Yb Complexes Research Articles

Lanthanide Speciation in Potential SANEX and GANEX Actinide/Lanthanide Separations Using Tetra-N-Donor Extractants

Lanthanide(III) complexes with N-donor extractants, which exhibit the potential for the separation of minor actinides from lanthanides in the management of spent nuclear fuel, have been directly synthesized and characterized in both solution and solid states. Crystal structures of the Pr(3+), Eu(3+), Tb(3+), and Yb(3+) complexes of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BTPhen) and the Pr(3+), Eu(3+), and Tb(3+) complexes of 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'-bypyridine (CyMe4-BTBP) were obtained. The majority of these structures displayed coordination of two of the tetra-N-donor ligands to each Ln(3+) ion, even when in some cases the complexations were performed with equimolar amounts of lanthanide and N-donor ligand. The structures showed that generally the lighter lanthanides had their coordination spheres completed by a bidentate nitrate ion, giving a 2+ charged complex cation, whereas the structures of the heavier lanthanides displayed tricationic complex species with a single water molecule completing their coordination environments. Electronic absorption spectroscopic titrations showed formation of the 1:2 Ln(3+)/L(N4-donor) species (Ln = Pr(3+), Eu(3+), Tb(3+)) in methanol when the N-donor ligand was in excess. When the Ln(3+) ion was in excess, evidence for formation of a 1:1 Ln(3+)/L(N4-donor) complex species was observed. Luminescent lifetime studies of mixtures of Eu(3+) with excess CyMe4-BTBP and CyMe4-BTPhen in methanol indicated that the nitrate-coordinated species is dominant in solution. X-ray absorption spectra of Eu(3+) and Tb(3+) species, formed by extraction from an acidic aqueous phase into an organic solution consisting of excess N-donor extractant in pure cyclohexanone or 30% tri-n-butyl phosphate (TBP) in cyclohexanone, were obtained. The presence of TBP in the organic phase did not alter lanthanide speciation. Extended X-ray absorption fine structure data from these spectra were fitted using chemical models established by crystallography and solution spectroscopy and showed the dominant lanthanide species in the bulk organic phase was a 1:2 Ln(3+)/L(N-donor) species.

Lanthanide complexes with substituted naphtholate ligands: extraordinary bright near-infrared luminescence of ytterbium

A series of Pr, Nd, Ho, Er, Tm, and Yb complexes with 3-(2-benzoxazol-2-yl)-2-naphtholate and 3-(2-benzothiazol-2-yl)-2-naphtholate ligands was synthesized. The structure, as well as the photo- and electroluminescent properties of these complexes were studied. An extraordinary bright emission of Yb3+ was detected. To explain the phenomenon, a novel excitation mechanism involving intramolecular electron transfer was proposed.

Synthesis, Characterization, and Photophysical Properties of First Heterobinuclear Zn-Ln (Ln = La, Nd, Eu, Gd, Tb, Er, and Yb) Complexes Based on Asymmetric Schiff-Base Ligand

ABSTRACT With a novel asymmetric Schiff-base zinc complex ZnL(H 2 L = N-(3-methoxysalicylidene)-N’-(5-(4-cyanophenyl)-3-methoxysalicylidene)phenylene-1, 2-diamine), obtained from phenylene-1, 2-diamine, 3-methoxysalicylaldehyde, and 5-(4-cyanophenyl)-3-methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn-Ln complexes [ZnLnL(NO 3 ) 3 (CH 3 CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were obtained by further reaction with Ln(NO3)3 · 6H2O. Photophysical studies of these complexes show that the strong and characteristic NIR luminescence with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff-base ligand due to effective intramolecular energy transfer.

Supramolecular assemblies with water-soluble p-sulfonatothiacalix[6]arene lanthanide complexes: one-dimensional ‘ladder-type’ coordination polymers and one-dimensional hydrogen-bonded polymers

Crystals of La and Ce complexes of water-soluble p-sulfonatothiacalix[6]arenes showed that thiacalixarene molecules adopt a 1,2,3-alternate conformation. In contrast, crystals of Eu, Tb, Tm, Yb, and Lu complexes of p-sulfonatothiacalix[6]arenes indicated that thiacalixarene molecules maintain an ‘up-down’ double partial-cone conformation. In the extended structures of the La and Ce complexes, a one-dimensional ‘ladder-type’ coordination polymer was formed via direct coordination of the sulfonate groups of the thiacalixarene molecules to the aquated metal cations. Three-dimensional supramolecular network assemblies are constructed from the piles of ‘ladder-type’ polymers formed via hydrogen bonds, O⋯O and S⋯S interactions, and S–π interactions. In contrast, the extended structures of the Eu, Tb, Tm, Yb, and Lu complexes form via mutually supporting intermolecular π–π stacking, S–π interactions, and hydrogen-bonding interactions between two differently directed polymers.

A comparison of sensitized Ln(iii) emission using pyridine- and pyrazine-2,6-dicarboxylates – part II

The synthesis, X-ray structures and photophysical properties of several new Ln(III) complexes with the dianion of pyrazine-2,6-dicarboxylic acid (H(2)PYZ) that demonstrate excellent stability and solubility in non-aqueous solution are reported, and compared to structurally analogous complexes derived from pyridine-2,6-dicarboxylic acid (H(2)DPA). The Eu(III) and Yb(III) complexes demonstrate efficient metal centered luminescence in the visible and Near Infra-Red (NIR) regions, respectively. Low temperature (77 K) phosphorescence measurements using the corresponding Gd(III) complex has allowed the photophysical properties of the sensitizer to be rationalized, together with corresponding TD-DFT studies for a model complex. Lastly, we have evaluated the sensitization efficiencies for these complexes, and have undertaken femtosecond transient absorption (TA) measurements in order to evaluate the relative importance of the intersystem crossing and energy transfer processes involved with sensitized Ln(III) emission via the antennae effect.

Efficient sensitized emission in Yb(iii) pentachlorotropolonate complexes

New Yb(III) complexes based on the pentachlorotropolonate (pctrop) ligand show enhanced infrared emission when excited in the orange organic chromophore. Yb(pctrop)(3)(DMF-d(7))(2) presents the highest reported quantum yield for a nonfluorinated infrared-emitting organolanthanide complex.

Energy migration toward a dye in nanoparticles from complexes with short fluorescent state lifetimes

We have studied regular features of the fluorescence sensitization (cofluorescence) of coumarin 30 and rhodamine 6G introduced into nanoparticles from complexes Ln(PhBTA) 3 phen, where PhBTA is pphe� nylbenzoyltrifluoroacetone and Ln is a triply charged Pr, Nd, Sm, Eu, Er, or Yb ion, which absorbs in the fluorescence range of ligands of complexes and dyes. We show that both the cofluorescence intensities (Icofl) of rhodamine 6G in nanoparticles from Sm and Eu complexes and the behavior of intensity Icofl on the con� tent of rhodamine 6G coincide with the corresponding data obtained for nanoparticles from La and Lu com� plexes doped with rhodamine 6G molecules. A considerable decrease in I cofl of rhodamine 6G is observed only in nanoparticles from complexes Nd(PhBTA)3phen. In nanoparticles from Pr, Nd, Sm, Eu, Er, and Yb complexes doped with coumarin 30, it has been observed that, depending on the choice of the central ion, Icofl of coumarin 30 is 2 to 80 times lower compared to Icofl of the dye in nanoparticles from La and Lu com� plexes. A separate analysis of the influence of these ions on the energy transfer from complexes to coumarin 30 and on the fluorescence intensity of coumarin 30 incorporated into nanoparticles from these ions showed that a decrease in Icofl of coumarin 30 by a factor of 2-20 occurs due to the reduction of τfl of ligands of com� plexes under the influence of the interaction with Pr, Nd, Sm, Eu, Er, and Yb ions. Since τfl of complexes La(PhBTA)3phen is ~2 ps, while that of complexes Gd(PhBTA)3phen is ~1 ps, then, in nanoparticles with a maximal decrease in I cofl of coumarin 30, τ fl of complexes is reduced to ~0.1 ps. It has been found that, in nanoparticles from complexes with this τ fl , energy migration over complexes takes place. However, as distinct from nanoparticles from La, Lu, and Y complexes, the free path length of singlet excitons in nanoparticles from complexes of absorbing ions is smaller than the nanoparticle size.

IR luminescence of mixed-ligand complexes of Nd(III), Yb(III), and Er(III) with dibenzoylmethane and 1,2,4-triazoles

The synthesis and photoluminescence spectra of mixed-ligand complexes of Nd(III), Yb(III), and Er(III) with dibenzoylmethanate anion as the principal ligand and functionalized 1,2,4-triazoles and spacer bis-triazoles as ancillary ligands were described.

Chiral Benzamidinate Ligands in Rare‐Earth‐Metal Coordination Chemistry

The treatment of the recently reported potassium salt (S)-N,N'-bis-(1-phenylethyl)benzamidinate ((S)-KPEBA) and its racemic isomer (rac-KPEBA) with anhydrous lanthanide trichlorides (Ln = Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)-PEBA}(3)Sm], bis(amidinate) complexes [{Ln(PEBA)(2)(μ-Cl)}(2)] (Ln = Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl)(2)(thf)(n)] (Ln = Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)-amido complexes [{(S)-PEBA}(2)Ln{N(SiMe(3))(2)}] (Ln = Y, Lu) were synthesized by an amine-elimination reaction and salt metathesis. All of these chiral bis- and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac-PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)-PEBA}(2)Ln{N(SiMe(3))(2)}] (Ln = Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound.

Lanthanide Complexes Based on a Diazapyridinophane Platform Containing Picolinate Pendants

A new macrocyclic ligand, N,N'-bis[(6-carboxy-2-pyridyl)methyl]-2,11-diaza[3.3](2,6)pyridinophane (H(2)BPDPA), was prepared, and its coordination properties toward the Ln(III) ions were investigated. The hydration numbers (q) obtained from luminescence lifetime measurements in aqueous solution of the Eu(III) and Tb(III) complexes indicate that they contain one inner-sphere water molecule. The structure of the complexes in solution has been investigated by (1)H and (13)C NMR spectroscopy, as well as by theoretical calculations performed at the density functional theory (B3LYP) level. The minimum-energy conformation calculated for the Yb(III) complex is in excellent agreement with the experimental structure in solution, as demonstrated by analysis of the Yb(III)-induced paramagnetic (1)H shifts. Nuclear magnetic relaxation dispersion (NMRD) profiles and (17)O NMR measurements recorded on solutions of the Gd(III) complex were used to determine the parameters governing the relaxivity. The results show that this system is endowed with a relatively fast water-exchange rate k(ex)(298) = 63 × 10(6) s(-1). Thermodynamic stability constants were determined by pH-potentiometric titration at 25 °C in 0.1 M KCl. The stability constants, which fall within the range logK(LnL) = 12.5-14.2, point to a relatively low stability of the complexes primarily as a consequence of the low basicity of the ligand.

Heterobinuclear Zn-Ln (Ln = La, Nd, Eu, Gd, Tb, Er and Yb) complexes based on asymmetric Schiff-base ligand: synthesis, characterization and photophysical properties

With a novel asymmetric Schiff-base zinc complex ZnL (H2 L = N-(3-methoxysalicylidene)-N'-(5-bromo-3-methoxysalicylidene)phenylene-1,2-diamine), obtained from phenylene-1,2-diamine, 3-methoxysalicylaldehyde and 5-bromo-3-methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn-Ln complexes [ZnLnL(NO3 )3 (CH3 CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were synthesized by the further reaction with Ln(NO3 )3 ·6H2 O, and characterized by Fourier transform-infrared, fast atom bombardment mass spectroscopy and elemental analysis. Photophysical studies of these complexes show that the strong and characteristic near-infrared luminescence of Nd(3+) , Yb(3+) and Er(3+) with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff-base ligand due to effective intramolecular energy transfer; the other complexes do not show characteristic emission due to the energy gap between the chromophore and lanthanide ions.

Functionalization of BINOL and application in the homo- and heterogeneous enantioselective epoxidation of α,β-unsaturated ketones

The selective functionalization of BINOL derivatives with 3-(dimethylamino)prop-1-yn-1-yl is described. The corresponding La and Yb complexes were evaluated toward the epoxidation of α,β-unsaturated ketones. The Yb-complexes display the highest catalytic activity and selectivity, affording the expected chiral epoxides in quantitative yields and up to 90% ee in homogeneous conditions, and 93% ee when supported on silica gel.

Binding analysis of ytterbium(III) complex containing 1,10-phenanthroline with DNA and its antimicrobial activity

To evaluate the biological preference of [Yb(phen)2(OH2)Cl3](H2O)2 (phen is 1,10-phenanthroline) for DNA, interaction of Yb(III) complex with DNA in Tris–HCl buffer is studied by various biophysical and spectroscopic techniques which reveal that the complex binds to DNA. The results of fluorescence titration reveal that [Yb(phen)2(OH2)Cl3](H2O)2 has strongly quenched in the presence of DNA. The binding site number n, apparent binding constant K b, and the Stern–Volmer quenching constant K SV are determined. ΔH 0, ΔS 0, and ΔG 0 are obtained based on the quenching constants and thermodynamic theory (ΔH 0 > 0, ΔS 0 > 0, and ΔG 0 < 0). The experimental results show that the Yb(III) complex binds to DNA by non-intercalative mode. Groove binding is the preferred mode of interaction for [Yb(phen)2(OH2)Cl3](H2O)2 to DNA. The DNA cleavage results show that in the absence of any reducing agent, Yb(III) complex can cleave DNA. The antimicrobial screening tests are also recorded and give good results in the presence of Yb(III) complex.

Erratum to “Structure and sensitized near-infrared luminescence of Yb(III) complexes with sulfonylamidophosphate type ligand” [J. Photochem. Photobiol. A: Chem. 217 (2011) 1–9

Erratum to “Structure and sensitized near-infrared luminescence of Yb(III) complexes with sulfonylamidophosphate type ligand” [J. Photochem. Photobiol. A: Chem. 217 (2011) 1–9

Polyphenylcyclopentadienyl complexes of rare earth elements

Reaction of LnCl3(thf)x (Ln = Y, La, Yb, Lu) with NaCpPhn (CpPhn = 1,3-Ph2C5H3, 1,2,4-Ph3C5H2, Ph4C5H) leads to formation of monocyclopentadienyl dichloride complexes Yb(Ph2C5H3)Cl2(thf)3 (1), Ln(Ph3C5H2)Cl2(thf)3 (Ln = Y (2), Lu (3)), La(Ph4C5H)Cl2(thf)3 (4). Molecular structures of 1, 2 and the polynuclear complex [(Ph3C5H2)3Lu4(Cl)7(O)(thf)3] (5), which is a partial hydrolysis product of 3, have been established by the X-ray method.

Cation effect on the crystal structure of polynuclear complexes with 2,2′-oxydiacetate as bridging ligand

Using the flexible ligand oxydiacetic acid (H2oda), nine heterodimetallic polymers [{Ca(H2O)6}{CaLn(oda)3}2]·xH2O (Ln=Y, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu) were synthesized and structurally characterized. The syntheses were performed in aqueous solution by reaction of the ligand and salts of the two ions. They are isostructural and possess a highly ordered 3D structure with [CaLn(oda)3]− as building blocks. The charge is balanced with [Ca(H2O)6]2+ ions which occupy the holes of the anionic framework. The complexes are thermally stable up to 250°C. Magnetic susceptibility measurements of Yb and Eu complexes show deviations from the Curie law mainly owing to the split of the ground term due to the ligand field and to the depopulating of paramagnetic excited states in the Yb and Eu compounds, respectively.

Preparation, Structure and Near-infrared Luminescent Property of Yb(III) Complex with 2,4,6-Pyridinetricarboxylic Acid

A rare earth ytterbium complex with 2,4,6-pyridinetricarboxylic acid (H(3)pta) has been synthesized by hydrothermal method, the formula is {[Yb(2)(pta)(2)(H(2)O)(3)]·H(2)O}(n). The complex crystallized in monoclinic system, P2(1)/c space group with lattice parameters a = 11.6556(19)Å, b = 7.8364(12), c = 22.020(4), α = γ = 90º, β = 92.120(3), Z = 4, GOF = 1.026, R1 = 0.0334, wR2 = 0.0660. The pta anions connect four rare earth Yb(III) ions with two different coordination modes. The complex exhibit intense characteristic near-infrared luminescence of Yb(III) ions at 990 nm with excitation of UV-rays.

Rare earth thiocyanate complexes with 18-crown-6 co-ligands

Reaction of [Ln(NCS)3(THF)4]2 or [Yb(NCS)3(THF)4] with 18-crown-6 yields the moisture-stable [Ln(NCS)3(18-crown-6)] (Ln=La, Nd, Dy, Yb) complexes. Although the Ln contraction does not affect the coordination number, the crown ether is decreasingly folded with decreasing ion size.

Bis(imidazolin-2-iminato) Rare Earth Metal Complexes: Synthesis, Structural Characterization, and Catalytic Application

Reaction of anhydrous rare earth metal halides MCl(3) with 2 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH) and 2 equiv of trimethylsilylmethyl lithium (Me(3)SiCH(2)Li) in THF furnished the complexes [(Im(Dipp)N)(2)MCl(THF)(n)] (M = Sc, Y, Lu). The molecular structures of all three compounds were established by single-crystal X-ray diffraction analyses. The coordination spheres around the pentacoordinate metal atoms are best described as trigonal bipyramids. Reaction of YbI(2) with 2 equiv of LiCH(2)SiMe(3) and 2 equiv of the imino ligand Im(Dipp)NH in tetrahydrofuran did not result in a divalent complex, but instead the Yb(III) complex [(Im(Dipp)N)(2)YbI(THF)(2)] was obtained and structurally characterized. Treatment of [(Im(Dipp)N)(2)MCl(THF)(n)] with 1 equiv of LiCH(2)SiMe(3) resulted in the formation of [(Im(Dipp)N)(2)M(CH(2)SiMe(3))(THF)(n)]. The coordination arrangement of these compounds in the solid state at the metal atoms is similar to that found for the starting materials, although the introduction of the neosilyl ligand induces a significantly greater distortion from the ideal trigonal-bipyramidal geometry. [(Im(Dipp)N)(2)Y(CH(2)SiMe(3))(THF)(2)] was used as precatalyst in the intramolecular hydroamination/cyclization reaction of various terminal aminoalkenes and of one aminoalkyne. The complex showed high catalytic activity and selectivity. A comparison with the previously reported dialkyl yttrium complex [(Im(Dipp)N)Y(CH(2)SiMe(3))(2)(THF)(3)] showed no clear tendency in terms of activity.

Hetero-binuclear near-infrared (NIR) luminescent ZnLn (Ln = Nd, Yb or Er) complexes self-assembled from the benzimidazole-based ligand

Abstract With the [Zn(HL)2(Py)] compound from the benzimidazole-based ligand H2L (H2L: 2-(1H-benzo[d]imidazol-2-yl)-6-methoxyohenol) as the precursor, the series of four hetero-binuclear ZnLn arrayed complexes [ZnLn(HL)2(Py)(NO3)3] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3; Ln = Gd, 4) have been obtained by the further reaction with Ln(NO3)3·6H2O, respectively. The result of their photophysical properties shows that the strong and characteristic NIR luminescence of Nd3 + or Yb3 + ion with emissive lifetimes in microsecond range, has been sensitized from the excited state (1LC and 3LC) of the benzimidazole-based ligand.