Syntheses and Crystal Structures of Mononuclear and Binuclear Lanthanide Halide Complexes with Diglyme

Two types of isostructural complexes of lanthanide chlorides with diglyme have been synthesized. These are mononuclear molecular complexes [LnCl₃(diglyme)(THF)] (Ln = Eu ( 1 ), Gd ( 2 ), Dy ( 3 ), Er ( 4 ), Yb ( 5 ); diglyme = diethylen glycol dimethyl ether) and binuclear molecular complexes [LnCl₃(diglyme)]₂ (Ln = Dy ( 3d ), Er ( 4d ), Yb ( 5d )). Complex 1 was obtained by the reaction of [EuCl₃(DME)₂] with diglyme in THF. The complexes 2 – 5 and 3d – 5d resulted from reactions of LnCl₃·6H₂O, (CH₃)₃SiCl and diglyme in THF. The mononuclear complexes 2 – 5 crystallized directly from the solutions where the reactions of lanthanide compounds with diglyme took place. Recrystallizations of the powder products of the same reactions from dichloromethane resulted in the binuclear complexes 3d – 5d . Reactions of lanthanide bromide hydrates, (CH₃)₃SiBr and diglyme in THF achieved mononuclear molecular complexes [LnBr₃(diglyme)(L)] (Ln = Gd, L = H₂O ( 6 ); Ln = Ho, L = THF ( 7 )). Crystals of 6 and 7 were grown by recrystallization from dichloromethane. The lanthanide atoms (Ln = Eu–Yb) are seven‐coordinated in a distorted pentagonal bipyramidal fashion in all reported complexes, 1 – 7 and 3d – 5d . Four oxygen atoms and three halide ions are coordinated to lanthanide atoms in 1 – 7 , [LnX₃(diglyme)(L)]. Four chloride ions, two bridging and two nonbridging, and three oxygen atoms are coordinated to lanthanide atoms in 3d – 5d , [LnCl₃(diglyme)]₂.     

Novel Lanthanide (III) Complexes Derived from an Imidazole–Biphenyl–Carboxylate Ligand: Synthesis,Structure and Luminescence Properties

A series of neutral mononuclear lanthanide complexes [Ln(HL)₂(NO₃)₃] (Ln = La, Ce, Nd, Eu, Gd, Dy, Ho) with rigid bidentate ligand, HL (4′-(1H-imidazol-1-yl)biphenyl-4-carboxylic acid) were synthesized under solvothermal conditions. The coordination compounds have been characterized by infrared spectroscopy, thermogravimetry, powder X-ray diffraction and elemental analysis. According to X-ray diffraction, all the complexes are a series of isostructural compounds crystallized in the P2/n monoclinic space group. Additionally, solid-state luminescence measurements of all complexes show that [Eu(HL)₂(NO₃)₃] complex displays the characteristic emission peaks of Eu(III) ion at 593, 597, 615, and 651 nm.     

NMR Characterization of Lanthanide(3+) Complexes of Tetraazatetrakisphosphinato and Tetraazatetra­kisphosphonato Ligands

The three‐dimensional structures in aqueous solution of the entire series of the Ln³⁺ complexes [Ln(DOTP*‐Et)]^? (formed from the free ligand P,P′,P″,P′′′‐[1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrayltetrakis(methylene)]tetrakis[P‐ethylphosphinic acid] (H₄DOTP*‐Et) were studied by NMR techniques to rationalize the parameters governing the relaxivity of the Gd³⁺ complex and evaluate its potential as MRI contrast agent. From the ¹H‐ and ³¹P‐NMR lanthanide‐induced‐shift (LIS) values, especially of the [Yb(DOTP*‐Et)]^? complex, it was concluded that the [Ln(DOTP*‐Et)]^? complexes adopt in solution twisted square antiprismatic coordination geometries which change gradually their coordination‐cage structure along the lanthanide series. These complexes have no inner‐sphere‐H₂O coordination, and preferentially have the (R,R,R,R) configuration of the P‐atoms in the pendant arms. Self‐association was observed in aqueous solution for the tetraazatetrakisphosphonic acid ester complexes [Ln(DOTP*‐OEt)]^? (=[Ln(DOTP‐Et)]^?) and [Ln(DOTP*‐OBu)]^? (=[Ln(DOTP‐Bu)]^?) at and above 5 mM concentration, through analysis of ³¹P‐NMR, EPR, vapor‐pressure‐osmometry, and luminescence‐spectroscopic data. The presence of the cationic detergent cetylpyridinium chloride (CPC; but not of neutral surfactants) shifts the isomer equilibrium of [Eu(DOTP*‐OBu)]^? to the (S,S,S,S) form which selectively binds to the cationic micelle surface.     

模板分子诱导的微孔镧系-2-羧基肉桂酸超分子配合物的合成与结构

由水热法合成了2个微孔镧系超分子配合物[Ln(CCA)(OH)(phen)(H2O)]n·n(phen)·nH2O(Ln=Yb,1;Er,2;H2CCA=2-羧基肉桂酸;phen=1,10-菲啰啉),并用元素分析、IR及X-射线单晶衍射对其进行了表征。晶体结构研究表明,2个配合物都是由配体2-羧基肉桂酸连接而形成的一维双链结构,该链状结构通过氢键和π-π堆积作用扩展为具有微孔结构的超分子。1,10-菲啰啉在微孔结构的形成过程中起到了模板剂的作用。     

Potentiometric Study of Lanthanide Salicylaldimine Schiff Base Complexes

Formation of complexes between the lanthanide ions and N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand was studied in solution by pH potentiometry. The potentiometric titration was performed at 25.00 °C in 0.1 mol·dm^?3 NaClO₄ ionic strength and in DMSO:water (30:70 v:v) solvent mixture. N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand (H₂L) occurs in three forms: fully or partially deprotonated and unionized. Computer analysis of potentiometric data indicated that in solution the lanthanide (Ln) complexes exist as LnL₂, Ln(HL)₂ and Ln(H₂L)₂ species. This observation appears to be in contrast to the solid-state behavior of these complexes prepared in a self-assembly process and structurally defined. Stability constants for La³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Ho³⁺ and Lu³⁺ (Ln³⁺) complexes were determined. The order of stabilities of LnL₂ species in terms of metal ions is La³⁺ > Eu³⁺ ≈ Gd³⁺ = Tb³⁺ < Ho³⁺ < Lu³⁺ with a prominent “gadolinium break”.     

两个镧系金属配合物的水热合成、晶体结构、荧光、热稳定性及抑菌活性

水热法合成了2个镧系配合物[Ln(3,4-DFBA)₃(phen)(H₂O)]₂(H₂O)₂(Ln=Sm (1),Ho (2);3,4-DFBA=3,4-二氟苯甲酸, phen=菲咯啉)。利用X-射线单晶衍射仪测定了配合物的晶体结构。配合物1和2结构相同,配位数为8,属于三斜晶系,空间群为P1。相邻的2个双核分子之间通过分子间氢键作用形成了2D层状结构。并用元素分析,红外,紫外,XRD等手段对目标配合物进行了表征。用TG-DTG技术测定了配合物的热稳定性,同时对配合物1的荧光性能进行了研究。另外,还测定了这两种配合物对白色念珠菌,革兰氏阳性菌(大肠杆菌)以及革兰氏阴性菌(金黄色葡萄球菌)的抑菌活性。     

Syntheses and Crystal Structures of Lanthanide Chloride Complexes with Diglyme

Reactions of [LnCl₃(DME)₂] (Ln = Nd, Sm, Ho, Lu; DME = dimethoxyethane) and diglyme (diglyme = diethylen glycol dimethyl ether) in THF resulted in polymeric [LnCl₃(diglyme)]_n (Ln = Nd ( 1 ), Sm ( 2 )) or mononuclear complexes [LnCl₃(diglyme)(THF)] (Ln = Ho ( 3 ), Lu ( 4 )). Neodymium and samarium atoms in 1 and 2 are eight‐coordinated by three oxygen atoms from diglyme, one terminal and four bridging chloride ions. Holmium and lutetium atoms in 3 and 4 are seven‐coordinated by three oxygen atoms from diglyme, three chloride ions and one oxygen atom from THF. [ErCl₃(diglyme)(H₂O)] ( 5 ) resulted from the reaction of ErCl₃·6H₂O, (CH₃)₃SiCl and diglyme in THF. The molecular structures of 3 , 4 and 5 are similar, with either a molecule of THF coordinated to the lanthanide atom in 3 and 4 or with a molecule of water coordinated in 5 .     

两个双核稀土-自由基化合物的合成、结构及磁性

以乙酰丙酮为共配体的稀土配合物与2-羟基苯取代的自由基配体进行反应得到2个新颖的稀土-自由基配合物[Ln₂（acac）₄（NIT-PhO）₂]（Ln=Tb（1）,Y（2）;acac=乙酰丙酮,NIT-PhOH=2-（2''-hydroxyphenyl）-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide）。2个配合物的结构相同,均是通过2个自由基配体上的羟基氧原子桥联2个稀土离子构成双核结构。直流磁化率的研究表明配合物2具有弱的反铁磁性质。     

两个氮氧双自由基桥连的稀土一维链的晶体结构、磁性和荧光性能

选用1,2-二苯氧基乙烷取代的氮氧双自由基（BNPhOEt）与稀土金属反应,得到了2例氮氧双自由基-稀土配合物[Ln（hfac）₃（BNPhOEt）]·C₆H₁₄（Ln=Tb（1）、Ho（2）;hfac=六氟乙酰丙酮）,其均为2p-4f一维链状结构。磁性研究表明,在配合物1和2中分别存在铁磁和反铁磁耦合。此外,对2个配合物的荧光光谱进行了研究分析。     

Remarkable Tuning of the Coordination and Photophysical Properties of Lanthanide Ions in a Series of Tetrazole‐Based Complexes

A series of seven new tetrazole‐based ligands (L1, L3–L8) containing terpyridine or bipyridine chromophores suited to the formation of luminescent complexes of lanthanides have been synthesized. All ligands were prepared from the respective carbonitriles by thermal cycloaddition of sodium azide. The crystal structures of the homoleptic terpyridine–tetrazolate complexes [Ln(Li)₂]NHEt₃ (Ln=Nd, Eu, Tb for i=1, 2; Ln=Eu for i=3, 4) and of the monoaquo bypyridine–tetrazolate complex [Eu(H₂O)(L7)₂]NHEt₃ were determined. The tetradentate bipyridine–tetrazolate ligand forms nonhelical complexes that can contain a water molecule coordinated to the metal. Conversely, the pentadentate terpyridine–tetrazolate ligands wrap around the metal, thereby preventing solvent coordination and forming chiral double‐helical complexes similarly to the analogue terpyridine–carboxylate. Proton NMR spectroscopy studies show that the solid‐state structures of these complexes are retained in solution and indicate the kinetic stability of the hydrophobic complexes of terpyridine–tetrazolates. UV spectroscopy results suggest that terpyridine–tetrazolate complexes have a similar stability to their carboxylate analogues, which is sufficient for their isolation in aerobic conditions. The replacement of the carboxylate group with tetrazolate extends the absorption window of the corresponding terpyridine‐ (≈20 nm) and bipyridine‐based (25 nm) complexes towards the visible region (up to 440 nm). Moreover, the substitution of the terpyridine–tetrazolate system with different groups in the ligand series L3–L6 has a very important effect on both absorption spectra and luminescence efficiency of their lanthanide complexes. The tetrazole‐based ligands L1 and L3–L8 sensitize efficiently the luminescent emission of lanthanide ions in the visible and near‐IR regions with quantum yields ranging from 5 to 53 % for Eu^III complexes, 6 to 35 % for Tb^III complexes, and 0.1 to 0.3 % for Nd^III complexes, which is among the highest reported for a neodymium complex. The luminescence efficiency could be related to the energy of the ligand triplet states, which are strongly correlated to the ligand structures.     

Synthesis,Structures, and Luminescent Properties of Chloride and Nitrate LnIII Complexes Coordinated by tris(Pyrazolyl)methane

We report the synthesis of Ln³⁺ nitrate [Ln(Tpm)(NO₃)₃] ⋅ MeCN (Ln=Yb ( 1Yb ), Eu ( 1Eu )) and chloride [Yb(Tpm)Cl₃] ⋅ 2MeCN ( 2Yb ), [Eu(Tpm)Cl₂(μ-Cl)]₂ ( 2Eu ) complexes coordinated by neutral tripodal tris(3,5-dimethylpyrazolyl)methane (Tpm). The crystal structures of 1Ln and 2Ln were established by single crystal X-ray diffraction, while for 1Yb high resolution experiment was performed. Nitrate complexes 1Ln are isomorphous and both adopt mononuclear structure. Chloride 2Yb is monomeric, while Eu³⁺ analogue 2Eu adopts a binuclear structure due to two μ²-bridging chloride ligands. The typical lanthanide luminescence was observed for europium complexes ( 1Eu and 2Eu ) as well as for terbium and dysprosium analogues ([Ln(Tpm)(NO₃)₃] ⋅ MeCN, Ln=Tb ( 1Tb ), Dy ( 1Dy ); [Ln(Tpm)Cl₃] ⋅ 2MeCN, Ln=Tb ( 2Tb ), Dy ( 2Dy )).     

Water Stability and Luminescence of Lanthanide Complexes of Tripodal Ligands Derived from 1,4,7‐Triazacyclononane: Pyridinecarboxamide versus Pyridinecarboxylate Donors

A series of europium(III) and terbium(III) complexes of three 1,4,7‐triazacyclononane‐based pyridine containing ligands were synthesized. The three ligands differ from each other in the substitution of the pyridine pendant arm, namely they have a carboxylic acid, an ethylamide, or an ethyl ester substituent, i.e., these ligands are 6,6′,6″‐[1,4,7‐triazacyclononane‐1,4,7‐triyltris(methylene)]tris[pyridine‐2‐carboxylic acid] (H₃tpatcn), ‐tris[pyridine‐2‐carboxamide] (tpatcnam), and ‐tris[pyridine‐2‐carboxylic acid] triethyl ester (tpatcnes) respectively. The quantum yields of both the europium(III) and terbium(III) emission, upon ligand excitation, were highly dependent upon ligand substitution, with a ca. 50‐fold decrease for the carboxamide derivative in comparison to the picolinic acid (=pyridine‐2‐carboxylic acid) based ligand. Detailed analysis of the radiative rate constants and the energy of the triplet states for the three ligand systems revealed a less efficient energy transfer for the carboxamide‐based systems. The stability of the three ligand systems in H₂O was investigated. Although hydrolysis of the ethyl ester occurred in H₂O for the [Ln(tpatcnes)](OTf)₃ complexes, the tripositive [Ln(tpatcnam)](OTf)₃ complexes and the neutral [Ln(tpatcn)] complexes showed high stability in H₂O which makes them suitable for application in biological media. The [Tb(tpatcn)] complex formed easily in H₂O and was thermodynamically stable at physiological pH (pTb 14.9), whereas the [Ln(tpatcnam)](OTf)₃ complexes showed a very high kinetic stability in H₂O, and once prepared in organic solvents, remained undissociated in H₂O.     

Hexamethylphosphoramide Compounds: I. Preparation and Characterisation of Lanthanide Perrhenate Complexes

Abstract

Compounds with composition [Ln (ReO₄₎₂ (HMPA)₂] ReO₄ (Ln=La Nd) and [Ln(ReO₄₎₂(HMPA)₄]ReO₄ (Ln=Sm-Lu, Y) were synthesized by reaction of HMPA with the hydrated lanthanide perrhenate in ethanol followed by triethyl-orthoformate precipitation. The compounds from lanthanum to gadolinium are soluble enough and behave as 1:1 electrolytes in methanol. The remaining behave as 1:1 electrolytes in nitromethane and acetonitrile. Two types of IR spectra were observed, corresponding to the two different compositions. In all cases bands attributed to ionic and solittings due to coordinated bidentate perrhenate for the lighter and mono dentate for the heavier ones were observed. Splittings and shifts of VPO could arise from at least two non-equivalent PO groups. The band at -1190 or 1180 cm^?1 (m) is attributed to a weakly bonded and that at 1125 cm^?1 (m) to a strongly bonded, through the phosphoryl oxygen. The v as P-N-C and v _s P-N-C bands are shifted to higher frequencies as compared to the free ligand. The absorption spectra of the neodymium compound in the hypersensitive ⁴G_5/2, ²G_7/2 ← ⁴I_9/2 transition region were determined. The experimental data permit us to conclude that Nd³⁺ ions are not located in a cubic site. The nephelauxetic parameter, covalent factor and Sinha's parameter indicate an appreciable covalent character of the ligands: Nd³⁺ interaction. (CNPq, FAPESP, FINEP).     

Highly Efficient Visible‐to‐NIR Luminescence of Lanthanide(III) Complexes with Zwitterionic Ligands Bearing Charge‐Transfer Character: Beyond Triplet Sensitization

Two zwitterionic‐type ligands featuring π–π* and intraligand charge‐transfer (ILCT) excited states, namely 1,1′‐(2,3,5,6‐tetramethyl‐1,4‐phenylene)bis(methylene)dipyridinium‐4‐olate (TMPBPO) and 1‐dodecylpyridin‐4(1 H)‐one (DOPO), have been prepared and applied to the assembly of lanthanide coordination complexes in an effort to understand the ligand‐direction effect on the structure of the Ln complexes and the ligand sensitization effect on the luminescence of the Ln complexes. Due to the wide‐band triplet states plus additional ILCT excitation states extending into lower energy levels, broadly and strongly sensitized photoluminescence of f→f transitions from various Ln³⁺ ions were observed to cover the visible to near‐infrared (NIR) regions. Among which, the Pr, Sm, Dy, and Tm complexes simultaneously display both strong visible and NIR emissions. Based on the isostructural feature of the Ln complexes, color tuning and single‐component white light was achieved by preparation of solid solutions of the ternary systems Gd‐Eu‐Tb (for TMPBPO) and La‐Eu‐Tb and La‐Dy‐Sm (for DOPO). Moreover, the visible and NIR luminescence lifetimes of the Ln complexes with the TMPBPO ligand were investigated from 77 to 298 K, revealing a strong temperature dependence of the Tm³⁺ (³H₄) and Yb³⁺ (²F_5/2) decay dynamics, which has not been explored before for their coordination complexes.     

Vibrational Quenching in Near-Infrared Emitting Lanthanide Complexes: A Quantitative Experimental Study and Novel Insights

Two series of novel NIR-emissive complexes of Nd³⁺, Sm³⁺, Er³⁺ and Yb³⁺ with two different β-diketonate ligands (L₁=4,4,4-trifluoro-1-phenyl-1,3-butadione and L₂=4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadione) are reported. The neutral triphenylphosphine oxide (tppo) ligand was used to replace coordinated water molecules in the first coordination sphere of the as-obtained [Ln(L₁₍₂₎)₃(H₂O)₂] complexes to afford water-free [Ln(L₁₍₂₎)₃(tppo)₂] molecular species. Upon replacement of water molecules by tppo units, the NIR emission lifetimes of the Nd³⁺, Er³⁺and Sm³⁺complexes increase by about one order of magnitude up to values of ≈9, 8 and 113 ms while Yb³⁺ complexes reach intrinsic quantum yields as high as to Φ_Yb=6.5 %., which are remarkably high for fully hydrogenated complexes. Vibrational quenching by CH and OH oscillators has been quantitatively assessed by implementing the Förster's model of resonance energy transfer on the basis of experimental data. This study demonstrates that highly efficient NIR-emitting lanthanide complexes can be obtained with facile, cheap and accessible syntheses through a rational design.     

Synthesis,Charactarization and Crystal Structures of Lanthanide Phenoxyacetate Complexes with1,10—Phenanthroline

Three new lanthanide phenoxyacetate complexes with 1,10‐phenanthroline. [Nd(POA)₃ (phen)]₂ · 2C₂H₅OH (1), [Eu(POA)₃‐ (phen)]₂ · 2C₂H₅OH (2) and [Sm(POA)₂(DMSO)(phen)]₂‐ (ClO₄)₂ (3) (POA= phenoxyacetate, phen = 1,10‐phenanthroline, DMSO = dimethyl sulfoxide), were synthesized and characterized by elemental analyses, IR, UV‐vis and FAB‐MS spectra. Their structures were determined by single crystal X‐ray diffraction analysis. In complexes 1 and 2, the carboxylate groups are bonded to Ln³⁺ ion in three modes: the chelating bidentate, the bridging bidentate and the bridging tridentate. In complex 3, the carboxylate groups are bonded to Sm³⁺ ion only involved in one mode: the bridging bidentate. The luminescence behavior of complex 2 was also studied by means of emission spectra.     

Lanthanide complexes of D-penicillamine: formation constants,spectral and thermal properties

The complex-formation of lanthanide(III) elements with D-penicillamine have been investigated in acidic and neutral media. The macroscopic protonation constants of the ligand and the formation constants of [Ln.Pen]⁺, [Ln.Pen₂]^?, [Ln.Pen.OH] and [Ln.Pen.(OH)₂]^? complexes were determined from pH-metric data using the BEST computer program. Elemental analyses of the solid complexes indicate formation of 1?:?1 metal?:?ligand species. The binding sites in the complexes with the possible role of –COO^?, –NH₂ and –SH groups in the coordination have been discussed using infrared data. The complexes decompose in four steps as shown by their t.g. and d.t.a. analyses. A mechanism of decomposition is proposed which is supported by mass spectral data.     

Synthesis,Characterization, Antimicrobial Activities,and Structural Studies of Lanthanide (III) Complexes with 1-(4-Chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1-thiosemicarbazone

Twelve coordinate lanthanide (III) complexes with the general composition [Ln L₃X_n(H₂O)_n] where Ln = Pr(III), Sm(III), Eu (III), Gd (III), Tb (III), Dy (III), X = Cl^?1, NO₃ ^?2, n = 2–7, and L is 1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1- thiosemicarbazone have been prepared. The lanthanide complexes (5) were derived from the reaction between 1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1-thiosemicarbazone (4) with an aqueous solution of lanthanide salt. Chalcone thiosemicarbazone ligand (4) was prepared by the reaction of [1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)]prop-2-enone (chalcone) (3) with thiosemicarbazide in the presence of hot ethanol. All the lanthanide-ligand 1:3 complexes have been isolated in the solid state, are stable in air, and characterized on the basis of their elemental and spectral data.

Thiosemicarbazone ligands behave as bidentate ligands by coordinating through the sulfur of the isocyanide group and nitrogen of the cyanide residue. The probable structure for all the lanthanide complexes is also proposed. The chalcone thiosemicarbazone ligands and their lanthanide complexes have been screened for their antifungal and antibacterial studies. Some of the synthesized lanthanide complexes have shown enhanced activity compared with that of the free ligand.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Liquid-Crystalline and Orientation Properties of Lanthanide Complexes with β-Enaminoketone

A series of liquid-crystalline lanthanide complexes with 1-(4-dodecyloxyphenyl)-3-octadecylamino-2-propene-1-one (HL), which is substituted β-enaminoketone, with the composition Ln(HL)₃(NO₃)₃ (Ln = La, Nd, Gd, Tb, Dy, Ho, and Er) is synthesized. For the most part of the synthesized complexes, the magnetic susceptibility anisotropy (Δχ_min) is shown to be one to two orders higher than Δχ of the “classical” organic liquid crystals.     

Spectrofluorimetric Study of the Complexes Between Calcein and Lanthanide(III) Ions

ABSTRACT

The equilibrium of calcein, an H6L type fluorescent ligand, with lanthanide(III) ions, Ln(III), was studied spectrofluorimetrically in aqueous solution at constant ionic strength =0.1 (KC1), pH 8.0 and 25.0±0.1°C. Application of the mole ratio and continuous variation methods reveals the formation of 1:1 complexes. The conditional stability constants (β') were calculated from the analysis of the observed fluorescence vs. [Ln(III)]/[calcein] mole ratio data by using an iterative non-linear least-squares computer program. The values obtained for β' are in the range 5.24×10⁶-5.77×10⁷ The thermodynamic stability constant (β) were estimated by calculating the sidereaction coefficients (α) fro lanthanides and calcein. The β values obtained were from 3.2×10¹² to 3.6×10¹³