Heterogeneous enantioselective epoxidation catalyzed by Mn(salen) complexes grafted onto mesoporous materials by phenoxy group

Three chiral Mn(salen) complexes were immobilized into different mesoporous material via phenoxy group by a simplified method and they show high activity and enantioselectivity for asymmetric epoxidation of various substituted unfunctional olefins. The heterogeneous Mn(salen) catalysts show comparable ee values for asymmetric epoxidation of styrene and 6-cyano-2,2-dimethylchromene and much higher ee values for epoxidation of a-methylstyrene (heterogeneous 79.7% ee versus homogeneous 26.4% ee) and cis-beta-methylstyrene (heterogeneous 94.9% ee versus homogeneous 25.3% ee for cis-epoxide) than the homogeneous catalysts. These heterogeneous catalysts also remarkably alter the cis/trans ratio of epoxides for asymmetric epoxidation of cis-beta-methylstyrene (heterogeneous 21 versus homogeneous 0.38). The axial tether group does not make a big effect on ee values and the increase in ee value and change in cis/trans ratio are mainly attributed to the axial immobilization mode and the support effect of heterogeneous catalysts. The catalysts keep constant ee values for the recycle tests of eight times for asymmetric epoxidation of a-methylstyrene. And several possibilities were proposed to elucidate the difference in ee values of heterogeneous catalysts from homogeneous catalysts. (c) 2005 Elsevier B.V. All rights reserved.

Post-grafting preparation of large-pore mesoporous materials with localized high content titanium doping

A new post-grafting process, consisting of two steps of substrate preparation and sol - gel post-grafting, has been developed to prepare titanium-doped mesoporous SBA-15 material with a double-layered structure and locally concentrated titanium content at the inner pore surface. With this novel technique, the single phased and originally ordered mesostructures can be well conserved; in the conventional direct synthesis they can be partially damaged when the frameworks are doped with high content heteroatoms. Titanium species exist in an isolated, tetrahedral structure and are localized at the pore surface; this is beneficial to both reactant access and product release. Characterization with XRD, N-2 adsorption/desorption isotherms, HREM/ EDS, ICP, UV - Vis, and the newly developed UV - Raman spectroscopy confirm these results. Preliminary catalytic tests with the selective epoxidation of cyclohexene show good catalytic activity. Among them, sample TiSBA-15-10 with a Si : Ti molar ratio of 10 shows a TON value of 75 and a highest product ( epoxide) yield of 55%.

钙钛矿型有机－无机杂化半导体材料的合成及其发光性质的研究

有机-无机钙钛矿型杂化半导体材料结合了有机和无机材料优点，并在分子水平上自组装形成复合材料，具有独特的光、电、磁等性质，在许多领域具有潜在的应用。基于第四主族金属卤化物的杂化钙钛矿是本论文研究的主题，这一类杂化钙钛矿材料是一类独特的半导体材料，其光功能引起人们越来越多的重视。 为此，本论文通过选择不同的有机阳离子配体制备了新型的基于卤化铅的有机－无机杂化钙钛矿结构单晶材料和薄膜，对它们的发光性质进行了研究。利用N-(3-胺基丙基)咪唑和溴化铅在氢溴酸溶液中反应得到了罕见的(110)取向杂化钙钛矿(C6H13N3)2PbBr4 (monoclinic, P21/c)。所得到的杂化钙钛矿在吸收(392 nm)及发射(424 nm)光谱中均存在激子的特征峰。同时，由于N-(3-胺基丙基)咪唑的光活性，得到的杂化材料具有独特的发光性质，在无机层与有机层之间发生了能量传递，使得有机配体的峰位发生红移并且发光强度明显增加。利用CASTEP (Cambridge Serial Total Energy Package) 总能计算软件包对配合物及配体的能带结构进行了计算。结果证明了配体在杂化材料中发光的红移及激子与配体间的能量传递。另外，还发现了一个有机配体2-(2-氨基乙基)硫脲也能够与金属卤化物络合形成(110)取向的有机－无机杂化钙钛矿结构C3H11SN3PbBr4(monoclinic P21/c)，由于有机配体的不同，2-(2-氨基乙基)硫脲构筑的(110)取向杂化钙钛矿结构较N-(3-胺基丙基)咪唑构筑的(110)取向杂化钙钛矿结构有较大程度的扭曲变形，使得它们的发光性质有所不同。 邻-(胺基甲基)吡啶，间-(胺基甲基)吡啶，对-(胺基甲基)吡啶在相同条件下与溴化铅组装，得到0-D [(m-C6H10N2)2PbBr6] (orthorhombic, Pbca), 1-D [(o-C6H10N2)PbBr4] (monoclinic, P21/c), 2-D [p-(C6H10N2)PbBr4] (orthorhombic, Pbca) 等不同维数的溴化铅骨架。其中间-(胺基甲基)吡啶与溴化铅在酸性条件下形成稀有的0-D杂化钙钛矿；邻-(胺基甲基)吡啶在相同条件下形成2-D层状杂化钙钛矿；对-(胺基甲基)吡啶则得到共边八面体组成的一维链。证实了有机配体氢键和空间位阻对无机结构的形成起限制作用。得到的杂化钙钛矿化合物的无机层激子特征吸收峰分别位于428 nm(0-D)和431 nm(1-D)，无机层激子特征发射峰位于461 nm (0-D)和467 nm(1-D)。 由于甲基咪盐的特殊胺盐构型，我们选用甲基咪盐取代的吡啶作为有机阳离子配体来构筑基于溴化铅的杂化钙钛矿，分别为3-甲咪基吡啶和4-甲咪基吡啶。3-甲咪基吡啶与溴化铅在酸性条件下构筑未见文献报道的即共点又共边的Pb-Br八面体连成无机层网络的杂化结构(C6H13N3)PbBr4 (monoclinic, C2/c)。4-甲咪基吡啶与溴化铅在相同条件下构筑的是常见的(100)取向的杂化钙钛矿结构(C6H13N3)PbBr4(orthorhombic, Pbca)。通过两个不同的化合物在结构和光学性质上的对比，表明有机阳离子配体对无机层结构以及杂化钙钛矿材料光学性质的影响。 在氢溴酸溶液中，组胺与卤化铅自组装成(100)取向杂化钙钛矿(C5H10N3)PbBr4 (monoclinic, P21/c)，(C5H10N3)PbCl4 (monoclinic, P21/c)。得到由扭曲的共角八面体组成的钙钛矿片层。受有机配体空间位阻及氢键的影响，无机层发生一定的扭曲，从而导致激子吸收较(分别位于419 nm，339 nm)线形脂肪胺有一定程度的红移。荧光光谱中存在基于溴化铅，氯化铅杂化钙钛矿激子的特征发射峰。另外作为比较，另一个复杂的有机胺3-氨基-1,2,4-三唑，在同样的条件下与PbBr2进行组装得到的是无机组分为一曲折的链状一维结构的杂化结构(C2H2N4)PbBr3 (orthorhombic, Pna21)。 线形的二咪唑配体2,2΄-(二咪唑基-甲基)苯和4,4΄-(二咪唑基-甲基)对联苯，由于其空间位阻与氢键的影响，与卤化铅的组装得到链状骨架。2,2΄-(二咪唑基-甲基)苯与氯化铅构筑的无机骨架是由共边铅氯三角锥连成的一维链状结构(C7H8N2)PbCl3 (triclinic, P-1)；与溴化铅形成类似交替排布的层状结构(C7H8N2)PbBr3 (triclinic, P-1)。4,4΄-(二咪唑基-甲基)对联苯构筑的氯化铅骨架为新奇的由共点的铅氯四方锥组成的类隧道形链(C20H21N4)Pb2Cl6•H2O (triclinic, P-1)；构筑的溴化铅骨架为由共边的铅溴八面体组成的双链(C20H21N4)Pb2Br6 (monoclinic, C2/c)。形成配合物的发光为配体本身的π-π*跃迁发光。 所合成的杂化钙钛矿材料都具有较好的成膜性，利用简单的旋涂法即可得到质量较好的薄膜材料，有利于对其进行光电研究。

White electroluminescence from a poly(N-vinylcarbazole) layer doped with CdSe/CdS core-shell quantum dots

Hybrid organic/inorganic white light-emitting diodes (LEDs) were fabricated of semiconductor polymer poly(N-vinylcarbazole) (PVK) doped with CdSe/CdS core-shell semiconductor quantum dots (QDs). The device, with a structure of indium-tin-oxide (ITO)vertical bar 3,4-polyethylene-dioxythiophene- polystyrene sulfonate (PEDOT:PSS)vertical bar PVK:CdSe/CdS vertical bar Al, emitted a pure white light spanning the whole visible region from 400 to 800 nm. The Commission Internationale del'Eclairage coordinates (CIE) remained at x = 0.33, y = 0.34 at wide applied voltages. The maximum brightness and electroluminescence (EL) efficiency reached 180 cd m(-2) at 19 V and 0.21 cd A(-1) at current density of 2 mA cm(-2), respectively. The realization of the pure white light emission is attributed to the incomplete energy and charge transfer from PVK to CdSe/CdS core-shell QDs.

Langmuir-Blodgett films based on europium-substituted heteropolytungstate and their luminescence properties

Several new hybrid organic-inorganic Langmuir-Blodgett (LB) films containing europium-substituted hetero-polytungstate Eu (XW11O39)(2)''(-) (X=Ge, Si, B) were successfully obtained using LB technique. When the heteropolytungstate anions are dissolved in the subphase, dimethyldioctadecylammonium bromide compression isotherms have been modified, which shows that the polyanions interact with the monolayer. Y-type LB films were obtained from the systems. Low-angle X-ray has shown that these LB films have well-defined lamella. The LB films were characterized by luminescence spectra and the characteristic luminescence behavior for europium-substituted heteropolytungstate complexes and their LB films were discussed. The results of excitation spectra indicate that the energy could be effectively transferred from ligands to the Eu3+ ions in the LB films and the luminescence efficiency could be greatly increased. The results of luminescence spectra indicate that the formations of hybrid organic-inorganic LB films have a great effect on the luminescence of europium-substituted heteropolytungstate. The lifetime shortening was observed in LB films.

Synthesis and Characterization of Urea Bridged Hybrid Periodic Mesoporous Organosilica Materials

Urea bridged organic-inorganic hybrid mesoporous SiO2 materials (U-BSQMs) were synthesized through a sol-gel procedure by co-condensation of bis(triethoxysilyl propyl) urea (BSPU) under basic conditions using cetyltrimethylammonium bromide (CTAB) as organic template. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the mesoporous structure of the sample. Fourier-transform infrared spectroscopy (FT-IR), solid state CP-MAS NMR spectroscopy of Si-29 (Si-29, CP-MAS NMR) and C-13 (C-13 CP NMR) indicated that most of the Si-C bonds are unbroken during the synthesis process.

Synthesis and spectroscopic study of mesoporous aluminum methylphosphonate foam templated by dibutyl methylphosphonate

New types of templates and novel interactive mechanisms between template and framework are very important for creating porous materials. In this work, by using neutral dibutyl methylphosphonate as a template, an inorganic-organic hybrid mesoporous material, aluminum methylphosphonate, was prepared. The as-synthesized material was studied by P-31 magnetic angle spinning nuclear magnetic resonance (MAS NMR), Al-27 MAS NMR, C-13 CP/MAS, FT-IR spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), and transmission electron microscopy. After thermal treatment at 673 K and 10 mmHg for 2 h, hybrid mesoporous foam was obtained. The transformation process was investigated by FT-IR. TG-DTA results indicate that the methyl group bonded to the framework keeps intact up to 792 K under air and 823 K under nitrogen. The characterization results from nitrogen gas adsorption-desorption measurements show that the BET surface area and the Barrett-Joyner-Halenda desorption cumulative pore volume of the foam are 90 m(2) g(-1) and 0.32 cm(3) g(-1) respectively. (C) 2003 Elsevier Inc. All rights reserved.

Novel hybrid periodic mesoporous organosilica material grafting with Tb complex: Synthesis, characterization and photoluminescence property

A novel periodic mesoporous organosilica (PMO) material was synthesized through one-step co-condensation of 1,2-bis(triethoxysilyl)ethane (BTESE) and benzoic acid-functionalized organosilane (BA-Si) using cetyltrimethylammonium bromide (CTAB) as a structure-directing agent under basic conditions. The materials were fully characterized by FTIR, XRD, N-2 adsorption-desorption isotherms and FESEM. FTIR spectra proved that BA-Si was successfully incorporated into the PMO materials (PMOs) via benzyl group as a linker. XRD and N-2 adsorption-desorption isotherms revealed the characteristic mesoporous structure with highly uniform pore size distributions. FESEM confirmed that the morphology of the PMOs was significantly dependent cri the molar ratio of two organosilica precursors.

A study on the near-infrared luminescent properties of xerogel materials doped with dysprosium complexes

A series of dysprosium complex doped xerogels with the same first ligand (acac = acetylacetone) and different neutral ligands were synthesized in situ via a sol-gel process. The Fourier transform infrared (FTIR) spectra, diffuse reflectance (DR) spectra, and near-infrared (NIR) luminescent properties of dysprosium complexes and dysprosium complex doped xerogels are described in detail. The results reveal that the dysprosium complex is successfully synthesized in situ in the corresponding xerogel. Excitation at the maximum absorption wavelength of the ligands resulted in the characteristic NIR luminescence of the Dy3+ ion, which contributes to the energy transfer from the ligands to the central Dy3+ ion in both the dysprosium complexes and xerogels via an antenna effect.

Construction and Photoluminescence of Monophase Hybrid Materials Derived from a Urea-Based Bis-Silylated Bipyridine

A urea-based bis-silylated bipyridine ligand derived from 4,4'-diamino-2,2'-bipyridine has been prepared. Organic-inorganic hybrid materials with a high loading of lanthanide 2,2-bipyridine moieties were obtained by using the silylated bipyridine as the only siloxane network precursor in the presence of lanthanide ions (or lanthanide complexes). The in-situ formation of lanthanide complexes from lanthanide ions and the silylated bipyridine during the sol-gel processing was confirmed by the luminescence behavior of the obtained hybrid materials and that of the corresponding pure lanthanide complex [Ln(bpy)(2)Cl-3 center dot 2H(2)O].

Novel Near-Infrared Luminescent Hybrid Materials Covalently Linking with Lanthanide [Nd(III), Er(III), Yb(III), and Sm(III)] Complexes via a Primary beta-Diketone Ligand: Synthesis and Photophysical Studies

A series of novel, colorless, and transparent sot-gel derived hybrid materials Ln-DBM-Si covalently grafted with Ln(DBM-OH)(3)center dot 2H(2)O (where DBM-OH = o-hydroxydibenzoylmethane, Ln = Nd, Er, Yb, and Sin) were prepared through the primary beta-diketone ligand DBM-OH. The structures and optical properties of Ln-DBM-Si were studied in detail. The investigation results revealed that the lanthanide complexes were successfully in situ grafted into the corresponding hybrids Ln-DBM-Si. Upon excitation at the maximum absorption of ligands, the resultant materials displayed excellent near-infrared luminescence.

Effect of silver nanoparticles on luminescent properties of europium complex in di-ureasil hybrid materials

Organic-inorganic hybrids containing luminescent lanthanide complex Eu(tta)(3)Phen (tta = thenoyltrifluoroaceton, phen = 1,10-phenanthroline) and silver nanoparticles have been prepared via mixing rare earth complex and nanoparticles with the precursors of di-ureasil using a sol-gel process. The obtained hybrid materials with transparent and elastomeric features were characterized by transmission electron microscope, solid-state Si-29 magic-angle spinning NMR spectra, diffuse reflectance, UV-visible absorption and photoluminescence spectroscopies. The effect of the silver nanoparticles on the luminescence properties was investigated. The experimental results showed that the luminescence intensity of the Eu(tta)(3)phen complex could be enhanced by less than ca. 9.5 nM of silver nanoparticles with the average diameter of 4 nm, and reached its maximum at the concentration of ca. 3.6 nM. Further increasing the concentration of the silver nanoparticles (> 9.5 nM) made the luminescence quenched. The enchancement and quench mechnism was discussed.

Preparation and luminescence properties of ormosil hybrid materials doped with Tb(Tfacac)(3)phen complex via a sol-gel process

In this paper, silica-based transparent organic-inorganic hybrid materials were prepared via the sol-gel process. Tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used as the inorganic and organic precursors, respectively. The terbium complex, Tb(Tfacac)(3)phen (Tfacac = 1,1,1-trifluoroacetylacetone, phen = 1, 10-phenanthroline) was successfully doped into organically modified silicate (ormosil) matrix derived from TEOS and GPTMS, and the luminescent properties of the resultant ormosil composite phosphors [ormosil/Th(Tfacac)(3)phen] were investigated compared with those of the Tb(Tfacac)(3)phen incorporated into SiO2 derived from TEOS (labeled as silica/Tb(Tfacac)(3)phen). Both kinds of the materials show the characteristic green emission of Tb3+ ion. The luminescence behavior of the resultant composite products was dependent on the matrix composition. The optimized lanthanide complex concentration in the ormosil/Tb(Tfacac)(3)phen was increased compared with in silica/Tb(Tfacac)(3)phen. Furthermore, the lifetime of Tb3+ in Tb(Tfacac)(3)phen, silica/Tb(Tfacac)(3)phen and ormosil/Tb(Tfacac)(3)phen follows the sequence: onmosil/Tb(Tfacac)(3)phen>silica/Tb(Tfacac)(3)phen>pure Tb(Tfacac)(3)phen.

Preparation and luminescence properties of hybrid materials containing europium(III) complexes covalently bonded to a silica matrix

A new kind of luminescent organic-inorganic hybrid material (denoted Hybrid I) consisting of europium 1,10-phenanthroline complexes covalently attached to a silica-based network was prepared by a sol-gel process. 1,10-Phenanthroline grafted to 3-(triethoxysilyl)propyl isocyanate was used as one of the precursors for the preparation of an organic-inorganic hybrid materials. For comparison purposes, the hybrid material (denoted Hybrid II) in which phenanthroline was not grafted onto the silica backbone of the frameworks was also prepared. Elemental analysis; NMR, FT-IR, UV/vis absorption, and luminescence spectroscopies, and luminescence decay analysis were used to characterize the obtained hybrid materials. It is shown that the homogeneity of Hybrid I is superior to that of Hybrid II, and a higher concentration europium can be incorporated into Hybrid I than Hybrid II. Excitation at the ligand absorption wavelength (283 nm) resulted in the strong emission of the Eu3+ D-5(0)-F-7(J) (J = 0-4) transition lines as a result of the efficient energy transfer from the ligands to the EU3+ in Hybrid I. The number of water molecules coordinated to the europium ion was estimated, and the structure of the as-synthesized Hybrid I was predicted on the basis of the experimental results.