Strong erbium luminescence in the near-infrared telecommunication window

A new type of near-infrared emitting rare-earth complex has been synthesised, consisting of three bis(perfluoroalkylsulfonyl)imide ligands and one 1,10-phenanthroline molecule. The chelate rings formed by the rare-earth ion and the bidentate ligands do not contain any carbon atoms and can hence be considered as 'inorganic' chelate rings. The absence of C-H stretching vibration modes in the first coordination sphere of the rare-earth ion and the presence of a light-harvesting moiety (1,10-phenanthroline) bound to the rare-earth ion result in a complex that can be efficiently excited and exhibits intense near-infrared luminescence.status: publishe

Spectroscopic properties of trivalent samarium ions in glasses

Optical absorption and luminescence spectra of the Sm3+-doped fluorophosphate glasses 75NaPO(3)-24CaF(2)-1SmF(3) and 75NaPO(3)-24BaF(2)-1 SmF3, the phosphate glass 75NaPO(3)-24.5ZnO-0.5Sm(2)O(3) and the fluoride glass ZBLAN:Sm3+ have been recorded. The dipole strengths of the transitions in the absorption spectrum are parameterized in terms of three phenomenological Judd-Ofelt intensity parameters Omega(lambda) (lambda = 2, 4 and 6). The determination of intensity parameters for Sm3+ has inherent difficulties due to very large number of energy levels lying close to each other. In this case, we can take advantage of the property that both the dipole strengths and the squared reduced matrix elements of overlapping transitions are additive. The relation between the spectral intensities and the glass composition is discussed

Speciation of uranyl nitrato complexes in acetonitrile and in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Complex formation between the uranyl ion and nitrate ions in acetonitrile and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]) has been studied by absorption, magnetic circular dichroism (MCD) and uranium LIII EXAFS spectroscopy. The experimental results point to the existence of a trinitrate species [UO2(NO3)3]- with D3h symmetry in both solvents. The atomic distances in the uranium(VI) coordination sphere for the trinitrato complex in acetonitrile are U-Oax = 1.77 ± 0.01 Å and U-Oeq = 2.48 ± 0.01 Å. EXAFS data show that the uranyl ion in the ionic liquid is surrounded by six oxygen atoms in the equatorial plane at a distance of 2.49 ± 0.01 Å. The U-N distance of 2.92 ± 0.01 Å indicates a bidentate coordination of the nitrate group in both solvents. A structural comparison is made between the uranyl trinitrato complex anion [UO2(NO3)3]- and the uranyl tricarbonato complex anion [UO2(CO3)3]4-. No evidence is found for the presence of uranyl nitrato complexes in aqueous solution. The optical absorption, MCD and EXAFS spectra resemble those of the hydrated free uranyl ion. There are two axial oxygen atoms at 1.77 ± 0.01 Å and five equatorial oxygen atoms at 2.41 ± 0.01 Å. These values agree well with structural parameters obtained for the uranyl aqua io

Mandelohydroxamic acid as ligand for copper(II) 15-metallacrown-5 lanthanide(III) and copper(II) 15-metallacrown-5 uranyl complexes

The formation of pentanuclear copper(II) complexes with the mandelohydroxamic ligand was studied in solution by electrospray ionization mass spectrometry (ESI-MS), absorption spectrophotometry, circular dichroism and H-1 NMR spectroscopy. The presence of lanthanide(III) or uranyl ions is essential for the self-assembly of the 15-metallacrown-5 compounds. The negative mode ESI-MS spectra of solutions containing copper(II), mandelohydroxamic acid and lanthanide(III) ions (Ln = La, Ce, Nd, Eu, Gd, Dy, Er, Tm, Lu, Y) or uranyl in the ratio 5:5:1 showed only the peaks that could be unambiguously assigned to the following intact molecular ions: {Ln(NO3)(2)[15-MCuIIN(MHA)-5](2-)}(-) and {Ln(NO3)[15-MCCuIIN(MHA)-5](3-)}(-), where MHA represents doubly deprotonated mandelohydroxamic acid. The NMR spectra of the pentanuclear species revealed only one set of peaks indicating a fivefold symmetry of the complex. The pentanuclear complexes synthesized with the enantiomerically pure R- or S-forms of mandelohydroxamic acid ligand, showed circular dichroism spectra which were mirror images of each other. The pentanuclear complex made from the racemic form of the ligand showed no signals in the CD spectrum. The UV/ Vis titration experiments revealed that the order in which the metal salts are added to the solution of the mandelohydroxamic acid ligand is crucial for the formation of metallacrown complexes. The addition of copper(II) to the solutions containing mandelohydroxamic acid and neodymium(III) in a 5:1 ratio lead to the formation of a pentanuclear complex in solution. In contrary, titration of lanthanide(III) salt to the solution containing copper(II) and mandelohydroxamic acid did not show any evidence for the formation of pentanuclear species.status: publishe

Visible and Near-Infrared Emission by Samarium(III)-Containing Ionic Liquid Mixtures

Highly luminescent anionic samarium(III) beta-diketonate and dipicolinate complexes were dissolved in the imidazolium ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(6)mim][Tf(2)N]. The solubility of the complexes in the ionic liquid was ensured by a careful choice of the countercation of the samarium(III) complex. The samarium(III) complexes that were considered are [C(6)mim][SM(tta)(4)], where tta is 2-thenoyltrifluoroacetonate; [C(6)mim][Sm(nta)(4)], where nta is 2-naphthoyltrifluoroacetonate; [C(6)mim][Sm(hfa)(4)], where hfa is hexafluoroacetylacetonate; and [choline](3)-[Sm(dpa)(3)], where dpa is pyridine-2,6-dicarboxylate (dipicolinate) and [choline](+) is (2-hydroxyethyl)trimethyl ammonium. The crystal structures of the tetrakis samarium(III) P-diketonate complexes revealed a distorted square antiprismatic coordination for the samarium(III) ion in all three cases. Luminescence spectra were recorded for the samarium(III) complexes dissolved in the imidazolium ionic liquid as well as in a conventional solvent, that is, acetonitrile or water for the beta-diketonate and dipicolinate complexes, respectively. These experiments demonstrate that [C(6)mim][Tf(2)N] is a suitable spectroscopic solvent for studying samarium(III) luminescence. High-luminescence quantum yields were observed for the samarium(III) beta-diketonate complexes in solution