Lanthanide Perchlorates Research Articles

Understanding the Mechanism of Gelation and Stimuli-Responsive Nature of a Class of Metallo-Supramolecular Gels

Utilizing metal-ligand binding as the driving force for self-assembly of a ditopic ligand, which consists of a 2,6-bis-(1'-methylbenzimidazolyl)-4-oxypyridine moiety attached to either end of a penta(ethylene glycol) core, in the presence of a transition metal ion (Zn(II)) and a lanthanide metal ion (La(III)), we have achieved formation of stimuli-responsive metallo-supramolecular gels. We describe herein a series of experimental studies, including optical and confocal microscopy, dynamic light scattering, wide-angle X-ray diffraction, and rheology, to explore the properties of such gels, as well as the nature of the gelation mechanism. Morphological and X-ray diffraction observations suggest gelation occurs via the flocculation of semicrystalline colloidal particles, which results in the gels exhibiting pronounced yielding and thixotropic behavior. Application of mechanical stress results in a decrease in the particle size, which is accompanied by an increase in gel strength after removal of the stress. Moreover, studies show that the presence of lanthanide(III) perchlorate increases the mechano-responsiveness of the gels, as a consequence of reduced crystallinity of the colloidal particles, presumably due to the different coordination ability of lanthanide(III) and zinc(II), which changes the nature of the self-assembly in these materials.

Apparent molar volumes and apparent molar heat capacities of Pr(NO 3) 3(aq), Gd(NO 3) 3(aq), Ho(NO 3) 3(aq), and Y(NO 3) 3(aq) at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa

Relative densities and relative massic heat capacities have been measured for acidified solutions of Y(NO 3) 3(aq), Pr(NO 3) 3(aq), and Gd(NO 3) 3(aq) at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa. In addition, relative densities and massic heat capacities have been measured at the same temperatures and pressure for Y(NO 3) 3(aq) and Ho(NO 3) 3(aq) solutions without excess acid (n.b. measurements at T = 328.15 K for Ho(NO 3) 3(aq) were not performed due to the limited volume of solution available). Apparent molar volumes and apparent molar heat capacities for the aqueous salt solutions have been calculated from the experimental apparent molar properties of the acidified solutions using Young’s rule, whereas the apparent molar properties of the solutions without excess acid were calculated directly from the measured densities and massic heat capacities. The two sets of data for the Y(NO 3) 3(aq) systems provide a check of the internal consistency of the Young’s rule approach we have utilised. The concentration dependences of the apparent molar volumes and heat capacities of the aqueous salt solutions have been modelled at each investigated temperature using the Pitzer ion interaction equations to yield apparent molar properties at infinite dilution. Complex formation within the aqueous rare earth nitrate systems is discussed qualitatively by probing the concentration dependence of apparent molar volumes and heat capacities. In spite of the complex formation in the aqueous rare earth nitrate systems, there is a high degree of self-consistency between the apparent molar volumes and heat capacities at infinite dilution reported in this manuscript and those previously reported for aqueous rare earth perchlorates.

Apparent molar heat capacities and apparent molar volumes of Pr(ClO 4) 3(aq), Gd(ClO 4) 3(aq), Ho(ClO 4) 3(aq), and Tm(ClO 4) 3(aq) at T=(288.15, 298.15, 313.15, and 328.15) K and p=0.1 MPa

Acidified aqueous solutions of Pr(ClO 4) 3(aq), Gd(ClO 4) 3(aq), Ho(ClO 4) 3(aq), and Tm(ClO 4) 3(aq) were prepared from the corresponding oxides by dissolution in dilute perchloric acid. Once characterized with respect to trivalent metal cation and acid content, the relative densities of the solutions were measured at T=(288.15, 298.15, 313.15, and 328.15) K and p=0.1 MPa using a Sodev O2D vibrating tube densimeter. The relative massic heat capacities of the aqueous systems were also determined, under the same temperature and pressure conditions, using a Picker Flow Microcalorimeter. All measurements were made on solutions containing rare earth salt in the concentration range 0.01 ⩽ m/(mol · kg −1) ⩽ 0.2. Relative densities and relative massic heat capacities were used to calculate the apparent molar volumes and apparent molar heat capacities of the acidified salt solutions from which the apparent molar properties of the aqueous salt solutions were extracted by the application of Young's Rule. The concentration dependences of the isothermal apparent molar volumes and heat capacities of each aqueous salt solution were modelled using Pitzer ion-interaction equations. These models produced estimates of apparent molar volumes and apparent molar heat capacities at infinite dilution for each set of isothermal V φ,2 and C p φ,2 values. In addition, the temperature and concentration dependences of the apparent molar volumes and apparent molar heat capacities of the aqueous rare earth perchlorate salt solutions were modelled using modified Pitzer ion-interaction equations. The latter equations utilized the Helgeson, Kirkham, and Flowers equations of state to model the temperature dependences (at p=0.1 MPa) of apparent molar volumes and apparent molar heat capacities at infinite dilution. The results of the latter models were compared to those previously published in the literature. Apparent molar volumes and apparent heat capacities at infinite dilution for the trivalent metal cations Pr 3+(aq), Gd 3+(aq), Ho 3+(aq), and Tm 3+(aq) were calculated using the conventions V 2 ∘(H +(aq)) ≡ 0 and C p2 ∘(H +(aq)) ≡ 0 and have been compared to other values reported in the literature.

Synthesis and calorimetric study of rare earth complexes [RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3 (RE: Sm, Eu, Dy, Er)

The crystals of four complexes of rare earth perchlorate with dl-α-alanine and imidazole were synthesized and characterized. The components of them were determined to be [RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3 (RE: Sm, Eu, Dy, Er) by FT-IR, chemical, elemental and thermal analysis. The enthalpies of dissolution of [2C 3H 7NO 2(s) + 3NaClO 4(s)], [C 3H 4N 2(s) + RECl 3·6H 2O(s)] and [3NaCl(s)], {[RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3(s)} were determined by a solution–reaction isoperibol calorimeter at T=298.15 K, respectively. According to Hess’s law, the standard molar enthalpies of reaction of four reactions, RECl 3·6H 2O(s) + 2C 3H 7NO 2(s) + C 3H 4N 2(s) + 3NaCl(s) = [RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3(s) + 3NaCl(s) + 5H 2O(l) (RE: Sm, Eu, Dy, Er) were determined to be 4.87±0.20, 7.23±0.19, 0.96±0.27 and 12.88±0.32 kJ mol −1, respectively. The standard molar enthalpies of formation of the four complexes at T=298.15 K, Δ f H m Θ {[Re(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3(s)} (RE: Sm, Eu, Dy, Er), were determined to be −(2448.1±3.3), −(2360.3±3.3), −(2451.8±3.3) and −(2444.3±3.3) kJ mol −1, respectively.

Lanthanide perchlorate complexes with 1,4-bis(phenylsulfinyl)butane: structures and luminescent properties

Five representative lanthanide coordination compounds with a disulfoxide ligand [L = 1,4-bis(phenylsulfinyl)butane], [Ln(L)4](ClO4)3 (Ln = La, 1; Eu, 2; Gd, 3; Tb, 4; Yb, 5), have been synthesized and structurally characterized by single-crystal X-ray diffraction. These compounds have isostructural mononuclear structures, in which the ligand L coordinates to the metal ions through O donors in chelating coordination mode. The luminescence studies of 2 and 4 in the solid state and solution exhibit the usual metal-centred emission spectra arising from ligand-to-metal energy transfer, and their intensity and lifetimes are increased compared to those of previously reported analogous complexes {[Ln(L)2(DMF)4](ClO4)3·nH2O}∝ (Ln = Eu, n = 4, 6; Ln = Tb, n = 3, 7). The stability of these complexes in solution was also investigated.

Crystal Structure of LiClO4.

Single crystals of LiClO4 were obtained during attempts to prepare lithium containing rare earth perchlorates from a lithium perchlorate melt. In the crystal structure of LiClO4 (ortho-rhombic, Pnma, Z =4, a = 865.7(1), b = 691.29(9) pm, c = 483.23(6), Rall = 0.0273) the Li+ ions are in distorted octahedral coordination of oxygen atoms. The octahedra are linked via common edges to chains according to 1[LiO2/1O4/2] which run in the [010] direction. The perchlorate ions are almost ideal tetrahedra.

Crystal Structure of LiClO4

AbstractSingle crystals of LiClO4 were obtained during attempts to prepare lithium containing rare earth perchlorates from a lithium perchlorate melt. In the crystal structure of LiClO4 (ortho‐rhombic, Pnma, Z =4, a = 865.7(1), b = 691.29(9) pm, c = 483.23(6), Rall = 0.0273) the Li+ ions are in distorted octahedral coordination of oxygen atoms. The octahedra are linked via common edges to chains according to 1[LiO2/1O4/2] which run in the [010] direction. The perchlorate ions are almost ideal tetrahedra.

Lanthanide(III) perchlorate complexes of two 24 membered N 3O 4-donor macrocycles

Two novel macrocycles, L 1 and L 2, containing a N 3O 4-donor set, have been synthesised, and their complexation potential towards Ln(III) ions have been investigated. The cyclocondensation reaction between 2,6-bis(2-formylphenoxymethyl)pyridine and 1,2-bis(2-aminophenoxy)butane in the absence of metal ions, yields the macrocycle L 1 as the main product. The diamine macrocycle L 2 is formed by reaction of the diamine and dicarbonyl precursors followed by an in situ reduction with NaBH 4. The interaction of lanthanide(III) ions with both ligands has been investigated.

Phosphodiester hydrolysis by lanthanide complexes of bis-tris propane.

Potentiometric titrations of the mixtures of lanthanide(III) perchlorates and bis-Tris propane (BTP) reveal formation of dinuclear hydroxo complexes M2(BTP)2(OH)n(6-n), where M = La(III), Pr(III), Nd(III), Eu(III), Gd(III), and Dy(III) and n = 2, 4, 5, or 6, in the pH range 7-9. ESI-MS data confirm the presence of dinuclear species. Kinetics of the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP), mono-4-nitrophenyl phosphate (NPP), and 4-nitrophenyl acetate (NPA) in the lanthanide(III)-BTP systems has been studied at 25 degrees C in the pH range 7-9. The second-order rate constants for the hydrolysis of BNPP by individual lanthanide hydroxo complexes have been estimated by using the multiple regression on observed rate constants obtained at variable pH. For a given metal, the rate constants increase with increasing in the number n of coordinated hydroxide ions. In a series of complexes with a given n, the second-order rate constants decrease in the order La > Pr > Nd > Eu > Gd > Dy. Hydrolysis of NPP follows Michaelis-Menten-type "saturation" kinetics. This difference in kinetic behavior can be attributed to stronger binding of NPP dianion than BNPP monoanion to the lanthanide(III) species. Activities of lanthanide complexes in the hydrolysis of NPA, which is 10(6) times more reactive than BNPP in alkaline or aqueous hydrolysis, are similar to those in BNPP hydrolysis indicating unique capability of lanthanide(III) cations to stabilize the transition state of phosphate diester hydrolysis. Results of this study are analyzed together with literature data for other metal cations in terms of the Brønsted correlation and transition state-catalyst complexation strength.

Rare earth macrocyclic complexes derived from spermine

The yttrium and lanthanide perchlorates were found to act as templates for the cyclic [1+1] condensation of 2,6-diacetylpyridine with spermine (4,9-diazadodecane-1,12-diamine) to yield 19-membered pentadentate Schiff base macrocyclic complexes with an N 5 set of donor atoms. The complexes were characterized by spectral data (IR, 1H NMR, FAB-MS), thermogravimetric and elemental analysis.

Yttrium and Lanthanide Perchlorate Complexes of N,N'-Bis(4-Antipyrylmethylidene)Ethylenediamine

Complexes of yttrium and lanthanide perchlorates with N,N'-bis(4-antipyrylmethylidene)ethylenediamine (BAME) having the general formula [Ln(BAME)2(ClO4)](ClO4)2, where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er have been synthesised and characterised by elemental analyses, molar conductance in non-aqueous solvents, electronic, infrared and proton NMR spectra as well as thennogravimetric analyses. BAME acts as a neutral bidentate ligand coordinating through both azomethine nitrogen atoms. One of the perchlorate groups is coordinated in a bidentate manner. A coordination number of six may be assigned to the metal ion in these complexes. The covalency parameters evaluated from the solid state electronic spectra suggest weak covalent character of the metal-ligand bond. The TG data of the lanthanide complexes indicate that the complexes are stable up to about 275°C and undergo decomposition in two stages forming the respective anhydrous lanthanide chloride as the final product.

Self-Assembled Dinuclear Lanthanide Helicates: Substantial Luminescence Enhancement upon Replacing Terminal Benzimidazole Groups by Carboxamide Binding Units.

The segmental ligands bis{1-alkyl-2-[6'-(N,N-diethylcarbamoyl)pyridin-2'-yl]benzimidazol-5-yl}methane (alkyl = methyl (L(5)), ethyl (L(6))) react with lanthanide perchlorates (Ln = La, Eu, Gd, Tb) in acetonitrile to yield the f-f dinuclear homotopic triple-stranded helicates [Ln(2)(L(i)())(3)](6+) (i = 5, 6) under thermodynamic control. The crystal structure of [Tb(2)(L(6))(3)](ClO(4))(3)(MeCN)(2)(THF)(0.5)(EtOH)(0.5) (11a, C(124)H(145)N(26)O(31)Cl(6)Tb(2), triclinic, P&onemacr;, Z = 2) shows the wrapping of the ligands about a pseudo-C(3) axis passing through the metal ions. The Tb ions are 9-coordinate in facial pseudo-tricapped trigonal prismatic sites and are separated by 9.06 Å. (1)H-NMR and ES-MS data establish that the triple helical structure is maintained in solution. Spectrophotometric titrations (Ln = La, Eu) indicate log beta(23) = 24-25 and the formation of a 2:2 complex [Ln(2)(L(5))(2)](6+) (log beta(22) = 19-20). Quantum yield determination in acetonitrile shows that the terminal N,N-diethylcarboxamide groups in L(5) favor efficient intramolecular L(5) --> Eu(III) energy transfers leading to strong Eu-centered red luminescence, 50 times as intense as the luminescence observed when the carboxamide groups are replaced by substituted benzimidazole units in [Eu(2)(L(4))(3)](6+). Resistance toward hydrolysis also results from the use of carboxamide groups, and no quenching of luminescence is observed for [Eu(2)(L(5))(3)](6+) in moist acetonitrile up to 2.5 M water. The crucial role played by carboxamide groups for the control of structural, electronic, and photophysical properties is discussed. Replacing perchlorates by triflates allows the isolation of the dinuclear double-stranded helicate [Eu(2)(L(6))(2)(CF(3)SO(3))(4)(H(2)O(2))(2)](CF(3)SO(3))(2)(MeOH)(2)(H(2)O)(5)(.5), whose crystal structure (13a, C(85)H(106)Eu(2)F(18)N(16)O(30)S(6), monoclinic, C2/m, Z = 2) reveals a side-by-side arrangement of the two strands and 9-coordinate Eu ions linked through hydrogen-bonded water molecules.

Construction of two- and three-dimensional supramolecular networks with an encapsulated lanthanide(III) complex as building block and hydrogen-bonded 4,4′-bipyridyl as spacer

Reaction of the tripodal ligand tris(2-benzimidazolylmethyl)amine (ntb) with hydrated lanthanide(III) perchlorates in methanol affords the complexes [Ln(ntb)2]3+ (Ln = Pr, Eu and Tb) in which the central Ln3+ ion is well encapsulated in a cubic coordination environment; in situ co-crystallization of the complexes in the presence of 4,4′-bipyridyl produces either a double salt containing the bipyridinium(1+) cation or adducts with two to three bipyridyl molecules, the latter adducts forming doubly interpenetrating two- or three-dimensional cationic networks.

Complexes of Yttrium and Lanthanide Perchlorates with 4-N-(5′-Nitro-2′-Thienylidene)aminoantipyrine

Yttrium and lanthanide perchlorate complexes with the Schiff base 4-N-(5′-nitro-2′-thienylidene)aminoantipyrine (NTAAP) of the composition [Ln(NTAAP)2(CIO4)2]CIO4 (where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er) have been synthesized and characterized by elemental analyses, electrical conductance in non-aqueous solvents, magnetic susceptibility measurements, infrared, electronic, proton NMR spectra and thermogravimetric analyses. The Schiff base NTAAP acts as a neutral tridentate ligand in these complexes coordinating through the carbonyl oxygen, azomethine nitrogen and sulphur of the thiophene ring. Two of the perchlorate ions are coordinated monodentately, the third one is ionic. The complexes are thermally stable up to 110°C and undergo decomposition in two stages. A coordination number of eight may be assigned to the metal in these complexes. Referee I: J. G. Watkin Referee II: R. D. Archer

Complexes of Yttrium and Lanthanide Perchlorates with 4-N-(2′-Furfurylidene)aminoantipyrine

Yttrium and lanthanide perchlorate complexes with 4-N-(2′-furfurylidene)aminoantipyrine (FAA) of the composition [Ln(FAA)3(CIO4)2]ClO4 (where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Er) have been synthesised and characterized by elemental analyses, molar conductance in non-aqueous solvents, magnetic susceptibility measurements, infrared, electronic as well as proton NMR spectra and thermogravimetric analyses. In these complexes the ligand FAA acts as a neutral tridentate one coordinating through the carbonyl oxygen, azomethine nitrogen and oxygen of the furan ring. Two of the perchlorate ions are coordinated monodentately and the third one being ionic. Referee I: G. R. Choppin Referee II: K. P. Gable

Thermal decomposition kinetics and mechanism of lanthanide perchlorate complexes of 4- N-(4′-antipyrylmethylidene)aminoantipyrine

The thermal decomposition behaviour of lanthanide perchlorate complexes of the Schiff base, 4- N-(4′-antipyrylmethylidene)aminoantipyrine (AA), have been studied using TG and DTG analyses. The phenomenological and kinetic aspects of the TG curves are investigated for the evaluation of kinetic parameters such as activation energy, pre-exponential factor and entropy of activation using the Coats-Redfern equation. The rate controlling process obeys the ‘Mampel model’, representing random nucleation with one nucleus on each particle. There is no regular variation in the values of kinetic parameters for the decomposition of these complexes. The kinetic parameters indicate that the ligand is loosely bound to the metal ion and the activated complex is more ordered than the reactants.

FT-IR and fluorometric investigation of rare-earth and metal ion solvation Part 16. Solid state and solution study of acetonitrile-coordinated lanthanid solvates [Ln(CH 3CN) 9](AlCl 4) 31

The CH 3CN coordinated lanthanide solvates [Ln(CX 3CN) 9(AlCl 4) 3 have been studied by means of luminescence (XH,D; LnEu, Tb) and FT-IR spectroscopy (XH; LnLa, Nd, Gd, Er, Lu). High resolution luminescence spectra, recorded at 77 K, of the [Eu(CH 3CN) 9(AlCl 4) 3 microcrystalline compound, show the Eu III ion located in one unique coordination site with a local symmetry close to D 3 h . The same local structure is preserved in Eu-doped La and Dg solvates, pointing to an isostructural series of compounds. The lifetime of the Eu( 5D 0) level amounts to 5.07 ms in the deuterated solvate. The tricapped trigonal prismatic geometry is lost in 0.01 M solutions in anhydrous acetonitrile and propylene carbonate. Analysis of the 3D 0«r 7F 0 transition points to the presence of at least two different species in equilibrium. Vibrational spectra evidence a sizable Ln-acetonitrile interaction substantiated by the shifts of the v 2 and v 3+ v 4 vibrations which increase lienarly with the increase in electronic density of the lanthanide ions and which are identical to those observed for lanthanide perchlorate and nitrate solutions under the same experimental conditions. This means that the Ln-acetonitrile interaction is mainly governed by electrostatic factors. In mixed propylene carbonate-acetonitrile solutions of [La(CH 3CN) 9](AlCl 4) 3 complexes, lanthanum ions are preferentially solvated by propylene carbonate molecules for R=[CH 3CN] t /[Ln III ] t ,⩽50. For R=100, four acetonitrile molecules are bonded to the lanthanum ion.

Complexes of yttrium and lanthanide perchlorate with 4-N-(2′-thienylidene)aminoantipyrine

Complexes of yttrium and lanthanide perchlorate with 4-N-(2′-thienylidene)aminoantipyrine

Complexes of Rare Earth Perchlorates with 4-N-(4′-Antipyrylmethylidene)aminoantipyrine

Abstract Rare earth perchlorate complexes with the Schiff base 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) of the types [Ln(AA)2ClO4](ClO4)2 (where Ln = La, Pr, Nd, Sm and Eu) and [Ln(AA)3](ClO4)3 (where Ln = Gd, Dy, Ho, Er and Y) have been synthesised and characterised. In these complexes AA acts as a terdentate ligand. One of the perchlorate groups is coordinated monodentately only in the complexes of the light rare earths, whereas in the heavy rare earths perchlorate groups remain uncoordinated. The magnetic moments of these complexes agree well with the van Vleck values, suggesting non-participation of f-electrons in bonding.

ChemInform Abstract: Rare Earth Perchlorate Catalyzed Glycosidation of Glycosyl Fluorides with Trimethylsilyl Ethers.

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