A Dy(III) Fluorescent Single-Molecule Magnet Based on a Rhodamine 6G Ligand

The complexes of lanthanide metals, especially dysprosium, can generally exhibit excellent magnetic properties. By means of modifying ligands, dual functions or even multi-functions can be achieved. Here, we synthesized an eight-coordinate Dy(III) complex 1, [Dy(HL-o)2(MeOH)2](ClO4)3·4.5MeOH, which is single-molecule magnet (SMM), and the introduction of the rhodamine 6G chromophore in the ring-opened ligand HL-o realizes ligand-centered fluorescence in addition to SMM. Magnetic measurements and ab initio calculations indicate that the magnetic relaxation for complex 1 should be due to the Raman relaxation process. Studies on magneto-structural correlationship of the rhodamine salicylaldehyde hydrazone Dy(III) complexes show that the calculated energy of the first Kramers Doublet (EKD1) is basically related to the Ophenoxy-Dy-Ophenoxy bond angle, i.e., the larger Ophenoxy-Dy-Ophenoxy bond angle corresponds to a larger EKD1.

Effect of the Addition of Alkaline Earth and Lanthanide Metals for the Modification of the Alumina Support in Ni and Ru Catalysts in CO2 Methanation

In order to reduce greenhouse gas emissions, which are reaching alarming levels in the atmosphere, capture, recovery, and transformation of carbon dioxide emitted to methane is considered a potentially profitable process. This transformation, known as methanation, is a catalytic reaction that mainly uses catalysts based on noble metals such as Ru and, although with less efficiency, on transition metals such as Ni. In order to improve the efficiency of these conventional catalysts, the effect of adding alkaline earth metals (Ba, Ca, or Mg at 10 wt%) and lanthanides (La or Ce at 14 wt%) to nickel (13 wt%), ruthenium (1 wt%), or both-based catalysts has been studied at temperatures between 498 and 773 K and 10 bar pressure. The deactivation resistance in presence of H2S was also monitored. The incorporation of La into the catalyst produces interactions between active metal Ni, Ru, or Ru-Ni and the alumina support, as determined by the characterization. This fact results in an improvement in the catalytic activity of the 13Ni/Al2O3 catalyst, which achieves a methane yield of 82% at 680 K for 13Ni/14La-Al2O3, in addition to an increase in H2S deactivation resistance. Furthermore, 89% was achieved for 1Ru-13Ni/14La-Al2O3 at 651 K, but it showed to be more vulnerable to H2S presence.

ELECTRON WORK FUNCTION OF LANTHANIDE TRIIODIDES

Desorption enthalpies of LnI4– and Ln2I7– associative ions (Ln = La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, and Lu) and the enthalpy of sublimation of LnI3 molecules were determined by Knudsen effusion mass spectrometric technique. These data were used to calculate the effective values of electron work function φe of polycrystalline samples of lanthanide triiodides LnI3 for the first time. The calculation methodology is based on the study of thermochemical cycles, which include atoms, molecules, ions, and electrons being in thermodynamic equilibrium with the LnI3 crystal inside the effusion cell. The values obtained for different lanthanides turned out to be close. They lie in the range of about 2.4 – 4.4 eV with an average value in the series: φe = 3.2 ± 0.3 eV. The latter value is close to those for previously studied lanthanide tribromides. No secondary periodicity of φe was found within the calculated errors along the lanthanide series. The results obtained are in quantitative agreement with the theoretical calculation of the values of the band gap of lanthanide triiodides. Comparison of φe with other classes of lanthanide compounds such as oxides, hexaborides, and lanthanide metals shows relatively high electron emission ability yielding only to alkali and alkali-earth metals.

Facile dissociation of molecular nitrogen using lanthanide surfaces: towards ambient temperature ammonia synthesis

A combined experimental and computational study is reported on a hitherto unrecognised single lanthanide catalyst for the breaking of molecular nitrogen and formation of ammonia at ambient temperature and low pressure.<br>We combine in situ electrical conductance and electron diffraction measurements to track the conversion from the lanthanide metals to the insulating lanthanide nitrides.<br>The efficiency of the conversion is then interpreted using DFT+U calculations, suggesting a molecular nitrogen dissociation pathway separate from that well-established for transition metals.<br>Finally, we show that exposure of the lanthanide surfaces to both molecular nitrogen and hydrogen results in the formation of ammonia.<br><br>

Facile dissociation of molecular nitrogen using lanthanide surfaces: towards ambient temperature ammonia synthesis

A combined experimental and computational study is reported on a hitherto unrecognised single lanthanide catalyst for the breaking of molecular nitrogen and formation of ammonia at ambient temperature and low pressure.<br>We combine in situ electrical conductance and electron diffraction measurements to track the conversion from the lanthanide metals to the insulating lanthanide nitrides.<br>The efficiency of the conversion is then interpreted using DFT+U calculations, suggesting a molecular nitrogen dissociation pathway separate from that well-established for transition metals.<br>Finally, we show that exposure of the lanthanide surfaces to both molecular nitrogen and hydrogen results in the formation of ammonia.<br><br>

A Mutagenic Screen Identifies a TonB-Dependent Receptor Required for the Lanthanide Metal Switch in the Type I Methanotroph “Methylotuvimicrobium buryatense” 5GB1C

ABSTRACTSeveral of the metabolic enzymes in methanotrophic bacteria rely on metals for both their expression and their catalysis. The MxaFI methanol dehydrogenase enzyme complex uses calcium as a cofactor to oxidize methanol, while the alternative methanol dehydrogenase XoxF uses lanthanide metals such as lanthanum and cerium for the same function. Lanthanide metals, abundant in the earth’s crust, strongly repress the transcription ofmxaFyet activate the transcription ofxoxF. This regulatory program, called the “lanthanide switch,” is central to methylotrophic metabolism, but only some of its components are known. To uncover additional components of the lanthanide switch, we developed a chemical mutagenesis system in the type I gammaproteobacterial methanotroph “Methylotuvimicrobium buryatense” 5GB1C and designed a selection system for mutants unable to repress themxaFpromoter in the presence of lanthanum. Whole-genome resequencing for multiple lanthanide switch mutants identified several unique point mutations in a single gene encoding a TonB-dependent receptor, which we have named LanA. The LanA TonB-dependent receptor is absolutely required for the lanthanide switch and controls the expression of a small set of genes. While mutation of thelanAgene does not affect the amount of cell-associated lanthanum, it is essential for growth in the absence of the MxaF methanol dehydrogenase, suggesting that LanA is involved in lanthanum uptake to supply the XoxF methanol dehydrogenase with its critical metal ion cofactor. The discovery of this novel component of the lanthanide regulatory system highlights the complexity of this circuit and suggests that further components are likely involved.IMPORTANCELanthanide metals, or rare earth elements, are abundant in nature and used heavily in technological devices. Biological interactions with lanthanides are just beginning to be unraveled. Until very recently, microbial mechanisms of lanthanide metal interaction and uptake were unknown. The TonB-dependent receptor LanA is the first lanthanum receptor identified in a methanotroph. Sequence homology searches with known metal transporters and regulators could not be used to identify LanA or other lanthanide metal switch components, and this method for mutagenesis and selection was required to identify the receptor. This work advances the knowledge of microbe-metal interactions in environmental niches that impact atmospheric methane levels and are thus relevant to climate change.

Hydrogenation Properties of LnAl2 (Ln = La, Eu, Yb), LaGa2, LaSi2 and the Crystal Structure of LaGa2H0.71(2)

Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and / or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like SrTr2H2 (Tr = Al, Ga) with slightly puckered honeycomb-like polyanions decorated with hydrogen atoms. This study addresses the hydrogenation behavior of LnTr2, where the lanthanide metals Ln introduce one additional valence electron. Hydrogenation reactions were performed in autoclaves and followed by thermal analysis up to 5.0 MPa hydrogen gas pressure. Products were analyzed by powder X-ray and neutron diffraction, transmission electron microscopy, and NMR spectroscopy. Phases LnAl2 (Ln = La, Eu, Yb) decompose into binary hydrides and aluminium-rich intermetallics upon hydrogenation, while LaGa2 forms a ternary hydride LaGa2H0.71(2). Hydrogen atoms are statistically distributed over two kinds of trigonal-bipyramidal La3Ga2 interstitials with 67% and 4% occupancy, respectively. Ga-H distances (2.4992(2) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. 2H solid-state NMR spectroscopy and theoretical calculations on Density Functional Theory (DFT) level confirm that LaGa2H0.7 is a typical interstitial metallic hydride.