Central Lanthanide Ion Research Articles

Synthesis, Structure, and Magnetic Properties of a New Family of Tetra-nuclear {Mn2IIILn2}(Ln = Dy, Gd, Tb, Ho) Clusters With an Arch-Type Topology: Single-Molecule Magnetism Behavior in the Dysprosium and Terbium Analogues

Sequential reaction of Mn(II) and lanthanide(III) salts with a new multidentate ligand, 2,2'-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (LH3), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn2Dy2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (1), [Mn2Gd2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (2), [Mn2Tb2(LH)4(μ-OAc)2](NO3)2·2H2O·2CH3OH·Et2O (3), and [Mn2Ho2(LH)4(μ-OAc)2]Cl2·5CH3OH (4). All of these dicationic complexes possess an arch-like structural topology containing a central Mn(III)-Ln-Ln-Mn(III) core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn(III) ions. Four doubly deprotonated LH(2-) chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln(3+) ions in 1-4 causes pronounced zero-field splitting for Tb(3+), Dy(3+), and Ho(3+). For 1 and 3, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (1) and 13 K (3) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of ΔE = 16.8 cm(-1) (1) and 33.8 cm(-1) (3).

Propeller-like heterotrinuclear CuII–LnIII–CuII compounds – Physicochemical properties

The new heterotrinuclear compounds [Cu2Ln(L)2(NO3)(H2O)2](NO3)2·3H2O (where Ln=Sm (1), Eu (2) and L=C19H18N2O4Br2 is the deprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine,) have been synthesized and characterized by FTIR, TG-FTIR, TG/DSC and single crystal X-ray analyses. The complexes of 1 and 2 are isostructural. In the trinuclear compounds two terminal copper(II) ions are coordinated by imino and phenolate oxygen atoms, whereas the central lanthanide(III) ion is bound to the phenolate and methoxy oxygen atoms of the Schiff base ligands. The first change in mass estimated from TG curve corresponds to the loss of water molecules. The decomposition of the Schiff base ligand starts above 200°C. The final decomposition solid products are CuO and Ln2CuO4. The TG-FTIR results show that the main gaseous products in whole decomposition process of complexes are water (H2O), carbon dioxide (CO2), carbon monoxide (CO), nitric oxides (NOx) and bromomethane (CH3Br).

NMR chemical shift as analytical derivative of the Helmholtz free energy

We present a theory for the temperature-dependent nuclear magnetic shielding tensor of molecules with arbitrary electronic structure. The theory is a generalization of Ramsey's theory for closed-shell molecules. The shielding tensor is defined as a second derivative of the Helmholtz free energy of the electron system in equilibrium with the applied magnetic field and the nuclear magnetic moments. This derivative is analytically evaluated and expressed as a sum over states formula. Special consideration is given to a system with an isolated degenerate ground state for which the size of the degeneracy and the composition of the wave functions are arbitrary. In this case, the paramagnetic part of the shielding tensor is expressed in terms of the g and A tensors of the electron paramagnetic resonance spin Hamiltonian of the degenerate state. As an illustration of the proposed theory, we provide an explicit formula for the paramagnetic shift of the central lanthanide ion in endofullerenes Ln@C(60), with Ln = Ce(3+), Nd(3+), Sm(3+), Dy(3+), Er(3+), and Yb(3+), where the ground state can be a strongly spin-orbit coupled icosahedral sextet for which the paramagnetic shift cannot be described by previous theories.

Family of dumbbell Ni4Ln2 (Ln = Pr, Sm, Eu, Gd, Tb, Ho, Er) complexes: syntheses, structures, luminescent and magnetic properties

The synthesis and characterization of a family of heterometallic Ni4Ln2 complexes (Ln = Pr(1), Sm(2), Eu(3), Gd(4), Tb(5), Ho(6) and Er(7)) of the formula [Ni2LnL1L2(OH)(H2O)]2 are reported, where H4L1 is 3,3′-(1E,1′E)-(2,2′-(2-aminoethylazanediyl)bis(ethane-2,1-diyl)bis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-hydroxybenzoic acid) and H2L2 is 3-formyl-2-hydroxybenzoic acid. The molecular structures of 1–7 were determined by single-crystal X-ray diffraction and reveal that they are isostructural. In all of these compounds, the six metal ions are held together to form a novel Ni4Ln2O10 core and exhibit a relatively rare dumbbell-type structure. In these compounds, the Ni ions are in slightly distorted square-pyramidal or octahedral environments. An all-oxygen coordination environment (8O) is present around the central lanthanide ion, which is present in a distorted square antiprismatic geometry. The Ln–Ln and Ln–Oavg bond distances in 1–7 show a gradual reduction proceeding from 1 to 7, in accordance with the lanthanide contraction. The luminescent properties of all the compounds have been studied. The magnetic susceptibility analysis demonstrate antiferromagnetic interactions within complex 4.

Advantages of paramagnetic chemical exchange saturation transfer (CEST) complexes having slow to intermediate water exchange properties as responsive MRI agents

Paramagnetic chemical exchange saturation transfer (PARACEST) complexes are exogenous contrast agents that have great potential to further extend the functional and molecular imaging capabilities of magnetic resonance. As a result of the presence of a central paramagnetic lanthanide ion (Ln(3+) ≠ La(3+) , Gd(3+) , Lu(3+) ) within the chelate, the resonance frequencies of exchangeable protons bound to the PARACEST agent are shifted far away from the bulk water frequency. This large chemical shift, combined with an extreme sensitivity to the chemical exchange rate, make PARACEST agents ideally suited for the reporting of significant biological metrics, such as temperature, pH and the presence of metabolites. In addition, the ability to turn PARACEST agents 'off' and 'on' using a frequency-selective saturation pulse gives them a distinct advantage over Gd(3+) -based contrast agents. A current challenge for PARACEST research is the translation of the promising in vitro results into in vivo systems. This short review article first describes the basic theory behind PARACEST contrast agents, their benefits over other contrast agents and their applications to MRI. It then describes some of the recent PARACEST research results: specifically, pH measurements using water molecule exchange rate modulation, T2 exchange contrast caused by water molecule exchange, the use of ultrashort TEs (TE < 10 µs) to overcome T2 exchange line broadening and the potential application of T2 exchange as a new contrast mechanism for MRI.

2-Aminoisobutyric Acid in Co(II) and Co(II)/Ln(III) Chemistry: Homometallic and Heterometallic Clusters

The synthesis and magnetic properties of 13 new homo- and heterometallic Co(II) complexes containing the artificial amino acid 2-amino-isobutyric acid, aibH, are reported: [Co(II)(4)(aib)(3)(aibH)(3)(NO(3))](NO(3))(4)·2.8CH(3)OH·0.2H(2)O (1·2.8CH(3)OH·0.2H(2)O), {Na(2)[Co(II)(2)(aib)(2)(N(3))(4)(CH(3)OH)(4)]}(n) (2), [Co(II)(6)La(III)(aib)(6)(OH)(3)(NO(3))(2)(H(2)O)(4)(CH(3)CN)(2)]·0.5[La(NO(3))(6)]·0.75(ClO(4))·1.75(NO(3))·3.2CH(3)CN·5.9H(2)O (3·3.2CH(3)CN·5.9H(2)O), [Co(II)(6)Pr(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Pr(NO(3))(5)]·0.41[Pr(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.59[Co(NO(3))(3)(H(2)O)]·0.2(ClO(4))·0.25H(2)O (4·0.25H(2)O), [Co(II)(6)Nd(III)(aib)(6)(OH)(3)(NO(3))(2.8)(CH(3)OH)(4.7)(H(2)O)(1.5)]·2.7(ClO(4))·0.5(NO(3))·2.26CH(3)OH·0.24H(2)O (5·2.26CH(3)OH·0.24H(2)O), [Co(II)(6)Sm(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Sm(NO(3))(5)]·0.44[Sm(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.56[Co(NO(3))(3)(H(2)O)]·0.22(ClO(4))·0.3H(2)O (6·0.3H(2)O), [Co(II)(6)Eu(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)OH)(4.87)(H(2)O)(1.13)](ClO(4))(2.5)(NO(3))(0.5)·2.43CH(3)OH·0.92H(2)O (7·2.43CH(3)OH·0.92H(2)O), [Co(II)(6)Gd(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.9)(H(2)O)(1.2)]·2.6(ClO(4))·0.5(NO(3))·2.58CH(3)OH·0.47H(2)O (8·2.58CH(3)OH·0.47H(2)O), [Co(II)(6)Tb(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Tb(NO(3))(5)]·0.034[Tb(NO(3))(3)(ClO(4))(0.5)(H(2)O)(0.5)]·0.656[Co(NO(3))(3)(H(2)O)]·0.343(ClO(4))·0.3H(2)O (9·0.3H(2)O), [Co(II)(6)Dy(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.92)(H(2)O)(1.18)](ClO(4))(2.6)(NO(3))(0.5)·2.5CH(3)OH·0.5H(2)O (10·2.5CH(3)OH·0.5H(2)O), [Co(II)(6)Ho(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·0.27[Ho(NO(3))(3)(ClO(4))(0.35)(H(2)O)(0.15)]·0.656[Co(NO(3))(3)(H(2)O)]·0.171(ClO(4)) (11), [Co(II)(6)Er(III)(aib)(6)(OH)(4)(NO(3))(2)(CH(3)CN)(2.5)(H(2)O)(3.5)](ClO(4))(3)·CH(3)CN·0.75H(2)O (12·CH(3)CN·0.75H(2)O), and [Co(II)(6)Tm(III)(aib)(6)(OH)(3)(NO(3))(3)(H(2)O)(6)]·1.48(ClO(4))·1.52(NO(3))·3H(2)O (13·3H(2)O). Complex 1 describes a distorted tetrahedral metallic cluster, while complex 2 can be considered to be a 2-D coordination polymer. Complexes 3-13 can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co(II)(6)] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2-300 K range for complexes 1, 3, 5, 7, 8, 10, 12, and 13, revealing the possibility of single molecule magnetism behavior for complex 10.

Synthesis, characterization of the luminescent lanthanide complexes with copolymer of (Z)‐4‐oxo‐4‐phenyloxyl‐2‐butenoic acid and styrene

AbstractThe copolymers of (Z)‐4‐oxo‐4‐phenoxyl‐2‐butenoic acid with styrene (PSt/OPBA) and their macromolecular luminous lanthanide complexes (Ln‐PSt/OPBA) have been synthesized and characterized by means of GPC, elemental analysis, FTIR, X‐ray powder diffraction, spectral analysis, and thermal analysis. The IR studies showed that the carboxylic groups on the side chain of the polymer were coordinated to lanthanide ions by bidentate manner. However, the ethereal oxygen, instead of carbonyl, also bonded to the central lanthanide ions, which was an intriguing phenomenon for ester‐coordinated complexes. X‐ray diffraction experiments revealed that these PSt/OPBA copolymers were amorphous, but Ln‐PSt/OPBA were crystalline, in which the complex Eu‐Lc belonged to a high symmetric structure of orthorhombic quadratic system, with a = 10.59 ± 0.02 Å, c = 8.02 ± 0.01 Å; c/a = 0.763. In addition, the value δ (the number of free carboxylic groups) in Ln‐PSt/OPBA complexes increased with the decreasing mole ratio of styrene in the copolymers, while it decreased with increasing pH values of the solution. Eu3+ and Tb3+ complexes exhibited characteristic fluorescence with comparatively high brightness and good monochromaticity, and the fluorescence intensity was enhanced with increasing the content of lanthanide up to around 18 wt % without typical fluorescence concentration quenching behavior in the solid state. So using polymers as a matrix, Ln‐PSt/OPBA are likely to provide new materials that possess specific properties and desired features. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Establishing the Binding Affinity of Organic Carboxylates to 15-Metallacrown-5 Complexes

The reaction of L-phenylalanine hydroxamic acid (H(2)L-pheHA) with copper(II) and lanthanide(III) salts yields 15-Metallacrown-5 structures of the general composition Ln(X)n[Cu(II)(L-pheHA)](5)((3-n)+) where X can represent a wide variety of anions. With five copper ions and one central lanthanide ion, the Ln[15-MC-5] complexes have multiple positions where these anionic guests may bind to the metallacrown host. In addition, these metallacrowns are amphiphilic, containing one face that is primarily hydrophobic (due to the five benzyl side chains which are oriented upon the same face of the molecule) and a face that is hydrophilic which has no impediment to solvent access. While it has been known that aromatic carboxylates bind preferentially to the hydrophobic face and short chain aliphatic carboxylates bind preferentially to the hydrophilic face, there have been no quantitative assessments of the stability of these host-guest complexes. Using Isothermal Calorimetry (ITC) we have determined the binding constants for several carboxylate anions to a variety of metallacrown complexes. The affinities of anions that coordinate to the lanthanide ion on the hydrophobic face are related to the hydrophobicities of the guests, with higher binding strength observed for the more hydrophobic carboxylates. Central metal such as La(III) or Nd(III) which are nine coordinate are able to accommodate two guests on the hydrophobic side; however, central metals such as Gd(III) or Dy(III) which are eight coordinate are limited to encapsulating one guest into the hydrophobic pocket. A second guest, bound to the hydrophilic face is often observed with these 8-coordinate lanthanides. The significantly weaker second binding constant between benzoate and Gd(III)[15-MC-5] supports the model that the second benzoate binds to the central metal through the hydrophilic side. Unlike the Gd(III)[15-MC-5], the higher binding constant of the second benzoate with La(III)[15-MC-5] is consistent with the crystallographic model which shows that the second guest binds to the hydrophobic side.

2-Mercaptobenzothiazolate complexes of rare earth metals and their electroluminescent properties

We have demonstrated the electroluminescent (EL) properties of 2-mercaptobenzothiazolate complexes of rare earth metals [Ln(mbt) 3, Ln = Y, Sm, Eu, Gd, Tb, Dy, Tm] using simple non-doped two-layer organic light emitting diode with the configuration of indium tin oxide/ N, N′-bis(3-methylphenyl)- N, N′-diphenylbenzidine/Ln(mbt) 3/Yb. It was found that 2-mercaptobenzothiazolate complexes have highly efficient intra-energy transfer from the singlet to the triplet state of the ligand, and then to the excited state of the central lanthanide ions. Thus Y(mbt) 3 and Gd(mbt) 3 exhibit the broad ligand-centered emission with maximum near 600 nm and Dy(mbt) 3, Tb(mbt) 3 and Tm(mbt) 3 complexes exhibit pure sharp emission bands from the intra f–f transitions of lanthanide ions Tb 3+: 5D 4 → 7F 6 (492 nm), 5D 4 → 7F 5 (547 nm), 5D 4 → 7F 4 (589 nm), 5D 4 → 7F 3 (624 nm); Dy 3+: 4F 9/2 → 6H 13/2 (575 nm) and Tm 3+: 3H 4– 3H 6 (795 нм).

Synthesis, Structure, and Magnetism of Heterobimetallic Trinuclear Complexes {[L2Co2Ln][X]} [Ln = Eu, X = Cl; Ln = Tb, Dy, Ho, X = NO3; LH3 = (S)P[N(Me)N═CH−C6H3-2-OH-3-OMe]3]: A 3d−4f Family of Single-Molecule Magnets

Sequential reaction of LH3 (LH3 = (S)P[N(Me)N=CH-C6H3-2-OH-3-OMe]3) with Co(OAc)2 x 4 H2O followed by reaction with lanthanide salts afforded trinuclear heterobimetalllic compounds {[L2Co2Ln][X]} [Ln = Eu (1), X = Cl; Ln = Tb (2), Dy (3), Ho (4), X = NO3] in excellent yields. These compounds retain their integrity in solution as determined by electrospray ionization mass spectrometry studies. The molecular structures of 1-4 were confirmed by a single-crystal X-ray structural study and reveal that these are isostructural. In all of the compounds, the three metal ions are arranged in a perfectly linear manner and are held together by two trianionic ligands, L3-. The two terminal Co(II) ions contain a facial coordination environment (3N, 3O) comprising three imino nitrogen atoms and three phenolate oxygen atoms. The coordination geometry about the cobalt atom is severely distorted. An all-oxygen coordination environment (12O) is present around the central lanthanide ion, which is present in a distorted icosahedral geometry. The coordination sphere around the lanthanide ion is achieved by utilizing three phenolate oxygen atoms and three methoxy oxygen atoms of each ligand. In all of these trinuclear complexes (1-4), the Co-Ln distances are around 3.3 A, while the Co-Co distances range from 6.54 to 6.60 A. The screw-type coordination mode imposed by the ligand induces chirality in the molecular structure, although all of the complexes crystallize as racemates. Magnetic properties of 1-4 have been studied in detail using dc and ac susceptibility measurements. Dynamic measurements reveal that 2-4 display a single-molecule magnet behavior, while the Co2Eu (1) analogue does not show any out-of-phase ac susceptibility.

Searching for the Exchange Shift: a Set of Test Systems

We suggest that intramolecular exchange coupling J in solutions can possibly be measured with just a ruler using an analogue of the nuclear magnetic resonance paramagnetic shift. If one of the two coupled electron spins is rapidly relaxing, the resulting electron paramagnetic resonance (EPR) spectrum of the system is the resolved spectrum for the second spin with a shifted g-factor. The amount and the sense of the shift are both linear in J, which thus can be obtained from the measured shift by simple algebra. We prepared a set of complexes of rare-earth ions with nitroxides to probe this idea, but the sought effect was not yet found indicating J < 0.1 cm−1 for these systems. Either the radical centers should be brought closer to the central lanthanide ion, or the ion itself should be substituted for a rapidly relaxing transition-metal ion, e.g., Cr2+ or Co2+. Furthermore we report evolving EPR spectra that reflect the inner life of the complexes in solution.

Trinuclear Heterobimetallic Ni2Ln complexes [L2Ni2Ln][ClO4] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er; LH3= (S)P[N(Me)N═CH−C6H3-2-OH-3-OMe]3): From Simple Paramagnetic Complexes to Single-Molecule Magnet Behavior

The reaction of LH3 with Ni(ClO4)(2).6H 2O and lanthanide salts in a 2:2:1 ratio in the presence of triethylamine leads to the formation of the trinuclear complexes [L2Ni2Ln][ClO4] (Ln=La (2), Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8), Tb (9), Dy (10), Ho (11) and Er (12) and L: (S)P[N(Me)NCH-C6H3-2-O-3-OMe]3). The cationic portion of these complexes consists of three metal ions that are arranged in a linear manner. The two terminal nickel(II) ions are coordinated by imino and phenolate oxygen atoms (3N, 3O), whereas the central lanthanide ion is bound to the phenolate and methoxy oxygen atoms (12O). The Ni-Ni separations in these complexes range from 6.84 to 6.48 A. The Ni-Ni, Ni-Ln and Ln-O phenolate bond distances in 2-12 show a gradual reduction proceeding from 2 to 12 in accordance with lanthanide contraction. Whereas all of the compounds (2-12) are paramagnetic systems, 8 displays a remarkable ST=(11)/2 ground state induced by an intramolecular Ni. . .Gd ferromagnetic interaction, and 10 is a new mixed metal 3d/4f single-molecule magnet generated by the high-spin ground state of the complex and the magnetic anisotropy brought by the dysprosium(III) metal ion.

Increasing the luminescence of lanthanide complexes

This review compares the chemical and physical properties of lanthanide ion complexes and of other narrow-emitting species that can be used as labels for cytometry. A series of luminescent lanthanide ion macrocyclic complexes, Quantum Dyes, which do not release or exchange their central lanthanide ion, do accept energy transfer from ligands, and are capable of covalent binding to macromolecules, including proteins and nucleic acids, is described and their properties are discussed. Two methods are described for increasing the luminescence intensity of lanthanide ion complexes, which intrinsically is not as high as that of standard fluorophores or quantum dots. One method consists of adding a complex of a second lanthanide ion in a micellar solution (columinescence); the other method produces dry preparations by evaporation of a homogeneous solution containing an added complex of a second lanthanide ion or an excess of an unbound antenna ligand. Both methods involve the Resonance Energy Transfer Enhanced Luminescence, RETEL, effect as the mechanism for the luminescence enhancement.

Energy transfer study of europium–tetracycline complexes

The aim of this work was to study the energy transfer mechanisms from the ligand to the central lanthanide ion of tetracycline–europium (Tc–Eu) complex. The absorption spectra of a EuCl 3.H 2O solution was measured and absorption cross-section of Eu 3+ was estimated. The observed overlap predicts a resonant energy transfer from Tetracycline to Eu 3+. The microscopic parameter of energy transfer was obtained using the overlap integral calculation considering a dipole–dipole energy transfer mechanism and results were compared considering an energy transfer by exchange. In this work, we report also the optical properties of Tc–Eu complex when urea hydrogen peroxide is added to the aqueous solution.

Synthesis, crystal structures and theoretical study of mixed ligand complexes of lanthanides acetylacetonates with o-phenanthroline and 2,2′-dipyridyl: The unexpected inverted electrostatic trend in stability

Synthesis of mixed ligand complexes [Lu(acac) 3phen] 1 and [Lu(acac) 3dipy] 2 was carried out. Complexes 1 and 2 have mononuclear structures with six oxygen atoms and two nitrogen atoms in the coordination sphere of the central Lu 3+ ion. Theoretical calculations of structures and properties of mixed ligand complexes [Ln(acac) 3Q] (where Ln=La, Gd, Lu; Q=phen, dipy) were performed at the DFT/B3PW91 level. The natural bond orbital analysis (NBO) was used to characterize the electronic structures of complexes. The features of crystal structures of complexes [Ln(acac) 3Q] in lanthanide row were explained taking into account the bond nature. The influence of both nature of central lanthanide ion and neutral additional ligand on structures and properties of complexes under investigation is discussed. The Ln(acac) 3—Q bond energy was found to be decreased from La-based complexes to Lu-based compounds. Thus, the unexpected inverted electrostatic trend, i.e. a decrease in stability along the lanthanide series, has been found out.

Structure and magnetic properties of 3d–4f heterometallic complexes containing di-2-pyridyl ketoximate: An approach to single-molecule magnets

Abstract [{Ln(hfac)3}2{Ni(dpk)2(phen)}] (1Ln) and [{Ln(hfac)3}2{Ni(dpk)2(py)2}] (2Ln) were synthesized and characterized, where dpk = di-2-pyridyl ketoxmate and Ln = La, Tb, Dy, Ho, Er. The N–O groups from dpk bridged the central nickel(II) ion and terminal lanthanide(III) ions, giving a linear trinuclear array. Dc magnetic susceptibility measurements revealed that they did not possess appreciable intramolecular ferromagnetic or ferrimagnetic interaction. Ac magnetic susceptibility measurements clarified that frequency dependence of out-of-phase ac susceptibility was observed only for Dy derivatives 1Dy and 2Dy, which is regarded as an indication of single-molecule magnets.

Self-assembly of lanthanide mixed-carboxylates coordination polymers

Two new mixed-ligands lanthanide coordination polymers, [Ln(Ac)(ip)(H 2O) 2]·0.5H 2O (Ln=La ( 1); Ln=Eu ( 2); Ac=acetate; ip=isophthalate) have been synthesized under hydrothermal condition. Single-crystal X-ray analyses show that complexes 1 and 2 are three-dimensional structure in which lanthanide ions are bridged by monocarboxylate ligand, acetate or dicarboxylate ligand, isophthalate. And the central lanthanide ions, La 3+ and Eu 3+, are both nine-coordinate with oxygen atoms. The thermogravimetric analysis was carried out to examine the thermal stability of the title complexes. And the photoluminescence property of complex 2 was also investigated.

Spectral Study of the Co‐luminescence Effect of Lanthanide Ternary Complexes with Benzoic Acid and Phenanthroline

The photoacoustic (PAS) spectra and luminescence spectra of Eu(Hba)3 Phen and coprecipitates Eu0.6Ln0.4(Hba)3 Phen complexes (Ln3+:Y3+, Nd3+; Hba: benzoic acid; Phen: phenanthroline) have been measured, and the co‐luminescence effect of the coprecipitates are reported. The PAS intensities of the central lanthanide ions are interpreted in terms of the probability of nonradiative transitions. It is found that the PAS intensity of the ligand bears a relationship with the energy transfer processes. The PAS intensity in the region of ligand absorption increases in the order of Eu0.6Nd0.4(Hba)3 Phen > Eu(Hba)3 Phen > Eu0.6Y0.4(Hba)3 Phen, which indicates that addition of the second lanthanide ions in each case changes the relaxation processes of the complexes. The energy transfer and relaxation processes are discussed in combination with the luminescence spectra.

Synthesis and characterization of ethylthioethylcyclopentadienyl organolanthanide complexes: CpLnCl (Ln=Gd, Dy), Cp2LnCpTh (Ln=Yb, Sm, Dy, Y) and CpThErCl2·2THF

AbstractSix new ethylthioethylcyclopentadienyl containing organolanthanide complexes CpLnCl [Ln=Gd (1), Dy (2)] and Cp2LnCpTh [Cp=C5H5, Ln=Yb (3), Sm (4), Dy (5), Y (6)] were synthesized by the reaction of ethylthioethyl‐cyclopentadienyl (CpTh) sodium salt with LnCl3 or Cp2LnCl in THF. Complexes 1–6 were characterized by elemental analyses, infrared and mass spectroscopies. The molecular structures of complexes 1–3 were also determined by the X‐ray single crystal diffraction. The results show that the side‐chain sulfur atom on the ethylthioethylcyclopentadienyl ring can form intramolecular chelating coordination to the central lanthanide ion, improving the stability of organolanthanide complexes and reducing the number of coordinated THF molecules.

Study of lanthanide complexes with salicylic acid by photoacoustic and fluorescence spectroscopy

Solid complexes Ln(Sal) 3·H 2O (Sal: salicylic acid; Ln: La 3+, Nd 3+, Eu 3+, Tb 3+) are synthesized, and their photoacoustic (PA) spectra in the UV-Vis region have been recorded. PA intensities of central lanthanide ions are interpreted in terms of the probability of nonradiative transitions. It is found that PA intensity of the ligand increases in the order of Tb(Sal) 3·H 2O < La(Sal) 3·H 2O < Eu(Sal) 3·H 2O < Nd(Sal) 3·H 2O. Different PA intensities of the ligand are interpreted by comparison with the fluorescence spectra. Ternary complexes Eu(Sal) 3Phen and Tb(Sal) 3Phen (Phen: 1,10-phenanthroline) are synthesized. Compared with their binary complexes, PA intensity of the ligand Sal decreases for Eu(Sal) 3Phen, while the reverse is true for that of Tb(Sal) 3Phen. The luminescence of Eu 3+ increases remarkably when Phen is introduced, and luminescence of Tb 3+ decreases greatly when Phen is added. The intramolecular energy transfer and relaxation processes in the complexes are discussed from two aspects: radiative and nonradiative relaxations.