IR luminescence of neodymium(III) and ytterbium(III) ions in complexes with N-alkyl-substituted 2-aminobenzoic acids

The luminescence of neodymium(III) and ytterbium(III) ions in complexes with N-alkyl-substituted 2-aminobenzoic acids has been studied. The luminescence spectra of the Nd(III) complexes show two bands with maxima at 875 and 904 and 1060 nm, and the spectra of the Yb(III) complexes show one band at 980 nm. The introduction of an additional ligand or some surfactants into the Nd(III) and Yb(III) coordination sphere leads to an increase in the luminescence intensity. A correlation between the luminescence intensity of Nd(III) and Yb(III) 2(N-alkylamino)benzoates and the length of the hydrocarbon radical bound to the nitrogen atom has been studied.     

Pyrene-sensitised near-IR luminescence from ytterbium and neodymium complexes

Ytterbium and neodymium have been shown to exhibit sensitised emission following excitation of pyrene chromophores. Sensitised emission is demonstrated in self-assembled complexes and in azamacrocycle derivatives bearing pendent pyrene groups. Energy transfer in these systems is dependent on the nature of the link between the ligand and the complex.     

Quenching of IR luminescence of erbium, neodymium, and ytterbium beta-diketonate complexes by ligand C-H and C-D bonds

The effect of CH and CD quenching on the luminescence lifetime of Er(3+) Nd(3+) and Yb(3+) in the Cs[Ln(HFA)(4)] system has been quantified, and we have shown that for Er(3+) ions the quenching is dominated by the nearest neighbor CH oscillators, whereas for Nd(3+) ions the roles of more distant CH oscillators and nearest neighbor CD oscillators are important.     

Energy transfer between neodymium(III) and ytterbium(III) in transition-metal fluoride (TMFG) glasses

Energy transfer rates between Nd(III) and Yb(III) in glasses of the basic composition 36 PbF₂:24 ZnF₂:35 GaF₃:2 AlF₃;3 YF₃:4 LaF₃ were calculated from donor decay curves, and applied for construction of acceptor luminescence curves. The transfer rates are time dependent and the energy loss by Nd(III) is quantitatively transferred to Yb(III).     

Luminescence of neodymium(III) carboxylate complexes with different ligands

The spectral and luminescent characteristics of neodymium(III) carboxylate complexes with different nitrogen- and phosphorus-containing neutral ligands were studied and the relationship between the intensity of luminescence and the composition of the coordination sphere was established. The most intensive luminescence of neodymium(III) compounds in the IR region was observed from the complexes with toluic and cinnamic acids.     

New cerium(III) and neodymium(III) complexes as cytotoxic agents

The cerium(III) and neodymium(III) complexes of 5‐aminoorotic acid were synthesized and characterized by means of spectral data (IR, Raman, ¹H NMR and ¹³C NMR) and elemental analysis. Significant differences in the IR spectra of the complexes were observed as compared with the spectrum of the ligand. A comparative analysis of the Raman spectra of the complexes with that of the free 5‐aminoorotic acid allowed a straightforward assignment of the vibrations of the ligand groups involved in coordination. ¹H NMR and ¹³C NMR spectra confirmed the formation of the complexes. The ligand and the complexes were tested for the 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 a rexpression of the antiapoptotic protein bcl‐2 cell lines. The results obtained indicate that the tested compounds exerted a considerable cytotoxic activity upon the evaluated cell lines in a concentration‐dependent manner, which enabled the construction of dose–response curves and the calculation of the corresponding IC₅₀ values. Cytotoxicity towards tumor cells was determined for a broad concentration range. The inorganic salts exerted a very weak cytotoxic effect on these cells that is in contrast to the lanthanide complexes, which exhibited potent cytotoxic activity towards K‐562 and DOHH‐2 cell lines. Copyright © 2006 John Wiley & Sons, Ltd.     

Hydroxide complexes of lanthanides-IV ytterbium(III) in perchlorate medium

From the precipitation borderline in the pM'-pC(H) diagram, determined experimentally under CO(2)-free conditions, the stability constants of the mononuclear species of ytterbium hydroxide have been established. The values found are log *beta(1) = -7.7, log *beta(2) = -15.5, log *beta(3) = -23.2, log *beta(4) = -37.5, log *beta(5) = -51.9, log *beta(6) = -66.2 and log *K(S0) = 18.0. The data refer to fresh precipitates, prepared at room temperature (21.5 +/- 0.2 degrees ) in sodium perchlorate medium with an ionic strength of 1. The formation of polynuclear hydroxide complexes has been considered and rejected as unlikely to occur.     

Axial Ligand exchange in chiral macrocyclic ytterbium(III) complexes

We investigate the role of axial ligands on the near-IR-optical and paramagnetic NMR spectra of the complex [YbL](+3) where L is the stereodefined enantiopure chiral macrocycle (L = hexaazapentacyclo[25.3.1.1(12,24).0(4,9).0(19,24)]dotriaconta-1(31),2,10,12,14,16(32),17,25,27,29-decaene). The conformation in solution of the lanthanide complex is characterized by analyzing the pseudocontact 1H NMR shifts and is consistent with X-ray data of single crystal of analogue systems. The macrocycle is confined within a thin equatorial disk, leaving the cation open to at least two axial sites, on the opposite hemispheres. We recorded, assigned, and analyzed the 1H NMR spectra of several species upon changing the anion in solution, calculating the magnetic susceptibility anisotropy tensor for each. Near-IR circular dichroism is used to investigate the solution equilibria involving the competing ligands and to derive a spectroscopic series for Yb.     

Diverse heteroleptic ytterbium(III) thiocyanate complexes by oxidation from bis(thiocyanato)ytterbium(II)

The new ytterbium(II) thiocyanate complex [Yb(NCS)2(thf)2] (1), synthesised by redox transmetallation between [Hg(SCN)2] and ytterbium metal in THF at room temperature, gave monomeric, eight coordinate [Yb-(NCS)2(dme)3] (2, dme = 1,2-dimethoxyethane) on crystallisation from DME, and is a powerful, synthetically useful reductant. Thus, oxidation of 1 with Hg(SCN)2, Hg(C6F5)2/HOdpp (HOdpp = 2,6-diphenylphenol), TlCp (Cp = C5H5 or CH3C5H4), Tl(Ph2pz) (Ph2pz = 3,5-diphenylpyrazolate) and CCl3CCl3 in THF yielded the ytterbium(II) complexes [Yb(NCS)3(thf)4] (3), [Yb-(NCS)2(Odpp)(thf)3](4), [Yb(NCS)2Cp-(thf)3] (Cp = C5H5 (5), CH3C5H4 (6)), [Yb(NCS)2(Ph2pz)(thf)4] (7) and [Yb(NCS)2Cl(thf)4] (8). In the solid state, complexes 4, 6 and 7 were shown by X-ray crystallography to be six, eight and eight coordinate monomers, respectively. Exclusively terminal, N-bound transoid thiocyanate bonding is observed with eta1-Odpp (4), eta5/-C5H4Me (6) and eta2-Ph2Pz (7) ligands attached approximately perpendicular to the N...N vector. The chloride complex 8 is not a molecular species, but consists of discrete, seven coordinate [YbCl2(thf)5] cations and [Yb(NCS)4(thf)3] anions. By contrast, oxidation of 1 with TlO2CPh gave a mixture of [[Yb(NCS)-(O2CPh)2(thf)2]2] (9) and 3 through rearrangement of an initially formed [Yb(NCS)2(O2CPh)] species. The X-ray structure of 9 indicates a dimeric complex with a (Yb(mu-O2CPh)4Yb] core that contains both bridging bidentate and bridging tridentate benzoate groups, and with a terminal N-bound thiocyanate and two THF ligands on each ytterbium. Reduction of Ph2CO with 1 in THF yielded the dinuclear complex [[Yb(NCS)2(thf)3]2(mu-OC(Ph)2C(Ph)2O)] (10), in which two octahedral Yb centres are bridged by a 1,1,2,2-tetraphenylethane-1,2-diolate ligand, derived from reductive coupling of the benzophenone reagent.     

Fluorescence and DNA-binding properties of neodymium(III) and praseodymium(III) complexes containing 1,10-phenanthroline

The binding of neodymium(III) and praseodymium(III) complexes containing 1,10-phenanthroline, [M(phen)2Cl3·OH2] (M=Nd (1), Pr (2)), to DNA has been investigated by absorption, emission, and viscosity measurements. The complexes show absorption decreasing in charge transfer band, fluorescence decrement when bound to DNA. The binding constant Kb has been determined by absorption measurement for both complexes and found to be (6.76±0.12)×10(4) for 1 and (1.83±0.15)×10(4)M(-1), for 2. The fluorescence of [M(phen)2Cl3·OH2] (M=Nd (1), Pr (2)) has been studied in detail. The results of fluorescence titration reveal that DNA has the strong ability to quenching the intrinsic fluorescence of Nd(III) and Pr(III) complexes through the static quenching procedure. The binding site number n, apparent binding constant Kb and the Stern-Volmer constant kSV are determined. Thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), are calculated according to relevant fluorescent data and Van't Hoff equation. The experimental data suggest that the complexes bind to DNA by non-intercalative mode. Major groove binding is the preferred mode of interaction for [M(phen)2Cl3·OH2] (M=Nd (1), Pr (2)) with DNA.     

Sensitized near-IR luminescence of Ln(III) complexes with benzothiazole derivatives

Lanthanide complexes with benzothiazole derivatives (Btz-R, R = OCH(3) and OH) and terpyridine (tpy) ligands were synthesized, and their photophysical properties were precisely investigated. The free Btz-OCH(3) ligand in toluene, excited with UV light, produced the normal emission bands around 410 nm, whereas Btz-OH produced a strong excited-state intramolecular proton transfer (ESIPT) band at 510 nm. The Ln(III) complexes (Ln = Nd, Er, and Yb) exhibited sensitized near-IR luminescence when the Btz-R ligands were excited. The sensitized luminescence quantum yields (Phi(Ln)) of the lanthanide complexes were markedly enhanced by ESIPT: for [Nd(Btz-R)(tpy)] in toluene solution, Phi(Ln) = 0.04% for Btz-OCH(3) and 0.39% for Btz-OH. The sensitized luminescence of the Er(III) complexes (Phi(Ln) = 0.002% for Btz-OCH(3) and 0.009% for Btz-OH) was less efficient than that of the Nd(III) complexes. This difference is due to the smaller energy gap between the emitting and ground levels of the Er(III) ion. The rate constants for the energy transfer from Btz-R to Ln(III) were about approximately 10(9) s(-1), as evaluated by the F?rster resonance energy transfer mechanism.     

Near-infrared luminescence of nine-coordinate neodymium complexes with benzimidazole-substituted 8-hydroxyquinolines

A new class of benzimidazole-substituted 8-hydroxyquinoline ligands has been prepared that contain a monoanionic tridentate N,N,O-coordinating unit. These ligands form charge-neutral lanthanide complexes of the type [Ln(L-R) 3]. nH 2O or [Ln 2(L2) 3]. nH 2O ( n = 1-3) with early lanthanides from La (III) to Gd (III) inclusive. Crystallographic characterization was carried out for 11 complexes with 6 different ligands. In all of these structures, the lanthanide ion was found to be nine-coordinated by three ligands arranged in an "up-up-down" fashion around the metal center. The coordination environment can be described as a tricapped trigonal prism, with N atoms of quinoline rings occupying capping positions. Upon deprotonation of the ligand and complex formation, a new absorption band appears in the visible range of the spectrum with a maximum in the range of 466-483 nm and molar absorption coefficient of (7.2 - 18) x 10 (3) M (-1) cm (-1). Its origin is likely to be an intraligand phenolate-to-pyridyl charge transfer transition centered on the 8-hydroxyquinolate chromophore. Upon excitation in ligand absorption bands, new Nd (III) complexes display characteristic metal-centered luminescence in the near-infrared region from 850 to 1450 nm with quantum yields and lifetimes in solid state at room temperature as high as 0.34% and 1.2 mus, respectively.     

Lanthanum(III), cerium(III), praesodymium(III), neodymium(III) and samarium(III) chloride triethyl phosphate complexes

Summary Five new MCl₃ · TEP compounds, where M = Ce, Pr, Nd and Sm, and LaCl₃ 2 TEP have been prepared. The magnetic susceptibility and i.r. spectra of these complexes are discussed.Reprints of this paper are not available.     

Synthesis,characterization and cytotoxicity evaluation of new cerium(III), lanthanum(III) and neodymium(III) complexes

Complexes of cerium(III), lanthanum(III) and neodymium(III) with coumarin‐3‐carboxylic acid (HCCA) were synthesized by mixing of equimolar amounts of the respective metal nitrates and coumarin‐3‐carboxylic acid in ethanol. The complexes were characterized and identified by elemental analysis, IR and Raman spectroscopy. DTA and TGA were applied to study the compositions of the compounds. The vibrational study showed bidentate coordination of CCA^? to Ln(III) ions through the carbonyl oxygen and the carboxylic oxygen atoms. The newly synthesized compounds were assayed for cytotoxicity against SKW‐3, HL‐60 and Reh cells. The complexes of cerium(III) and lanthanum(III) showed marginal cytotoxic activity against SKW‐3 and Reh cells as compared with the inorganic salts at concentration 200 µM . The complex of neodymium(III) induced approximately 50% reduction of the survival HL‐60 and SKW‐3 cells at concentration 200 µM . Copyright © 2007 John Wiley & Sons, Ltd.     

Controlled synthesis and upconverted avalanche luminescence of cerium(III) and neodymium(III) orthovanadate nanocrystals with high uniformity of size and shape

We report on controlled synthesis of uniform LnVO4 (Ln = Ce and Nd) nanocrystals (NCs) with square-plate and H-shaped morphologies in nanosized reverse microemulsion reactors, via a facile solvo/hydrothermal strategy. The NCs were thoroughly characterized by X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), infrared absorption spectroscopy, and photoluminescence. Possible mechanisms of the rare-earth orthovanadate NC growth and size and shape evolution are proposed. A unique upconverted avalanche luminescence property pertaining to the NCs has been discovered, systematically studied, and mechanistically discussed. Our work combines synthetic and optical studies of the NCs and lays a foundation for reinventing their applications in optoelectronics among others.     

Synthesis,structural characterization and biological studies of neodymium(III) and samarium(III) complexes with mercaptotriazole Schiff bases

A series of neodymium(III) and samarium(III) complexes of type [Ln(L)Cl(H₂O)₃] have been synthesized with Schiff bases (LH₂) derived from 3‐(phenyl/substituted phenyl)‐4‐amino‐5‐mercapto‐1,2,4‐triazoles and isatin. The structures of the complexes were established using elemental analysis, molar conductivities, magnetic moments, infrared, NMR (¹H, ¹³C) and UV–visible spectra, X‐ray diffraction and mass spectrometry. The thermal behaviour of these compounds under non‐isothermal conditions was investigated using thermogravimetry and differential thermogravimetry. The intermediates obtained at the end of various thermal decomposition steps were identified from elemental analysis and infrared spectral studies. All the ligands and their complexes were also screened for their antibacterial activity against Staphylococcus aureus and Bacillus subtilis and antifungal activity against Aspergillus niger, Aspergillus flavus and Colletotrichum capsici. The screening results were correlated with the structural features of the compounds. Copyright © 2015 John Wiley & Sons, Ltd.