M. E. Burin

Lanthanide complexes with substituted naphtholate ligands: extraordinary bright near-infrared luminescence of ytterbium

A series of Pr, Nd, Ho, Er, Tm, and Yb complexes with 3-(2-benzoxazol-2-yl)-2-naphtholate and 3-(2-benzothiazol-2-yl)-2-naphtholate ligands was synthesized. The structure, as well as the photo- and electroluminescent properties of these complexes were studied. An extraordinary bright emission of Yb3+ was detected. To explain the phenomenon, a novel excitation mechanism involving intramolecular electron transfer was proposed.

Metathesis reactions of neodymium and dysprosium diiodide-hydrides with organopotassium compounds: structure of [K(THF)2][(η5-C5H5)3Nd(μ-H)Nd(η5-C5H5)3] and [K(THF)2][Nd3(PhO)10(THF)4]

Reaction of neodymium iodide-hydride NdI2H with CpK in THF affords organoneodymium hydride [K(THF)2][(η5-C5H5)3Nd(μ-H)Nd(η5-C5H5)3] (1). Dysprosium analog DyI2H under the same conditions yields the known complex Cp3Dy(THF). The reaction of NdI2H with potassium phenoxide in THF affords the ionic cluster [K(THF)2][Nd3(PhO)10(THF)4] (2). In each case, interaction is accompanied by dihydrogen evolution. The molecular structures of 1 and 2 have been defined by X-ray diffraction analysis. The interaction of NdI2H with CpNa or CpLi gives an intractable mixture of products. The compounds PhC≡CK, NaN(SiMe3)2, KN(SiMe3)2, K( ), and C5Me5K are inert toward NdI2H.

Substituted naphtholates of rare earth metals as emissive materials

The synthesis, characterization, photoluminescent (PL) and electroluminescent (EL) behavior of trivalent Sc, Nd, Gd, Er, Tm and Yb complexes with 3-(5-methylbenzoxazol-2-yl)naphthol (L-5Me) and 3-(6-methylbenzoxazol-2-yl)naphthol (L-6Me) ligands are reported. An X-ray analysis of Sc(L-5Me)3, Sc(L-6Me)3 as well as the non-methylated analogue Sc(L)3 has shown the monomeric structure of the complexes whereas the lanthanide naphtholates according to LDI-TOF data are dimers Ln2(L-5Me)6 and Ln2(L-6Me)6. The scandium complexes under photo- and electroexcitation revealed intense ligand-centered luminescence peaked at 522 nm. The PL and EL spectra of Nd, Tm and Yb compounds displayed moderate ligand-centered emission along with narrow bands of corresponding f–f transitions.

ate complexes of lanthanides with aryloxide ligands: Synthesis, structures, and luminescence properties

Abstract(2-Benzox(thi)azol-2-yl)phenolate and -naphtholate ate complexes of Sc, Y, La, Sm, Tb, and Yb are synthesized. The structure of (benzoxazolyl)phenolate complexes of La, Sm, and Yb are determined by X-ray diffraction analysis. All synthesized compounds manifest ligand-centered photo- and electroluminescence in a range of 510–540 nm. In addition, the spectra of the samarium and terbium complexes exhibit narrow bands of f-f transitions characteristic of Sm3+ and Tb3+ ions.

Synthesis of EuS and EuSe particles via thermal decomposition of dithio- and diselenophosphinate europium complexes

New two- and trivalent europium complexes with dithio- and diselenodiphenylphosphinate ligands (S2PPh2- and Se2PPh2-) have been synthesized as precursors for nanoparticles. Two-valent europium compounds have been characterized via X-ray diffraction. Their photoluminescence properties have been studied as well. EuS colloidal nanoparticles have been obtained via the thermolysis of Eu(S2PPh2)n (n = 2, 3) in a hexadecylamine medium at 310°C. The average size of objects is found to be 40–70 nm. As is established, the valent state of a lanthanide in the complex exerts no influence on the size of the forming nanoparticles or on the luminescence spectrum of colloidal solutions.

Synthesis, quantum chemical calculations, and luminescent properties of scandium, europium, gadolinium, and terbium 1-(2-pyridyl)naphtholate complexes

By reactions of 1-(2-pyridyl)naphth-2-ol (pynH) with silylamides Ln[N(SiMe3)2]3 (Ln = Sc, Eu, Gd, or Tb), the Ln(pyn)3 complexes of the metals have been synthesized. Only the scandium complex in a THF solution has displayed photoluminescence (band with a maximum at 455 nm and a halfwidth of 65 nm). Electroluminescent properties have been revealed for the scandium and terbium complexes. In an ITO/TPD/Sc(pyn)3/Bath/Yb three-layer light emitting diode, the scandium complex exhibits yellow-green luminescence with a brightness of 4750 cd/m2 at a voltage of 21 V. The terbium complex Tb(pyn)3 in the same device has displayed a single, broad luminescence band with λmax = 570 nm due to excimer emission. By density functional theory quantum chemical calculations, different structures of the complexes have been revealed, mononuclear for Sc(pyn)3 and binuclear for Ln2(pyn)6. This difference in structure seems to be responsible for differences in electroluminescent activity between the synthesized complexes.

Features of spectral properties of Sm3 + complexes with dithia- and diselenophosphinate ligands

The samarium complexes Sm(S2PPh2)3(THF)2 (1) and Sm(Se2PPh2)3(THF)2 (2) with soft-donor dithia- and diselenophosphinate ligands were synthesized and their photophysical properties were studied in detail. Both complexes displayed the metal-centered photoluminescence (PL) in visible and NIR regions corresponding to (4)G5/2→(6)HJ (J=5/2, 7/2, 9/2, 11/2, 13/2, 15/2), (6)FJ (J=1/2, 3/2, 5/2, 7/2, 9/2, 11/2) f-f transitions of Sm(3+). Luminescence decay curves exhibit an initial short build-up region and can be described by double or triple exponential function owing to multiphonon relaxation from the (4)F3/2 energy level to the (4)G5/2 one and reversible energy transfer from the Sm(3+) excited states to the triplet ((3)T1) state of phosphinate ligand. A Judd-Ofelt analysis was performed to estimate PL quantum efficiency (QE), branching ratios (β) and induced-emission cross section (σem) of the compounds obtained. It was found that the Judd-Ofelt parameter Ω2 of 1 is significantly greater than that of 2. This feature is responsible for large values of β (50.98%) and σem (4.29×10(-21)cm(2)) which suggest 1 as a good candidate for the development of samarium doped polymethylmethacrylate (PMMA) laser medium acting on the (4)G5/2→(6)H9/2 transition at 645nm. The estimated room-temperature PL QE of 1 and 2 equals to 1.9 and 0.17%, respectively.