Neodymium Complexes Research Articles

Synthesis and cytotoxic activities of group 3 metal complexes having monoanionic tridentate ligands

Complexes of scandium, yttrium, samarium and neodymium bearing monoanionic tridentate ancillary ligands have been synthesized and characterized. The cytotoxic activities of novel compounds, as well as that of similar compounds previously reported have been evaluated on rat glioma (C6), murine fibrosarcoma (WHEI-164) and human embryonic kidney (HEK-293) cell lines. Scandium complex with quinolinephenoxyamine (NNHO) ligand showed very interesting activity against C6 cell line.

ChemInform Abstract: Synthesis, Physicochemical Characterization and Cytotoxic Screening of New Complexes of Cerium, Lanthanum and Neodymium with Niffcoumar Sodium Salt.

Abstract The complexes of the types Ln(HN)3.nH2O [where Ln = Ce, La, Nd; HN = Niffcoumar] have been synthesized by reaction of Niffcoumar sodium salt and the appropriate lanthanide nitrates. The solid complexes have been characterized and identified on the basis of elemental analysis, conductivities, IR- and 1H-NMR-spectroscopy. We suppose that the lacton- and keto-carbonyl oxygen atoms of Niffcoumar are bonded to the metal ion probably as a bidentate ligand. The experimental data obtained by MTT-assay show that all tested compounds manifest a similar low cytotoxic activity on lymphoma derived P3HR1 cells (20% maximum cell growth inhibition). The complexes of La and Nd have been shown to be more cytotoxic than the Ce complex against K-562 cells (about 75% maximal growth inhibition). Low to moderate cytotoxic activity has been established for the complexes of La and Ce on TPH-1 cells (25% maximum inhibition of cell growth). Our data indicate that the lanthanide complexes may have some antitumour potential which depends on the metal and the cell line used.

Solution studies of lanthanide (III) complexes based on 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and 1,10-phenanthroline Part-I: Synthesis, 1H NMR, 4 f–4 f absorption and photoluminescence

Solution studies on the complexes of the type [Ln(hfaa) 3(phen) 2] (Ln = La, Pr and Nd) and [Ln(hfaa) 3phen] (Ln = Nd, Ho, Er and Yb; hfaa stands for the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and phen stands for 1,10-phenanthroline) are presented. These complexes are synthesized in high yields by an in situ method in which hfaa, ammonium hydroxide, lanthanide chlorides and phen were allowed to react in 3:3:1:1 molar ratio in ethanol. In the case of neodymium both eight- and ten-coordinate complexes are isolated. The paramagnetic shifts of the methine protons of β-diketone have their sign opposed to those of paramagnetic shifts of phen protons and the shifts are dominated by dipolar interactions. The inter- and intramolecular shift ratios have been calculated and discussed. The 4 f–4 f absorption spectra of the complexes of Pr, Nd, Ho and Er are analyzed. The eight- and ten-coordinate neodymium complexes display distinctively different band shapes of the 4G 5/2, 2G 7/2 ← 4I 9/2 hypersensitive transition. The efficient energy transfer from ligand to Pr(III) is reflected by strong red luminescence of this complex at room temperature.

Borane and Borohydride Complexes of the Rare-Earth Elements: Synthesis, Structures, and Butadiene Polymerization Catalysis

The reaction of potassium 2,5-bis[N-(2,6-diisopropylphenyl)iminomethyl]pyrrolyl [(dip(2)-pyr)K] with the borohydrides of the larger rare-earth metals, [Ln(BH(4))(3)(thf)(3)] (Ln=La, Nd), afforded the expected products [Ln(BH(4))(2)(dip(2)-pyr)(thf)(2)]. As usual, the trisborohydrides reacted like pseudohalide compounds forming KBH(4) as a by-product. To compare the reactivity with the analogous halides, the dimeric neodymium complex [NdCl(2)(dip(2)-pyr)(thf)](2) was prepared by reaction of [(dip(2)-pyr)K] with anhydrous NdCl(3). Reaction of [(dip(2)-pyr)K] with the borohydrides of the smaller rare-earth metals, [Sc(BH(4))(3)(thf)(2)] and [Lu(BH(4))(3)(thf)(3)], resulted in a redox reaction of the BH(4) (-) group with one of the Schiff base functions of the ligand. In the resulting products, [Ln(BH(4)){(dip)(dip-BH(3))-pyr}(thf)(2)] (Ln=Sc, Lu), a dinegatively charged ligand with a new amido function, a Schiff base, and the pyrrolyl function is bound to the metal atom. The by-product of the reaction of the BH(4) (-) anion with the Schiff base function (a BH(3) molecule) is trapped in a unique reaction mode in the coordination sphere of the metal complex. The BH(3) molecule coordinates in an eta(2) fashion to the metal atom. The rare-earth-metal atoms are surrounded by the eta(2)-coordinated BH(3) molecule, the eta(3)-coordinated BH(4) (-) anion, two THF molecules, and the nitrogen atoms from the Schiff base and the pyrrolyl function. All new compounds were characterized by single-crystal X-ray diffraction. Low-temperature X-ray diffraction data at 6 K were collected to locate the hydrogen atoms of [Lu(BH(4)){(dip)(dip-BH(3))-pyr}(thf)(2)]. The (DIP(2)-pyr)(-) borohydride and chloride complexes of neodymium, [Nd(BH(4))(2)(dip(2)-pyr)(thf)(2)] and [NdCl(2)(dip(2)-pyr)(thf)](2), were also used as Ziegler-Natta catalysts for the polymerization of 1,3-butadiene to yield poly(cis-1,4-butadiene). Very high activities and good cis selectivities were observed by using each of these complexes as a catalyst in the presence of various cocatalyst mixtures.

Toward understanding the thermodynamics of TALSPEAK process. Medium effects on actinide complexation

The ingenious combination of lactate and diethylenetriamine-N,N,N',N",N"-pentaacetic acid (DTPA) as an aqueous actinide-complexing medium forms the basis of the successful separation of americium and curium from lanthanides known as the TALSPEAK process. While numerous reports in the prior literature have focused on the optimization of this solvent extraction system, considerably less attention has been devoted to the understanding of the basic thermodynamic features of the complex fluids responsible for the separation. The available thermochemical information for both lactate and DTPA protonation and metal complexation reactions are representative of the behavior of these ions under idealized conditions. Significant departures from the speciation predicted based on reported thermodynamic values may be present in the TALSPEAK aqueous environment. Thus, thermodynamic parameters describing the separation chemistry of this process require further examination at conditions significantly removed from conventional ideal systems commonly employed in fundamental solution chemistry. In this report, calorimetric studies of lactate protonation equilibrium illustrate a distinct influence of nitrate, perchlorate, methylsulfonate and triflate on the thermodynamic parameters associated with TALSPEAK aqueous chemistry. Triflate is identified a closer non-complexing representative of lactate solution chemistry. The reported initial two stability constants for the complexation of americium and neodymium by lactate in triflate medium suggest that the identified medium effects do not significantly affect the speciation.

Mixed borohydride-chloride complexes of the rare earth elements

Abstract Mixed borohydride-chloride complexes of lanthanum and neodymium having the 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl ligand in the coordination sphere were synthesised by the reaction of potassium 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl [(DIP2-pyr)K] with a 1:1 mixture of [Ln(BH4)3(THF)3] and LnCl3 (Ln = La, Nd). Both compounds are dimeric in the solid state. The metal atoms are bridged almost symmetrically by two μ-chlorine atoms. Quantum chemical calculations for the lanthanum compound were performed to obtain a deeper insight into the bonding in the molecule.

Synthesis and characterization of lanthanum(III) and neodymium(III) complexes containing various Schiff bases

Some new complexes of lanthanum(III) and neodymium(III) with different Schiff bases (derived from salicylaldehyde with 2-methyl-1-aminobenzene and 2-aminopyridine have been synthesized and characterized by elemental (La/Nd, C, H, N and Cl) analysis, magnetic susceptibility measurements and spectral (UV-Visible, IR and FAB-MS) data. The Schiff bases, such as salicylidine-2-methyl-1-aminobenzene (smabH) and salicylidene-2-aminopyridine (sapH), bind in a bidentate fashion with the metals. A tentative structure for these complexes are proposed and suggested coordination number(s) six around neodymium(III) and eight around lanthanum(III) metal ions in the respective complexes of lanthanum(III) and neodymium(III) chloride.

Non-classical divalent lanthanide complexes

The synthesis of non-classical divalent lanthanide complexes, i.e. those not containing the classical samarium(II), europium(II) or ytterbium(II), was once thought impossible. Since 1997, when the first stable complex of thulium(II) was discovered, there has been many more examples of stable coordination and organometallic complexes of lanthanum(II), neodymium(II) and dysprosium(II) in addition to thulium(II), and the influence of the ligand system on the stability of the complexes is beginning to be understood. These non-classical divalent compounds show exceptional reactivity as some of them have been shown to activate dinitrogen at room temperature, together with related reduced divalent-like systems, and to undergo spontaneous intramolecular carbon-hydrogen bond activation. Many more examples of non-classical divalent compounds together with new aspects of their exciting reactivity should be discovered in the near future.

Fluorescence and DNA-binding spectral studies of neodymium(III) complex containing 2,2′-bipyridine, [Nd(bpy) 2Cl 3·OH 2

The interaction of [Nd(bpy) 2Cl 3·OH 2], where bipy is 2,2′-bipyridine, with DNA has been studied by absorption, emission, and viscosity measurements. [Nd(bpy) 2Cl 3·OH 2] showed absorption decreasing in charge transfer band with increasing of DNA. The binding constant, K b has been determined by absorption measurement and found to be (1.5 ± 0.1) × 10 5 M −1. The fluorescent of [Nd(bpy) 2Cl 3·OH 2] has been investigated in detail. The interaction was also studied by fluorescence quenching technique. The results of fluorescence titration revealed that DNA had the strong ability to quenching the intrinsic fluorescence of Nd(III) complex at 327 nm. The binding site number n, apparent binding constant K b and the Stern–Volmer quenching constant K SV have been determined. Thermodynamic parameters have been calculated according to relevant fluorescent data and Van’t Hoff equation. Characterization of bonding mode has been studied. The results suggested that the major interaction mode between [Nd(bpy) 2Cl 3·OH 2] and DNA was groove binding.

Synthesis and Solid‐State, Solution, and Luminescence Properties of Near‐Infrared‐Emitting Neodymium(3+) Complexes Formed with Ligands Derived from Salophen

AbstractA series of free ligands, H2L1, H2L2, H2L3, and H2L4, designed for the coordination and sensitization of near‐infrared(NIR)‐emitting Nd3+ were synthesized by modifying the salophen Schiff base with different numbers and locations of Br‐substituents. The nature of the Nd3+ complexes in solution was determined to be [ML2]− by spectrophotometric titrations as an indication that the different substituents do not affect significantly the nature of the formed species. The structures were determined in the solid phase from X‐ray diffraction experiments. The stoichiometries and structures in the solid state are different from those observed in solution. We established that the structures in the solid state can be partially controlled by the crystallization conditions. The ligands L1–L4 have the ability to sensitize Nd3+ through intramolecular energy transfer from the ligand to the metal ion. We quantified that the numbers and locations of Br‐substituents control the emitted luminescence intensity of the complex by the heavy‐atom effect.

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)]NHEt(3) (Ln = Nd, Eu, Tb for i = 1, 2; Ln = Eu for i = 3, 4) and of the monoaquo bypyridine-tetrazolate complex [Eu(H(2)O)(L7)(2)]NHEt(3) 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- (approximately 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.

Antibacterial Properties of a Kind of Schiff Base and Its Neodymium(III) and Zn(II) Complex (ZnNdL) on Escherichia coli

AbstractThe microcalorimetric and electronic microscopy methods were used to study the antibacterial activity of a Schiff base and its complex ZnNdL on Escherichia coli. The metabolic power‐time curves of the bacteria treated with the compounds were obtained, and the thermokinetic parameters were analyzed. The results show that the compounds (H2L, ZnNdL) have good activity on aerobic multiplying metabolism of E. coli, with the values of IC50 57.0 and 54.4 mg·L−1, respectively. In order to further investigate their mechanism on E. coli, transmission electronic microscopy and scanning electronic micrography were used to study the cell membrane change induced by the dibasic quadridentate Schiff base and its neodymium(III) complex. At a low concentration of the compound, the flagellum was inhibited and the cell did not show distinct changes. However, the flagella around the cell membrane were exfoliated, the morphology of E. coli was changed from a rod shape into a spherical shape or a short rod, and the flagella disappeared completely at a high concentration. The drug permeability into cell membrane was investigated by fluorescence quenching of probe dis‐C3‐(5), which suggested that H2L and ZnNdL could influence on the intra and extra cell membrane.

Imidophosphinate complexes of lanthanides. Investigation of thermochemical properties

New imidodiphosphinate complexes of neodymium and holmium of the general formula Ln[Ph2P(O)NP(O)Ph2]3 were synthesized. Results of investigation of their properties by means of differential scanning calorimetry, mass spectrometry, and the effusive Knudsen method are presented. Thermodynamic parameters of melting and sublimation are calculated.

Neodymium(III) triaquatrihydroxo(1,3-diamino-2-propanoltetraacetato)germanium(IV) hydrate [Ge(OH)(μ-HHpdta)(μ-OH)Nd(OH)(H2O)3] · H2O: Synthesis and crystal and molecular structure

The heteronuclear germanium(IV) and neodymium(III) complex with 1,3-diamino-2-propanoltetraacetic acid (H5Hpdta) [Ge(OH)(μ-HHpdta)(μ-OH)Nd(OH)(H2O)3] · H2O has been synthesized for the first time and characterized by physicochemical methods (elemental analysis, X-ray powder diffraction, thermogravimetry, IR spectroscopy, X-ray crystallography). The crystals are monoclinic: a = 9.331(3) A, b= 10.279(4) A, c = 21.474(7) A, β = 94.59(3)°, V = 2053.0(12) A3, Z = 4, space group P21/n, R1 = 0.0245 for 4060 reflections with I > 2σ(I). The compound is built of complex binuclear molecules [Ge(OH)(μ-HHpdta)(μ-OH)Nd(OH)(H2O)3] and water molecules of crystallization. The germanium and neodymium atoms are bridged by the oxygen atom of the hydroxo group (Ge-O, 1.798(2) A; Nd-O, 2.539(2) A) and the deprotonated oxygen atom of the isopropanol group of the HHpdta4− ligand (Fe-O, 1.858(2)A; Nd-O, 2.420(2) A) to form a dimeric molecule. Each coordination sphere (of the Ge atom and of the Nd atom) contains one nitrogen atom (Ge-N, 2.096(3) A; Nd-N, 2.807(2) A) and two carboxylic oxygen atoms from four acetate branches of the octadentate HHpdta4− ligand (av. Ge-O, 1.928(2) A; Nd-O, 2.391(2) A). The coordination polyhedron of the Ge atom is completed to a distorted octahedron by the oxygen atom of the terminal hydroxo group (Ge-O 1.811(2) A), and the polyhedron of the Nd atom is completed to a nine-vertex polyhedron by the oxygen atoms of the terminal hydroxo group (Nd-O 2.494(3) A) and three water molecules (Nd-O, 2.512(3), 2.520(3), and 2.723(3) A). In the crystal structure, the complex molecules and the water molecules of crystallization are joined by a hydrogen bond system.

Ring‐Opening Polymerization of Cyclic Esters by an Enantiopure Heteroscorpionate Rare Earth Initiator

With a sting in its tail: An enantiopure neodymium complex (see scheme) acts as an efficient single-site initiator for the controlled ring-opening polymerization of rac-lactide, forming isotactic polyester. The heteroscorpionate complex was characterized spectroscopically and by X-ray diffraction.

New dinuclear lanthanide(III) complexes based on 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and 2,2′-bipyrimidine

Reaction of mononuclear Ln(fod) 3 chelates (where fod is the anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and Ln = Nd, Eu, Tb and Lu) with potentially bridging ligand 2,2′-bipyrimidine (bpm) in 2:1 mole ratio in ethanol afforded new dinuclear lanthanide complexes of the form [Ln(fod) 3-(μ-bpm)-Ln(fod) 3]. Neodymium complex is one of the rare bipyrimidine-bridged dinuclear complexes. The absorption spectrum of the neodymium complex displays characteristic hypersensitive as well as non-hypersensitive transitions. The excitation of Eu–Eu and Tb–Tb complexes at 355 nm produces an intense red and green luminescence, respectively.

First neodymium(iii) alkyl-carbene complex based on bis(iminophosphoranyl) ligands

Serendipitous deprotonation of bis(iminophosphoranyl)methanide Nd(III) complexes afforded the first alkyl-carbene neodymium complex. Due to the presence of structurally similar methanide and methandiide fragments, this complex features, as evidenced by X-ray crystallographic analysis, Nd-C single and multiple bonds.

Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes

Complexation of neodymium(III) with nitrate was studied at variable temperatures (25, 40, 55, and 70 degrees C) by spectrophotometry and microcalorimetry. The NdNO(3)(2+) complex is weak and becomes slightly stronger as the temperature is increased. The enthalpy of complexation at 25 degrees C was determined by microcalorimetry to be small and positive, 1.5 +/- 0.2 kJ x mol(-1), in good agreement with the trend of the stability constant at variable temperatures. Luminescence emission spectra and the lifetime of Eu(III) in nitrate solutions suggest that inner-sphere and bidentate complexes form between trivalent lanthanides (Nd(3+) and Eu(3+)) and nitrate in aqueous solutions. A specific ion interaction approach was used to obtain the stability constants of NdNO(3)(2+) at infinite dilution and variable temperatures.

Synthesis, spectral and pharmacological studies on lanthanide(III) complexes of 3,5-pyrazoledicarboxylic acid

Complexes of cerium(III), lanthanum(III) and neodymium(III) with 3,5-pyrazoledicarboxylic acid (H3pdc) were synthesized and their compositions determined by elemental analysis. To identify the binding of Ce(III), La(III) and Nd(III) with H3pdc, detailed vibrational analysis was performed comparing experimental vibrational spectra of the ligand and its Ln(III) complexes with theoretically predicted and with literature data from related compounds. Significant differences in the IR and Raman spectra of the complexes were observed as compared to spectra of the ligand. The ligand and the complexes were tested for cytotoxic activities on the chronic myeloid leukemia derived K-562, overexpressing the BCR-ABL fusion protein and the non-Hodgkin lymphoma derived DOHH-2, characterized by an overexpression of the antiapoptotic protein bcl-2 cell lines. The results indicate that the tested compounds exerted considerable cytotoxic activity upon the evaluated cell lines in a concentration dependent manner; we constructed dose-response curves and calculated corresponding IC50 values. The lanthanide complexes exhibited potent cytotoxic activity, even more than cisplatin towards K-562 and DOHH-2 cell lines. In order to elucidate some of the mechanistic aspects of the observed cytotoxic effects, we evaluated whether the established cytotoxicity of the most active complex La(H2pdc) is related to its capacity to induce cell death through apoptosis.

Paramagnetic NMR shift, spectroscopic and molecular modeling studies of lanthanide(III)-morin complexes

Studies on nine-coordinate lanthanide complexes of morin are described. The complexes were characterized by elemental analysis, molar conductance, UV–Vis spectra, IR spectra, thermal analysis and NMR spectra. Molecular modeling studies were also carried out. The complexes are non-electrolytes in DMSO. TGA showed anhydrous nature of the complexes. The electronic spectra of the complexes were recorded in methanol. 1H NMR spectra of lanthanum, praseodymium, neodymium, samarium and dysprosium complexes have been studied in DMSO-d6. The complexes do not dissociate in DMSO and retain their coordination. 1H NMR spectra of paramagnetic and diamagnetic complexes exhibit downfield as well as upfield shifts of morin resonances that shows change in geometry during coordination.