Rare earths: jewels for functional materials of the future

In recent decades, rare earths have become vital to a wealth of advanced materials and technologies including catalysts, alloys, magnets, optics and lasers, rechargeable hydride batteries, electronics, economical lighting, wind- and solar-energy conversion, bio-analyses and imaging. In this perspective article we give a broad overview of rare earth resources and uses first and then of selected applications in dedicated fields such as telecommunications, lasers, photovoltaics (solar-energy conversion), lighting (fluorescent lamps and OLEDs), luminescent probes for bio-analyses and bio-imaging, as well as magnetism and magnetic refrigeration. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

A Unique LnIII{[3.3.1]GaIII Metallacryptate} Series That Possesses Properties of Slow Magnetic Relaxation and Visible/Near‐Infrared Luminescence

A new family of [3.3.1] metallacryptates with the general composition [LnGa6(H2shi)(Hshi)(shi)7(C5H5N)] (Ln‐1; shi3−=salicylhydroximate; Ln = Pr, Nd, Sm–Yb) has been synthesized and characterized. Ln‐1 display both interesting magnetic and luminescent properties. Sm‐1 has sharp emission bands in the visible and the near‐infrared (NIR) regions with quantum yield values (QSmL) of 1.64(9) and 5.5(2).10−2 %, respectively. Tb‐1 exhibits a weak green emission (QTbL=1.89(3).10−1 %) while Pr‐1, Nd‐1, Ho‐1, Er‐1, and Yb‐1 possess emission bands in the NIR range with QPrL=3.7(2).10−3 %, QNdL=1.71(5).10−1 %, QHoL=1.1(2).10−3 %, QErL=7.1(2).10−3 % and QYbL=0.65(3) %. Nd‐1, Dy‐1, and Yb‐1 display slow magnetization relaxation in an applied field, where only Dy‐1 has been observed to follow an Orbach process (Ueff=12.7 K). The combination of NIR emission with magnetic properties makes Nd‐1 and Yb‐1 attractive candidates as smart materials addressable in two manners.A two‐for‐one scaffold: A new LnIII‐encapsulating metallamacrocyclic scaffold was synthesized and structurally determined to resemble cryptands. This metallacryptand can bind a wide variety of LnIII ions of different natures and demonstrates the ability to sensitize their characteristic emissions in the visible and/or near‐infrared. Slow magnetic relaxation was also observed for selected LnIII.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145255/1/chem201801355.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145255/2/chem201801355_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145255/3/chem201801355-sup-0001-misc_information.pd

Self-assembly of a helical zinc-europium complex: speciation in aqueous solution and luminescence

International audienceTwo new tridentate(NNO)-bidentate(NN) compartmental ligands, HL5 and HL6, are synthesized from pyridine and benzimidazole synthons. They react in aqueous solution under physiological conditions with ZnII, LnIII, or a mixture thereof, to yield complexes of different stoichiometries, 1:3, 2:2, 2:3, 1:1:3, the speciation of which is established by UV-visible titrations and ESI mass spectrometry. Photophysical studies of the EuIII-containing solutions in Tris-HCl 0.1 M (pH = 7.4) show that lanthanide luminescence arises from a unique N6O3 coordination site with pseudo D3 symmetry. Relevant parameters such as crystal field splitting, lifetime, radiative lifetime, and intrinsic quantum yield perfectly match those reported for dinuclear 4f-4f helicates in which the EuIII ion has the same coordination environment

The luminescence of NaxEu3+(2−x)/3MoO4 scheelites depends on the number of Eu-clusters occurring in their incommensurately modulated structure

Scheelite related compounds with general formula Mn(XO4)m are of interest owing to their optical properties, stability and relatively simple preparation. Eu3+-containing scheelites are considered as red emitting phosphors and the main factors affecting their luminescence are thought to be chemical composition and particle size while the influence of their structure is generally ignored. Here we report eight compounds from the NaxEu(2_x)/3MoO4 series prepared by conventional solid-state reaction and present a detailed analysis of their crystal structures. Six of them have modulated structures, a common feature of SRCs, in which dopant Eu3+ ions are orderly distributed. Moreover, different amounts of Eu3+ dimers are detected in the modulated structures, characterized by weak satellite reflections appearing in the lower angle part of the XRD patterns. These reflections are indexed and incorporated into Rietveld’s refinement using superspace (3 + 1)-dimension symmetry. The remarkable feature of the compounds is that the characteristic luminescence parameters, overall and intrinsic quantum yields, Eu lifetimes, and sensitization efficiencies, correlate with the number of Eu3+ aggregates, but not directly with the composition x of the materials. This provides an efficient tool for understanding and controlling the luminescence properties of scheelite related compounds

Vanadium oxide - poly(3,4-ethylenedioxythiophene) cathodes for zinc-ion batteries: effect of synthesis temperature

Vanadium oxide composites with conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) were obtained by one-step microwave-assisted hydrothermal synthesis at two different temperatures: 120 and 170 °C (denoted as V-120 and V-170, respectively). The structure and composition of the obtained samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectro­scopy (XPS), and thermogravimetric (TG) analysis. The detailed study of the electro­chemical properties of the composites as cathodes of aqueous zinc-ion battery was per­formed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) at different current densities and by electrochemical impedance spectroscopy (EIS). It was shown that V-120 demonstrated excellent electrochemical performance in the 0.3 to 1.4 V vs. Zn/Zn2+ potential range reaching specific capacities of up to 390 mA∙h∙g−1 at 0.3 A∙g−1 with excel­lent capacity stability after 1000 charge-discharge cycles. Its functional parameters were found to be much better than those of the electrodes based on the V-170 composite obtained at a higher temperature. The effect of the synthesis temperature on the electro­chemical properties is discussed in terms of the crystallographic, compositional, and thermogravimetric properties of the samples

Deciphering Three Beneficial Effects of 2,2 '-Bipyridine-N,N '-Dioxide on the Luminescence Sensitization of Lanthanide(III) Hexafluoroacetylacetonate Ternary Complexes

Lanthanide hexafluoroacetylacetonate ternary complexes with 2,2'-bipyridine-N,N'-dioxide, [Ln(hfa)3(bpyO2)], were synthesized for Ln = Eu, Gd, Tb, and Lu and fully characterized by elemental, thermal, and mass-spectrometric analyses. The X-ray crystal structure of [Eu(hfa) 3(bpyO2)].0.5C6H6 reveals an octa-coordinate metal ion lying in a severely distorted trigonal dodecahedron geometry; the Eu-O distances lie in the range 2.36-2.44 Å with no significant difference between hfa- and bpyO2. A detailed comparative photophysical investigation has been carried out to determine the exact influence of the introduction of bpyO2 in the inner coordination sphere of the metal ion in replacement of the two water molecules in [Ln(hfa)3(H2O)2]. While this replacement is detrimental for Tb, it leads to a 15-fold increase in the overall quantum yield for Eu. This large improvement originates from (i) a better sensitization efficiency, the ancillary ligand being responsible for 3/4 of the energy transfer, (ii) elimination of nonradiative deactivation pathways through harmonics of O-H vibrations, and (iii) reduction in the radiative lifetime. The latter influence is rarely documented, but it accounts here for ã25% increase in the intrinsic quantum yield, so that more attention should be given to this parameter when designing highly luminescent lanthanide complexes. © 2011 American Chemical Society

Unravelling the mechanism of water sensing by the Mg2+ dihydroxy-terephthalate MOF (AEMOF-1 ‘)

In this contribution we build upon our previous work on the MOF [Mg(H(2)dhtp)(H2O)(2)]center dot DMAc (AEMOF-1 center dot DMAc) and its activated dry version AEMOF-1 ‘ which has been shown to exhibit excellent luminescence sensing properties towards water in organic solvents. We demonstrate through combined structural and photophysical studies that the observed changes in the fluorescence properties of AEMOF-1 ‘ upon hydration arise from a structural transformation to the mononuclear complex [Mg(H(2)dhtp)(H2O)(5)]center dot H2O (H(4)dhtp = 2,5-dihydroxyterepthalic acid) (1). In the latter complex, excited state intramolecular proton transfer (ESIPT) is strongly favoured thereby leading to enhanced and red shifted emission in comparison to AEMOF-1 center dot DMAc. Powder X-ray diffraction measurements confirmed that complex 1 is identical to the hydrated form of AEMOF-1 center dot DMAc. As in the case of AEMOF-1 ‘, the dry form of complex 1 (1 ‘) is also an effective sensor for the determination of traces of water in tetrahydrofuran (THF). This work demonstrates that the same chromophore may exhibit very different emission properties when it exists in different chemical environments and that these transformations may be controlled and utilized in water sensing applications

Multiphoton-Excited Luminescent Lanthanide Bioprobes: Two- and Three-Photon Cross Sections of Dipicolinate Derivatives and Binuclear Helicates

Multiphoton excited luminescent properties of water-soluble EuIII and TbIII complexes with derivatives of dipicolinic acid functionalized with a polyoxyethylene pendant arm and terminal groups, [Eu(LOMe)3]3-, [Eu(LNH2)3]3-, and [Tb(LOH)3]3-, as well as of binuclear helicates with overall composition [Ln2(LCX)3] (X ) 2, 5) are investigated. Characteristic emission from the 5D0 and 5D4 excited levels of EuIII and TbIII, respectively, upon ≈800 nm excitation results from three-photon absorption (3PA) for [Eu(LOMe)3]3-, [Eu(LNH2)3]3-, [Tb(LOH)3]3-, and [Ln2(LC2)3], while luminescence from [Eu2(LC5)3] is induced by two-photon absorption (2PA) owing to its 1PA spectrum extending further into the visible. The 3PA cross sections have been determined and are the first ones reported for lanthanide complexes: (i) those of EuIII and TbIII bimetallic helicates [Ln2(LC2)3] are 20 times larger compared to the corresponding values for tris(dipicolinates); (ii) derivatization of dipicolinic acid for TbIII complexes has almost no influence on the 3PA cross section; however, for EuIII complexes a ∼2 times decrease is observed. The feasibility of [Eu2(LC5)3] as multiphoton luminescence bioprobe is demonstrated by two-photon scanning microscopy imaging experiments on HeLa cells incubated with this bimetallic helicate