Synthesis of the first rare earth metal bis(alkyl)s bearing an indenyl functionalized N-heterocyclic carbene

Treatment of indenyl-modified imidazolium bromide [C9H7CH2CH2(NCHCHN(C6H2Me3-2,4,6)CH)Br] ((IndH-NHC-H)Br) with rare earth metal tetra(alkyl) lithium (Ln(CH2SiMe3)(4)Li(THF)(4)) or with (trimethylsilylmethyl)lithium (LiCH2SiMe3) and rare earth metal tris(alkyl)s (Ln(CH2SiMe3)(3)(THF)(2)) sequentially afforded the first NHC-stabilized monomeric rare earth metal bis(alkyl) complexes (Ind-NHC)Ln(CH2SiMe3)(2) (1, Ln = Y; 2, Ln = Lu; 3, Ln = Sc) via double-deprotonation reactions. Complexes 1-3 are THF-free isostructural monomers. The monoanionic Ind-NHC species bond to the central metal ion in a eta(5):kappa(1) constrained geometry configuration (CGC) mode, which combine with the two cis-located alkyl moieties to form a tetrahedron ligand core, leading to the chirality of the complexes. Under the presence of activators AlEt3 and [Ph3C][B(C6F5)(4)], complex 2 showed catalytic activity toward the polymerization of isoprene to afford 3,4-regulated polyisoprene (91%).

Triblock poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid)/paclitaxel conjugates: Synthesis, micellization, and cytotoxicity

A triblock poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid) (PLA-PEG-PLA)/paclitaxel (PTX) conjugate was synthesized by the reaction of carboxyl-terminated copolymer PLA-PEG-PLA with PTX in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine. Carboxyl-terminated copolymer PLA-PEG-PLA was prepared by the reaction of the hydroxyl end groups in copolymer PLA-PEG-PLA with succinic anhydride. Its structure was confirmed by NMR and gel permeation chromatography. The PLA-PEG-PLA/PTX conjugates could self-assemble into micelles in aqueous solutions with a low critical micelle concentration. Dynamic light scattering and environmental scanning electron microscopy analyses of the PLA-PEG-PLA/PTX micelles revealed their spherical structure and size of 220 nm. The antitumor activity of the conjugate against woman Hela cancer cells, evaluated by the 3-(4,5-dimethylthiazol2-yl)-2,5-diphenyl tetrazolium bromide method, showed that the conjugates had an antitumor activity similar to that of pure PTX. The obtained PLA-PEG-PLA/PTX conjugates are expected to be used in clinical practice.

The study of synthesis of poly(ethylene oxide)-b-poly(N,N-dimethylacrylamide) by atom transfer radical polymerization and self-assembly in selective solvents

Poly( ethylene oxide)-b-poly(N, N-dimethylacrylamide) (PEO-b-PDMA) was synthesized by successive atom transfer radical polymerization (ATRP) of N, N-dimethylacrylamide (DMA) monomer using PEO-Br macro initiators as initiator, CuBr and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazamacrocyclotetra decane (Me-6[14] aneN(4)) as catalyst and ligand. PEO-Br macroinitiator was synthesized by esterification of PEO with 2-bromoisobutyryl bromide. GPC and H-1 NMR studies show that the plot of ln([DMA](0)/[ DMA]) against the reaction time is linear, and the molecular weight of the resulting PDMA increased linearly with the conversion. Within 3 h, the polymerization can reach almost 60% of conversion. PEO-b-PDMA copolymer with low polydispersity index (M-w/M-n approximate to 1.1) is obtained. Self-assembly of PEO-b-PDMA in selective solvents is also studied. It could self-assemble into micelles in methanol/acetone (1/10, v/v) solution. TEM analyses of the PEO-b-PDMA micelles with narrow size distribution revealed that their size and shape depend much on the copolymer composition.

Electrosynthesis and characterization of 1,2-dibenzyl C-60: A revisit

A reinvestigation of the reaction between C-60(2-) and benzyl bromide in benzonitrile containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) has shown that there are more reaction products than previously reported. Use of a silica rather than a "Buckyclutcher I" column for HPLC purification led to isolation of two previously unattained products in the reaction mixture, one of which was identified as 1,2-(PhCH2)(2)C-60 by UV-vis and NMR. The earlier incorrectly assigned 1,2-(PhCH2)(2)C-60 was identified as the methanofullerene C61HPh by X-ray single-crystal diffraction. The electrochemistry of genuine 1,2-(PhCH2)(2)C-60 shows that its first reduction potential in PhCN containing 0.1 M TBAP is cathodically shifted by 100 mV with respect to E-1/2 for reduction of 1,4-(PhCH2)(2)C-60, indicating that the addition pattern significantly affects the electrochemistry of derivatized C-60. Visible and near-IR spectra of the monoanion and dianion of 1,2-(PhCH2)(2)C-60 are also reported.

Robust core-shell supramolecular assemblies based on cationic vesicles and ring-shaped {Mo-154} polyoxomolybdate nanoclusters: Template-directed synthesis and characterizations

Substantial progress has been made recently in extending the supramolecular assembly of biomimetic structures to vesicle-based sophisticated nanocomposites and mesostructures. We report herein the successful preparation of unilamellar surfactant vesicles coated with a monolayer of ring-shaped {Mo-154} polyoxometalate (POM) nanoclusters, (NH4)(28)[Mo-154 (NO)(14)O(448)Hi(4)(H2O)(70)].approximate to 350H(2)O, by coulomb attractions using preformed didodecyldimethylammonium bromide (DDAB) surfactant vesicles as templates. The resultant vesicle-templated supramolecular assemblies are robust (they do not disintegrate upon dehydration) both at room-temperature ambient and vacuum conditions, as characterized by conventional transmission electron microscopy (TEM) and atomic force microscopy (AFM). The flexibility of the complex soft assemblies was also revealed by AFM measurements. The effect of POM-vesicle coulomb attractions on the dimensions of the templating vesicles was also investigated by using dynamic light scattering (DLS).Although origins of the structure stability of the as-prepared supramolecular assemblies are not clear yet, the nanometer scale cavities and the related properties of macroions of the POM clusters may play an important role in it.

Stable ordered mesoporous silica materials templated by high-temperature stable surfactant micelle in alkaline media

Ordered hexagonal mesoporous silica material (JLU-30) has been successfully synthesized in alkaline media at high temperature (> 160 degreesC, using cationic (1,3-dimethyl-2-imidazolidin-2-ylidene)hexadecylmethyl-ammonium bromide (DIHAB) as a template, and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, differential thermal analysis (DTA), and thermogravimetric analysis (TG), as well as Al-27 and Si-29 nuclear magnetic resonance (NMR) spectroscopy. Mesoporous JLU-30 shows much higher hydrothermal stability than MCM-41. Si-29 NMR spectra indicate that the pore walls of JLU-30 samples synthesized at high temperature (160 degreesC) are fully condensed, giving a Q(4)/Q(3) ratio as high as 6.2. In contrast, MCM-41 synthesized at relatively low temperature (100 degreesC) shows the Q(4)/Q(3) + Q(2) ratio at 1.1. Such unique structural feature might be responsible for the observed highly hydrothermal stability of the mesoporous silica materials (JLU-30).

Synthesis, characterization and ring-opening polymerization of cyclic (arylene phosphonate) oligomers

A series of cyclic (arylene phosphonate) oligomers were prepared by reaction of phenylphosphonic dichloride (PPD) with various bisphenols under pseudo-high dilution conditions via interfacial polycondensation. The yield of cyclic (arylene phosphonate) oligomers is over 85% by using hexadecyltrimethylammonium bromide as phase transfer catalyst (PTC) at 0 degreesC. The structures of the cyclic oligomers were confirmed by a combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and IR analysis. These cyclic oligomers undergo facile ring-opening polymerization in the melt by using potassium 4,4'-biphenoxide as the initiator to give linear polyphosphonate. Free-radical ring-opening polymerization of cyclic(arylene phosphonate) oligomers containing sulfur linkages was also performed in the melt using 2,2'-dithiobis(benzothiazole) (DTB) as the initiator at 270degreesC and the resulting polymer had a M-w of 8 x 10(3) with a molecular weight distribution of 4. Ring-opening copolymerization of these cyclic oligomers with cyclic carbonate oligomers was also achieved. The average molecular weight of the resulting copolymer is higher than the corresponding, homopolymer and the thermal stability of the copolymer is better than the corresponding homopolymer.

Synthesis and photoluminescence properties of erbium-doped BaF2 nanoparticles

Erbium-doped BaF2 nanoparticles were prepared from the microemulsion of cetyl trimethyl ammonium bromide (CTAB), n-butanol, n-octane and water. The X-ray diffraction (XRD) patterns were indexed to a pure BaF2 cubic phase. Transmission electron microscopy (TEM) images showed that BaF2 products were monodispersed with 15-20 nm in size at the dopant concentration of 0.06 mol%. At higher dopant concentration, there was no significant increase in particle size, but more polydispersed. Photoluminescence (PL) properties of the final products were examined. We can observe fluorescence of Er3+ around 1540 nm and with the increase of dopant concentration, the fluorescent intensity increases.

Surprising arching sheet-like dendrites growing from BaF2 nanocubes

BaF2 nanocubes were prepared from quaternary reverse micelles of cetyl trimethyl ammonium bromide (CTAB), n-butanol, n-octane, and water. Interestingly, there are arching sheet-like dendrites growing between two neighbouring sides of these cubes. X-ray powder diffraction (XRD) analysis showed that the products were BaF2 single phase. Scanning electron microscopy (SEM) or transition electron microscopy (TEM) was used to estimate the size of the final products. The results showed that the shape and size of particles were strongly dependent on the reaction conditions, such as the temperature and reaction time. When the reaction temperature was 25 degreesC, we obtained cuboid-like particles with 'clean' surfaces (no dendrites growing on them), and when the temperature was 35 degreesC, we obtained nanocubes with dendrites growing from them between the neighbouring sides. The influence of reaction time at a temperature of 35 degreesC is also discussed.

Synthesis and fluorescence of europium-doped barium fluoride cubic nanocolumns

Europium-doped barium fluoride cubic nanocolumns were synthesized from the quaternary water in oil reverse microemulsions In this process, the aqueous cores of water/cetyl trimethyl ammonium bromide (CTAB)/n-butanol/n-octane reverse microemulsions were used as microreactors for the precipitation of europium doped barium fluoride. XRD analysis shows that under the dopant concentration of 0.06% (molar fraction), the products are single phase. The result products are cubic column-like with about 30 similar to 50 nm edge length of cross section, and about 200 nm of length obtained from the transmission electron microscopy (TEM), and atomic force microscopy (AFM). Under the 0.06 % (molar fraction) of dopant concentration I the fluorescence of Eu2+ and Eu3+ under the 589 of excitation wavelength is observed.

Synthesis of barium lithium fluoride nanocrystals using reverse micelles as microemulsion

Barium lithium fluoride nanocrystals were synthesized in cetyltrimethylammonium bromide (CTAB)/2-octanol/water microemulsion systems. The impurity peaks in XRD patterns were not determined. The result of SEM confirmed that the average sizes and shape of the BaLiF3 nanocrystals. The formation of BaLiF3 and particles size were strongly affected by water content. With increasing water content and reaction times, the size of the particle. increases. Meanwhile, the solvent was also found to play a key role in the synthesis of the BaLiF3 nanocrystals.

Luminescent Langmuir-Blodgett films based on Tiron-terbium

The luminescent ultrathin Langmuir-Blodgett (LB) films containing Tb-2(C6H3S2O8)(2) (Tiron-Tb) were successfully obtained. The modifications of compression isotherms of dimethyldioctadecylammonium bromide (DODA) have been observed when the Tiron-Tb complex was dissolved in the subphase. The effect of Tiron-Tb in the subphase on Langmuir films of DODA has been studied. Low-angle X-ray diffraction result indicates that the LB films have a good periodic layered structure. The UV and IR spectra results show the Tiron-Tb complex is incorporated into LB films layer-by-layer and the LB films are homogeneously deposited. The LB films containing Tiron-Tb can emit strong green luminescence, and the luminescence signal can be detected from a single layer. The luminescence properties of LB films have been discussed compared with those of the solutions.

Luminescent hybrid Langmuir-Blodgett films of polyoxometaloeuropate

Luminescent hybrid Langmuir-Blodgett (LB) films of polyoxometaloeuropate (Na9EuW10O36) were successfully prepared. Low-angle X-ray diffraction data demonstrate that the LB films have a well-defined lamellar structure. The hybrid LB films can exhibit strong luminescence under UV irradiation, which can be observed by the human eye. The effect of the lipid ocradecylamine, on the luminescence of polyoxometaloeuropate was discussed and compared with that of the lipid dimethyldioctadecylammonium bromide. It is found that the intensity ratio for the D-5(0) --> F-7(2) transition to the D-5(0) --> F-7(1) transition of europium in two kinds of LB films is quite different. The X-ray photoelectron spectra data verify that there exist different interactions between two lipids and the inorganic polyanions. The different interactions between two lipids and the polyanions may result in the distortion of the site symmetry for europium to a different extent, which may account for the difference in luminescent behavior between the two kinds of LB films.

Effects of a surfactant on the electrocatalytic activity of cobalt hexacyanoferrate modified glassy carbon electrode towards the oxidation of dopamine

The cobalt hexacyanoferrate film (CoHCF) was deposited on the surface of a glassy carbon (GC) electrode with a potential cycling procedure in the presence and absence of the cationic surfactant, cetyl trimethylammonium bromide (CTAB), to form CoHCF modified GC (CoHCF/GC) electrode. It was found that CTAB would affect the growth of the CoHCF film, the electrochemical behavior of the CoHCF film and the electrocatalytic activity of the CoHCF/GC electrode towards the electrochemical oxidation of dopamine (DA). The reasons of the electrochemical behavior of CoHCF/GC electrode influenced by CTAB were investigated using FTIR and scanning electron microscope (SEM) techniques. The apparent rate constant of electrocatalytic oxidation of DA catalyzed by CoHCF was determined using the rotating disk electrode measurements.

Synthesis and characterization of functionalized mesoporous silica by aerosol-assisted self-assembly

An efficient, productive, and low-cost aerosol-assisted self-assembly process has been developed to produce organically modified mesoporous silica particles via a direct co-condensation of silicate species and organosilicates that contain nonhydrolyzable functional groups in the presence of templating surfactant molecules. Different surfactants including cetyltrimethylammonium bromide, nonionic surfactant Brij-56, and triblock copolymer P123 have been used as the structure-directing agents. The organosilanes used in this study include tridecafluoro-1, 1,2,2-tetrahydrooctyltriethoxysilane, methytriethoxysilane, vinyltrimethoxysilane, and 3-(trimethoxysilyl)propyl methacrylate. X-ray diffraction and transmission electron microscopy studies indicate the formation of particles with various mesostructures. Fourier transform infrared and solid-state nuclear magnetic resonance spectra confirm the organic ligands are covalently bound to the surface of the silica framework. The porosity, pore size, and surface area of the particles were characterized using nitrogen adsorption and desorption measurements.