Thulium doped monoclinic KLu(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> single crystals: growth and spectroscopy

This paper presents the crystal growth and optical characterization of thulium-doped KLu(WO₄)₂ (KLuW). Thulium-doped KLuW macrodefect-free monoclinic single crystals (a^*×b×c≈10×7×15 mm³) were grown by the top seeded solution growth slow cooling method with dopant concentrations of 0.5%, 1%, 3% and 5% atomic in solution. The evolution of unit cell parameters in relation with thulium doping was studied by X-ray powder patterns. Thulium energy levels in the KLuW host were determined by 6 K polarized optical absorption. The Judd–Ofelt parameters determined were Ω₂=9.01×10^-20 cm², Ω₄=1.36×10^-20 cm² and Ω₆=1.43×10^-20 cm². The maximum emission cross section for the 1.9 μm emission, calculated by Füchtbauer–Ladenburg method, is 1.75×10^-20 cm², at 1845 nm with E//N_m. The intensity decay time from the emitting levels ¹ G ₄ and ³ H ₄ levels in relation to the concentration were studied. For the lowest thulium concentration, the measured decay times from ¹ G ₄ and ³ H ₄ emitting levels are 140 μs and 230 μs, respectively. PACS 42.55.Rz; 78.20.-e; 78.55.-m     

The first enantioselective synthesis of 4-acetyl-3(R)- and 3(S)-(hydroxymethyl)-3,4-dihydro-2H-pyrido[3,2-b]oxazine

A novel short and enantioselective synthetic approach to pyridobenzoxazines is reported in which (R)- and (S)-3-(hydroxymethyl)-3,4-dihydro-2H-pyrido[3,2-b][1,4]oxazine were first synthesized from readily available chiral glycidyl derivatives.     

Syntheis of 2-aryloxy- and 2-arylalkoxy-1-(2-piperidyl)ethanols

The preparation and separation of diastereomeric pairs of a series of 2-aryloxy- and 2-arylalkoxy-1-(2-piperidyl)ethanols is reported. The erythro aminoalcohols were converted into threo isomers by thionyl chloride treatment of their N-acetyl derivatives and alkaline hydrolysis.     

Configurational and conformational aspects of some 5-methylenedisubstituted-3-pyrrolin-2-ones

The influence of the disubstitution at the exocyclic carbon atom of 5-methylene-3-pyrrolin-2-ones upon the configurational and conformational equilibria is studied. The results obtained confirm and extend the observations reported in the literature about the factors determining the configurational and conformational equilibria in monosubstituted systems, i.e.: 5-arylmethylene-3—pyrrolin-2-ones and 5(1H)-pyrromethenones.

---

Zur Konfiguration und Konformation von einigen 5-Methylen-disubstituierten-3-pyrrolin-2-onen

Zusammenfassung Es wird der Einfluß der Disubstitution des exocyclischen C-Atoms von 5-Methylen-3-pyrrolin-2-onen auf das Konfigurations- und Konformationsgleich-gewicht untersucht. Die erhaltenen Resultate stehen im Einklang mit der Literatur, die sich auf monosubstituierte Verbindungen [5-Arylmethylen-3-pyrrolin-2-one, 5 (1H)-Pyrromethenone und strukturverwandte Gallenpigmente] beziehen, und vertiefen das Verständnis der Faktoren, die für diese Gleichgewichte maßgebend sind.