₂O}n [Ln=Y (1), Ce (2)] [Ln(L)_1.5(H₂O)₂]·5H₂O [Ln=Y (1), Ce (2)], have been prepared through the assembly of the ligand 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane (H₂L) and lanthanide (III) salts under hydrothermal condition and structurally characterized by single-crystal X-ray diffractions. In complexes 1 and 2, the L²⁻ anions adopt three different coordination fashions (bidentate chelate, bidentate bridging and bidentate chelate bridging) connecting Ln(III) ions via the oxygen atoms from carboxylate moieties. Both 1 and 2 exhibit 3D network structures with 2-fold interpenetration. Interestingly, the reversible desorption-adsorption behavior of lattice water is significantly observed in the two compounds. The result shows their potential application as late-model water absorbent in the field of adsorption material.     

Synthesis,structures and fluorescent properties of two novel lanthanide [Ln = Ce(III), Pr(III)] coordination polymers based on 1,3-benzenedicarboxylate and 2-(4-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline ligands

Two structurally diverse coordination polymers [Ce₂(m-BDC)₂(m-HBDC)₂(MOPIP)₂·3/2H₂O]_n (1) and [Pr₂(m-BDC)₃(MOPIP)₂·H₂O]_n(2) have been synthesized by hydrothermal reaction of lanthanide chloride with mixed ligands benzene-1,3-dicarboxylic acid and 2-(4-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (MOPIP). The crystal structures of the complexes are zipper-like chains of octacoordinate Ln³⁺ ions, in which Ln³⁺ ions are bridged in different coordination modes by m-BDC²⁺ and decorated by MOPIP ligands. These chains are further assembled into three-dimensional supramolecular framework by π⋯π stacking and hydrogen bonding interactions. The fluorescent property and thermal stability were also investigated. Additionally, Natural bond orbital (NBO) analysis of complex 2 shows a weak covalent interaction between the coordinated atoms and Pr³⁺ ions.     

Solvothermal syntheses, and characterization of [Ln(en)4(SbSe4)] (Ln=Ce, Pr) and [Ln(en)4]SbSe4·0.5en (Ln=Eu, Gd, Er, Tm, Yb): The effect of lanthanide contraction on the crystal structures of lanthanide selenidoantimonates(V)

Two types of lanthanide selenidoantimonates [Ln(en)₄(SbSe₄)] (Ln=Ce(1a), Pr(1b)) and [Ln(en)₄]SbSe₄·0.5en (Ln=Eu(2a), Gd(2b), Er(2c), Tm(2d), Yb(2e); en=ethylenediamine) were solvothermally synthesized by reactions of LnCl₃, Sb and Se with the stoichiometric ratio in en solvent at 140 °C. The four-en coordinated lanthanide complex cation [Ln(en)₄]³⁺ formed in situ balances the charge of SbSe₄³⁻ anion. In compounds 1a and 1b, the SbSe₄³⁻ anion act as a monodentate ligand to coordinate complex [Ln(en)₄]³⁺ and the neutral compound [Ln(en)₄(SbSe₄)] is formed. The Ln³⁺ ion has a nine-coordinated environment involving eight N atoms and one Se atom forming a distorted monocapped square antiprism. In 2a-2e the lanthanide(III) ion exists as isolated complex [Ln(en)₄]³⁺, in which the Ln³⁺ ion is in a bicapped trigonal prism geometry. A systematic investigation of the crystal structures reveals that two types of structural features of these lanthanide selenidoantimonates are related with lanthanides contraction across the lanthanide series. TG curves show that compounds 1a-1b and 2a-2e remove their organic components in one and two steps, respectively.     

Formation Thermodynamics of Binary and Ternary Lanthanide(III) Complexes with 1,10-Phenanthroline and Chloride in N,N-Dimethylformamide

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm^–3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)³⁺ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)³⁺ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)³⁺ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln³⁺-Cl^–-phen system, the formation of LnCl(phen)²⁺, LnCl₂(phen)⁺, and LnCl₃(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.