Rare earth fluoride nano-/microstructures: hydrothermal synthesis, luminescent properties and applications.

Rare earth fluoride materials have attracted wide interest and come to the forefront in nanophotonics due to their distinct electrical, optical and magnetic properties as well as their potential applications in diverse fields such as optical telecommunication, lasers, biochemical probes, infrared quantum counters, and medical diagnostics. This review presents a comprehensive overview of the flourishing field of rare earth fluorides materials in the past decade. We summarize the recent research progress on the preparation, morphology, luminescent properties and application of rare earth fluoride-based luminescent materials by hydrothermal systems. Various rare earth fluoride materials are obtained by fine-tuning of experimental conditions, such as capping agents, fluoride source, acidity, temperature and reaction time. The controlled morphology, luminescent properties and application of the rare earth fluorides are briefly discussed with typical examples.

Methylidene rare-earth-metal complex mediated transformations of C=N, N=N and N-H bonds: new routes to imido rare-earth-metal clusters.

Three new patterns of reactivity of rare-earth metal methylidene complexes have been established and thus have resulted in access to a wide variety of imido rare-earth metal complexes [L3Ln3(µ2-Me)3(µ3-Me)(µ-NR)] (L = [PhC(NC6H3iPr2-2,6)2](-); R = Ph, Ln = Y (2 a), Lu (2 b); R = 2,6-Me2C6H3, Ln = Y (3 a), Lu (3 b); R = p-ClC6H4, Ln = Y (4 a), Lu (4 b); R = p-MeOC6H4, Ln = Y (5 a), Lu (5 b); R = Me2CHCH2CH2, Ln = Y (6 a), Lu (6 b)) and [{L3Lu3(µ2-Me)3(µ3-Me)}2(µ-NR'N)] (R' = (CH2)6 (7 b), (C6H4)2 (8 b)). Complex 2 b was treated with an excess of CO2 to give the corresponding carboxylate complex [L3Lu3(µ-η(1):η(1)-O2CCH3)3(µ-η(1):η(2)-O2C-CH3)(µ-η(1):η(1):η(2)-O2CNPh)] (9 b) easily. Complex 2 a could undergo the selective µ3-Me abstraction reaction with phenyl acetylene to give the mixed imido/alkynide complex [L3Y3(µ2-Me)3(µ3-η(1):η(1):η(3)-NPh)(µ3-C≡CPh)] (10 a) in high yield. Treatment of 2 with one equivalent of thiophenol gave the selective µ3-methyl-abstracted products [L3Ln3(µ2-Me)3(µ3-η(1):η(1):η(3)-NPh)(µ3-SPh)] (Ln = Y (11 a); Lu (11 b). All new complexes have been characterized by elemental analysis, NMR spectroscopy, and most of the structures confirmed by X-ray diffraction.

Synthesis, structure and spectroscopic properties of rare earth complexes with a new aryl amide 2,2'-bipyridine derivative.

Solid complexes of rare earth nitrates and picrates with a new aryl amide ligand 3.3'-bis(benzylamido)-2,2'-bipyridine (L) were synthesized and characterized by elemental analysis, IR and molar conductivity measurements. The molecular structures of the complex [TbL(2)(NO(3))(3)H(2)O].2H(2)O have been determined by single-crystal X-ray diffraction. The fluorescent properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state were also investigated in detail. Under the excitation, these complexes exhibited characteristic emissions of europium and terbium ions. It is worth noting that the nature of the anion has a great effect upon the composition of the complexes as well as emission properties of them.

Synthesis, characterization and luminescent properties of new highly luminescent organic ligand and complexes of trivalent rare earth.

A novel ligand with two carboxylic groups has been synthesized. The composition and structure of the ligand were characterized by IR, (1)H NMR and MS spectrometry. The highly luminescent intensity complexes were prepared with the ligand and phen. The IR, solid state (13)C NMR and fluorescent spectra of the complex were studied. IR absorption spectra indicate that the ligand is coordinated to the Eu(3+) ion, and chemical bonds are formed between Eu(3+) ion and nitrogen atoms of phen. The fluorescent spectra illustrate that the complex has an excellent luminescence, indicating the ligand favors energy transfer to the emitting energy level of Eu(3+). The influences of pH and reaction solvent on the fluorescence intensity of the complex were also discussed.

Synthesis and infrared and fluorescent spectra of rare earth complexes with a new amide ligand.

Solid complexes of rare earth nitrates and picrates with a new amide ligand, 1,6-bis[(2'-benzylaminoformyl)phenoxyl]hexane (L) have been prepared. These complexes are characterized by elemental analysis, UV-vis spectra and IR spectra. The fluorescent and luminescent properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state are also investigated. Under the excitation of UV light, these complexes except Tb(III) picrate complex exhibit characteristic emission of europium and terbium ions. The influence of the counter anion on the fluorescent intensity is also discussed.

Synthesis and characterization of dinuclear rare-earth complexes supported by amine-bridged bis(phenolate) ligands and their catalytic activity for the ring-opening polymerization of l-lactide.

Reactions of amine-bridged bis(phenolate) protio-ligands N,N-bis(3,5-di-tert-butyl-2-hydroxybenzyl)aminoacetic acid (L(1)-H3) and N,N-bis[3,5-bis(α,α'-dimethylbenzyl)-2-hydroxybenzyl]aminoacetic acid (L(2)-H3), with 1 equiv. M[N(SiMe3)2]3 (M = La, Nd, Sm, Gd, Y) in THF at room temperature yielded the neutral rare-earth complexes [M2(L)2(THF)4] (L = L(1), M = La (), Nd (), Sm (), Gd (), Y (); L = L(2), M = La (), Nd (), Sm (), Gd (), Y ()). All of these complexes were characterized by single-crystal X-ray diffraction, elemental analysis and in the case of yttrium and lanthanum complexes, (1)H NMR spectroscopy. The molecular structure of revealed dinuclear species in which the eight-coordinate lanthanum centers were bonded to two oxygen atoms of two THF molecules, to three oxygen atoms and one nitrogen atom of one L(1) ligand, and two oxygen atoms of the carboxyl group of another. Complexes were also dinuclear species containing seven-coordinate metal centers similar to , albeit with bonding to one rather than two carboxyl group oxygens of another ligand. Further treatment of with excess benzyl alcohol provided dinuclear complex [La2(L(1))2(BnOH)6] (), in which each lanthanum ion is eight-coordinate, bonded to three oxygen atoms and one nitrogen atom of one ligand, three oxygen atoms of three BnOH molecules, as well as one oxygen atom of bridging carboxyl group of the other ligand. In the presence of BnOH, complexes efficiently catalyzed the ring-opening polymerization of l-lactide in a controlled manner and gave polymers with relatively narrow molecular weight distributions. The kinetic and mechanistic studies associated with the ROP of l-lactide using /BnOH initiating system have been performed.

An atomic basis of cancer (V): A new marker in animal tumors.

Particle-induced X-ray emission (PIXE) analysis can be applied to mark (or to localize) a cancer lesion in a benign environment in test animals. We synthesized hematoporphyrin derivative (HPD) with rare earth metals to form lanthanide-HPD to enhance the localizing efficiency. The sensitive PIXE detection of trace elements in amounts on the order of nanograms or less could possibly be used to probe carcinogenesis at the level of the cell. To explain the present approach, we present the results of an experiment in which we used paraseodynium-HPD localizer.

Sonochemical synthesis of mesoporous transition metal and rare earth oxides.

Straight-extended layered mesostructures based on transItion metal (Fe, Cr) and rare earth (Y, Ce, La, Sm, Er) oxides are synthesized by sonication for 3 h. After a longer period of sonication (6 h), hexagonal mesostructures based on Y- and Er-oxides are obtained. The surface areas of the Y-based hexagonal mesophases before and after extraction are 46.5, 256 m2/g, respectively. For Er-based hexagonal mesophases, the surface areas before and after extraction are 157 and 225 m2/g. The pore sizes after extraction are 5.0 and 2.2 nm for Y- and Er-based mesophases, respectively. Hexagonal mesostructures are also obtained for Zr-based material after sonication for 3 h and the hexagonal structure is still maintained after calcinations at 400 degrees C for 4 h, although the surface area is only 35 m2/g.

[Synthesis and characterization of mixed ligand complexes rare earth with 2,3-dimethoxylbenzoic acid and 1,10-phenanthroline].

The quaternary mixed anion of rare earth with 2,3-dimethoxylbenzoic acid and 1,10-phenanthroline has been synthesized from the water-ethanol solution. Elemental analysis shows that the complexes general formula is RE(2,3-DMOBA)2NO3Phen (RE = La, Nd, Eu, Dy). The complexes are characterized by IR, UV, TG-DTA analysis. Nu2 + nu5, nu2 + nu6 of NO3- are observed in 1772 and 1737 cm(-1) in IR spectra of complexes, it shows that NO3- group is in a bridging-chelating mode in which two O atoms chelate to RE3+ ions. UV spectra of ligand and complexes are different, it shows that ligand 2,3-dimethoxylbenzoate and 1,10-phenanthroline coordinate to RE3+ ions. Visible absorption spectra of Nd(2,3-DMOBA)2NO3Phen show that hypersensitive transition of neodymium.

Syntheses of new rare earth complexes with carboxymethylated polysaccharides and evaluation of their in vitro antifungal activities.

In the present paper, La, Eu and Yb were selected to represent light, middle and heavy rare earths to form complexes with polysaccharides through chelating coordination of carboxyl groups, which were added into polysaccharide chains by means of carboxymethylation. Their antifungal activities against plant pathogenic fungi were evaluated using growth rate method. These rare earth complexes exhibited various antifungal activities against the tested fungi, depending on rare earth elements, polysaccharide types and fungal species. Among these three metal elements (i.e. La, Eu and Yb), Yb formed the complexes with the most effective antifungal properties. Furthermore, the results showed that ligands of carboxymethylated polysaccharides played a key role in promoting cytotoxicity of the rare earth complexes. Carboxymethylated Ganoderma applanatum polysaccharide (CGAP) was found to be the most effective ligand to form complexes with antifungal activities, followed by carboxymethylated lentinan (CLNT) and carboxymethylated Momordica charantia polysaccharide (CMCP).

Sensing using rare-earth-doped upconversion nanoparticles.

Optical sensing plays an important role in theranostics due to its capability to detect hint biochemical entities or molecular targets as well as to precisely monitor specific fundamental psychological processes. Rare-earth (RE) doped upconversion nanoparticles (UCNPs) are promising for these endeavors due to their unique frequency converting capability; they emit efficient and sharp visible or ultraviolet (UV) luminescence via use of ladder-like energy levels of RE ions when excited at near infrared (NIR) light that are silent to tissues. These features allow not only a high penetration depth in biological tissues but also a high detection sensitivity. Indeed, the energy transfer between UCNPs and biomolecular or chemical indicators provide opportunities for high-sensitive bio- and chemical-sensing. A temperature-sensitive change of the intensity ratio between two close UC bands promises them for use in temperature mapping of a single living cell. In this work, we review recent investigations on using UCNPs for the detection of biomolecules (avidin, ATP, etc.), ions (cyanide, mecury, etc.), small gas molecules (oxygen, carbon dioxide, ammonia, etc.), as well as for in vitro temperature sensing. We also briefly summarize chemical methods in synthesizing UCNPs of high efficiency that are important for the detection limit.

Sensitized room-temperature luminescence in reverse micelles using lanthanide counterions as acceptors.

The analytical usefulness of sensitized room-temperature luminescence in reverse micelles using lanthanide counterions is examined. The technique is based on the unique luminescent properties of tripositive lanthanide metal ions as counterions for the surfactant and the molecular organization produced by reverse micelles. After excitation, the analyte molecule transfers its triplet-state energy to an acceptor molecule (lanthanide), which subsequently emits luminescence. Two surfactants with different lanthanide counterions have been synthesized and characterized by spectroscopic and mass spectrometric techniques. When compared to the lanthanide salt, the sensitized luminescence of the lanthanide surfactant is substantially enhanced. The exact locations of the analyte and the counterion in the micellar system are discussed. The efficiencies of energy transfer for the two surfactants are compared.

Disulfide-tethered solid supports for synthesis of photoluminescent oligonucleotide conjugates: hydrolytic stability and labeling on the support.

Several new disulfide-tethered solid supports (S1-S5) were synthesized, and their resistance against ammonolysis was tested. Among these supports, only the one bearing an N-[15-[(4, 4'-dimethoxytrityl)oxy]-12,13-dithiapentadecanoyl] linker (S4b) tolerated ammonolysis and exhibited properties compatible with the oligonucleotide synthesis by phosphoramidite strategy. The applicability of this disulfide linker structure in postsynthetic oligonucleotide labeling on the support was demonstrated by introduction of two photoluminescent lanthanide chelates or two dansyl groups to the N4-(6-aminohexyl) amino-modified cytosine residues at the 5' end of the oligonucleotide sequence. Subsequent release of the resulting conjugates as their 3'-phosphates was achieved by reductive cleavage of the disulfide bond and precipitation of the conjugate from the solution with ethanol. The fluorescently tagged oligomer obtained showed hybridization properties similar to those of oligonucleotides labeled in solution.

Syntheses and properties of luminescent lanthanide chelate labels and labeled haptenic antigens for homogeneous immunoassays.

Lanthanide chelate labels containing substituted 4-(arylethynyl)pyridine as the chromogenic moiety and iminobis(acetic acid) groups as the chelating part were synthesized. N-Succinimidyl esters of the carboxy derivatives of thyroxine and progesterone were prepared and coupled to the aliphatic amino groups of the synthesized lanthanide chelates. The luminescence properties of the chelates and labeled haptenic antigens were measured in ethanol and in an aqueous buffer containing either albumin or detergents as luminescence-modulating compounds. The energy transfer enhanced ion luminescence of the derivatives containing a para-amino-substituted phenyl ring showed particularly strong dependence on environmental changes, which makes these derivatives well suited for homogeneous time-resolved fluoroimmunoassay based on the use of external luminescence modulators.

Influence of bulky N-substituents on the formation of lanthanide triple helical complexes with a ligand derived from bis(benzimidazole)pyridine: structural and thermodynamic evidence.

The planar aromatic tridentate ligand 2,6-bis(1-S-neopentylbenzimidazol-2-yl)pyridine (L(11)) reacts with Ln(III) (Ln = La-Lu) in acetonitrile to give the successive complexes [Ln(L(11))(n)](3+) (n = 1-3). However, stability constants determined by spectrophotometry and NMR titrations show that formation of the tris complexes is not favored, log K(3) being around 1 for La(III) and Eu(III), while no such species could be evidenced for the smaller Lu(III) ion. The X-ray structures of L(11) (monoclinic, P2(1), a = 13.4850(12) A, b = 12.0243(11) A, c = 16.4239(14) A, beta = 103.747(7) degrees ), [La(ClO(4))(2)(L(11))(2)](3)[La(ClO(4))(2)(H(2)O)(L(11))(2)](ClO(4))(4).15MeCN (1a, monoclinic, P2(1), a = 21.765(4) A, b = 30.769(6) A, c = 21.541(5) A, beta = 116.01(3) degrees ), and [Eu(L(11))(3)](ClO(4))(3).4.28MeCN (5a, monoclinic, P1, a = 14.166(3) A, b = 19.212(4) A, c = 21.099(4) A, alpha = 108.91(3) degrees, beta = 98.22(3) degrees, gamma = 108.40(3) degrees ) have been solved. In 1a, two different types of complex cations are evidenced, both containing 10-coordinate La(III) ions. In the first type, both perchlorate anions are bidentate, while in the second type, one perchlorate is monodentate, the 10th coordination position being occupied by a water molecule. In 5a the three ligands are not equivalent. Ligands A and B are wrapped in a helical way and are mirror images of each other, while ligand C lies almost perpendicular to the two other ones. This stems from the steric hindrance generated by the bulky neopentyl groups with the consecutive loss of any stabilizing interstrand pi-stacking interactions. This explains the low stability of the tris complexes and the difficulty of isolating them and points to the importance of the steric factors in the design of self-assembled triple helical lanthanide-containing functional edifices [Ln(L(i))(3)](3+).

A combined parallel synthesis and screening of macrocyclic lanthanide complexes for the cleavage of phospho di- and triesters and double-stranded DNA.

A parallel synthesis of macrocyclic lanthanide-ligand complexes 4Ln has been developed in conjunction with a parallel screening of these ligands for catalysis of phosphate ester hydrolysis. Complexes 4Ln were screened on a 96-well plate reader for their ability to catalyze the hydrolysis of a variety of phosphate esters efficiently. The hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) 5 and p-nitrophenylethyl phosphate 6 was accelerated by up to 150-fold in the presence of the complex 4cGd. The cleavage of a double-stranded DNA plasmid with this same complex obeyed saturation kinetics following a Michaelian model (K(m) = 7.4 microM, kcat = 4.5 x 10(-3) min-1). Our findings demonstrate how a combination of parallel synthesis and screening can expedite compound access, accelerate catalyst identification, and thereby dramatically increase the speed of finding good ligand-metal combinations.