Tunable white light emission from single-phased Li2 SrSiO4 :Dy(3+) phosphors by co-doping with Eu(3+).

A series of single-phase full-color emitting Li2 Sr1-x-y SiO4 :xDy(3+) ,yEu(3+) phosphors were synthesized by solid-state reaction and characterized by X-ray diffraction and photoluminescence analyses. The samples showed emission peaks at 488 nm (blue), 572 nm (yellow), 592 nm (orange) and 617 nm (red) under 393 nm excitation. The photoluminescence excitation spectra, comprising the Eu-O charge transfer band and 4f-4f transition bands of Dy(3+) and Eu(3+) , range from 200 to 500 nm. The Commission Internationale de I'Eclairage chromaticity coordinates for Li2 Sr0.98-x SiO4 :0.02Dy(3+) ,xEu(3+) phosphors were simulated. By manipulating Eu(3+) and Dy(3+) concentrations, the color points of Li2 Sr1-x-y SiO4 :xDy(3+) ,yEu(3+) were tuned from the greenish-white region to white light and eventually to reddish-white region, demonstrating that a tunable white light can be obtained by Li2 Sr1-x-y SiO4 :xDy(3+) ,yEu(3+) phosphors. Li2 Sr0.98-x SiO4 :0.02Dy(3+) , xEu(3+) can serve as a white-light-emitting phosphor for phosphor-converted light-emitting diode.

Self-Assembly and Nanostructures in Organogels Based on a Bolaform Cholesteryl Imide Compound with Conjugated Aromatic Spacer.

The self-assembly of small functional molecules into supramolecular structures is a powerful approach toward the development of new nanoscale materials and devices. As a class of self-assembled materials, low weight molecular organic gelators, organized in special nanoarchitectures through specific non-covalent interactions, has become one of the hot topics in soft matter research due to their scientific values and many potential applications. Here, a bolaform cholesteryl imide compound with conjugated aromatic spacer was designed and synthesized. The gelation behaviors in 23 solvents were investigated as efficient low-molecular-mass organic gelator. The experimental results indicated that the morphologies and assembly modes of as-formed organogels can be regulated by changing the kinds of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecule self-assemble into different aggregates, from wrinkle and belt to fiber with the change of solvents. Spectral studies indicated that there existed different H-bond formations between imide groups and assembly modes. Finally, some rational assembly modes in organogels were proposed and discussed. The present work may give some insight to the design and character of new organogelators and soft materials with special structures.

N'-(4-Diethyl-amino-2-hy-droxy-benzyl-idene)-4-methyl-benzohydrazide.

The title compound, C(19)H(23)N(3)O(2), was prepared by condensing 4-diethyl-amino-2-hy-droxy-benzaldehyde and 4-methyl-benzo-hydrazide in methanol. The asymmetric unit contains two independent mol-ecules in which the two benzene rings make dihedral angles of 30.3 (3) and 18.9 (3)°. Intra-molecular O-H⋯N hydrogen bonds are observed in both mol-ecules. The crystal structure is stabilized by N-H⋯O hydrogen bonds, which form chains along the a axis.

2-Hy-droxy-N'-(5-hy-droxy-2-nitro-benzyl-idene)-3-methyl-benzohydrazide.

The title compound, C(15)H(13)N(3)O(5), was prepared by condensing 5-hy-droxy-2-nitro-benzaldehyde and 2-hy-droxy-3-methyl-benzohydrazide in methanol. The two benzene rings make a dihedral angle of 3.9 (3)°. An intra-molecular O-H⋯O hydrogen bond is observed. The crystal structure is stabilized by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds, and C-H⋯O and π-π inter-actions [centroid-centroid distances = 3.5658 (17)-3.9287 (19) Å].

2-Hy-droxy-N'-(4-hy-droxy-benzyl-idene)-3-methyl-benzohydrazide.

The title compound, C(15)H(14)N(2)O(3), was prepared by condensing 4-hy-droxy-benzaldehyde and 2-hy-droxy-3-methyl-benzo-hydra-zide in methanol. The two benzene rings make a dihedral angle of 19.03 (11)°. An intra-molecular O-H⋯O hydrogen bond is observed. The crystal structure is stabilized by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds and C-H⋯O inter-actions, which lead to the formation of a three-dimensional network.

N'-(3-Eth-oxy-2-hy-droxy-benzyl-idene)-2-hy-droxy-3-methyl-benzohydrazide.

The title compound, C(17)H(18)N(2)O(4), crystallizes with two independent mol-ecules in the asymmetric unit. The two benzene rings in each mol-ecule make dihedral angles of 7.6 (3) and 3.9 (3)°. Intra-molecular O-H⋯N and O-H⋯O hydrogen bonds are present in each mol-ecule. In the crystal, N-H⋯O hydrogen bonds link the mol-ecules into chains propagating in [010]. The are also a number of C-H⋯O and π-π inter-actions present [centroid-centroid distances = 3.874 (4) and 3.904 (3) Å], that result in the formation of a three-dimensional network.

A second monoclinic polymorph of 4-(2-hydr-oxy-4-methoxy-benzyl-ideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one.

The title compound, C(19)H(19)N(3)O(3), prepared by condensing 4-amino-anti-pyrine and 4-meth-oxy-2-hydroxy-benzaldehyde in methanol, is the second monoclinic polymorph of this compound which crystallizes in the space group C2/c. The structure was previously reported [Wang, Zhang, Yan, Zheng & Yang (2007 ▶). Acta Cryst. E63, o1245-o1246] in the space group P2(1)/c. The hydroxyl group is disordered over two positions with occupancies of 0.787 (4) and 0.213 (4). The triply substituted benzene ring and the phenyl ring form dihedral angles of 12.2 (2) and 53.7 (2)°, respectively, with the pyrazolone ring; the corresponding values in the P2(1)/c polymorph are 7.5 (2) and 42.6 (2)°. Intra-molecular O-H⋯N and C-H⋯O hydrogen bonds are observed in the major disorder component. Adjacent molecules are linked through intermolecular O-H⋯O hydrogen bonds, forming dimers.