Table 1. Existent Eu 2+ Nanophosphors, Size, and Emission Maximum (λ em ) for Nano and Bulk Phosphors compound size (nm) a λ em nano (nm) λ em bulk (nm) compound size (nm) a λ em nano (nm) λ em bulk (nm) aluminates

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The delicate dependence of the photoluminescence properties of Eu2+ on the structure of the perovskite-analogue iodides CsMI3 (M = Mg, Ca, Sr) is discussed.

Vibronic structure in the S 1 T S 0 absorption and fluorescence spectra of jet-cooled 1-naphthol is reexamined. Selective excitation of bands 410 or 414 cm -1 above the S 1 ( 1 L b ) origin leads to atypical, highly structured fluorescence, indicating that strong vibrational mixing occurs. From the intensity patterns and the appearance of otherwise dark modes, a large normal coordinate (Duschinsky) rotation is inferred. Vibronic coupling with the second electronic excited state ( 1 L a ) is proposed as the cause of the rotation, as supported by absorption/ emission mirror asymmetry, rotationally resolved spectra, and calculations. Coupled molecular dynamics and semiempirical simulations suggest that this vibronic coupling plays a major role in the solvent-controlled excited state proton transfer of naphthol in water by increasing the solvent-solute interaction. With vibronic mixing, L a /L b state inversion is predicted correctly as a result of coupled evolution of the solvent and solute. The excited naphthol charge distribution and the orientation of nearby water molecules change together, leading to large naphthol dipole moments. The model results are supported by the relevant data on 1-naphthol in water and water clusters.

Yellow Eu2+-doped strontium carbodiimide, SrNCN:Eu2+, adopting the α-SrNCN structure type was obtained by the reaction of SrI2, EuI2, CsN3 and CsCN in arc-welded Ta ampules. The product was characterized by high-resolution X-ray powder diffraction and infrared spectroscopy. Even at room temperature α-SrNCN:Eu2+ shows a strong orange emission peaking at 603 nm which is excitable by energies below 25 000 cm−1. The little change of the optical properties with increasing temperature is rather unexpected and leads to the assumption that this material is a promising candidate for future phosphor converted LEDs as well as a key compound for the understanding of the influence of the host lattice on the luminescence properties of Eu2+-doped materials.

The superbulky deca-aryleuropocene [Eu(Cp(BIG))2], Cp(BIG) = (4-nBu-C6H4)5-cyclopentadienyl, was prepared by reaction of [Eu(dmat)2(thf)2], DMAT = 2-Me2N-α-Me3Si-benzyl, with two equivalents of Cp(BIG)H. Recrystallizyation from cold hexane gave the product with a surprisingly bright and efficient orange emission (45% quantum yield). The crystal structure is isomorphic to those of [M(Cp(BIG))2] (M = Sm, Yb, Ca, Ba) and shows the typical distortions that arise from Cp(BIG)⋅⋅⋅Cp(BIG) attraction as well as excessively large displacement parameter for the heavy Eu atom (U(eq) = 0.075). In order to gain information on the true oxidation state of the central metal in superbulky metallocenes [M(Cp(BIG))2] (M = Sm, Eu, Yb), several physical analyses have been applied. Temperature-dependent magnetic susceptibility data of [Yb(Cp(BIG))2] show diamagnetism, indicating stable divalent ytterbium. Temperature-dependent (151)Eu Mössbauer effect spectroscopic examination of [Eu(Cp(BIG))2] was examined over the temperature range 93-215 K and the hyperfine and dynamical properties of the Eu(II) species are discussed in detail. The mean square amplitude of vibration of the Eu atom as a function of temperature was determined and compared to the value extracted from the single-crystal X-ray data at 203 K. The large difference in these two values was ascribed to the presence of static disorder and/or the presence of low-frequency torsional and librational modes in [Eu(Cp(BIG))2]. X-ray absorbance near edge spectroscopy (XANES) showed that all three [Ln(Cp(BIG))2] (Ln = Sm, Eu, Yb) compounds are divalent. The XANES white-line spectra are at 8.3, 7.3, and 7.8 eV, for Sm, Eu, and Yb, respectively, lower than the Ln2O3 standards. No XANES temperature dependence was found from room temperature to 100 K. XANES also showed that the [Ln(Cp(BIG))2] complexes had less trivalent impurity than a [EuI2(thf)x] standard. The complex [Eu(Cp(BIG))2] shows already at room temperature strong orange photoluminescence (quantum yield: 45 %): excitation at 412 nm (24,270 cm(-1)) gives a symmetrical single band in the emission spectrum at 606 nm (νmax =16495 cm(-1), FWHM: 2090 cm(-1), Stokes-shift: 2140 cm(-1)), which is assigned to a 4f(6)5d(1) → 4f(7) transition of Eu(II). These remarkable values compare well to those for Eu(II)-doped ionic host lattices and are likely caused by the rigidity of the [Eu(Cp(BIG))2] complex. Sharp emission signals, typical for Eu(III), are not visible.

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