Azatranes and atranes of the group 13 elements

This dissertation describes synthesis and reactivity patterns, and the spectral and structural characterization of a series of the group 13 azatranes: (M(RNCH[subscript]2CH[subscript]2)[subscript]3N) [subscript] n (M = B, Al, Ga; R = H, Me, SiMe[subscript]3, SiMe[subscript]2-tert-Bu; n = 1, 2). These azatranes display an oligomeric behavior depending on the nature of the central atom M and the size of the substituents R. Bulky substituents such as SiMe[subscript]3 and SiMe[subscript]2-tert-Bu stabilize monomers with a three-fold molecular symmetry. Single-crystal X-ray diffraction studies on monomeric Al(Me[subscript]3SiNCH[subscript]2CH[subscript]2)[subscript]3N revealed a rare trigonal monopyramidal (TMP) geometry of the aluminum center. The C[subscript]3 propeller-like conformation of these molecules implies the presence of two enantiomers, [delta] and [lambda], whose interconversion (racemization) was observed by variable temperature [superscript]1H NMR spectroscopy in solution for B(Me[subscript]3SiNCH[subscript]2CH[subscript]2)[subscript]3N;Azatranes of Al and Ga possessing smaller equatorial groups form dimers as was shown by multinuclear and two-dimensional NMR spectroscopy experiments. The curious cis configuration of the substituents on the central (M-N)[subscript]2 ring was verified by single-crystal X-ray diffraction studies of three azatranes. The presence of the trans isomer or an interconversion process between the two isomers in solution was ruled out by [superscript]1H and [superscript]13 C NMR spectroscopies in all cases. A series of [superscript]27 Al NMR chemical shifts of monomeric aluminum amides and monomeric and dimeric azaalumatranes containing aluminum ligated exclusively by nitrogens and coordination coordination numbers from three to five displayed a trend toward higher shielding with increasing coordination number;Monomeric and dimeric azaalumatranes and trimethylazaboratrane were found to take part in interesting transmetallation reactions with main-group and transition metal alkoxides and Ga(acac)[subscript]3. By this method, main-group and transition metal azatranes were prepared. Azatranes were also shown to convert to corresponding atranes in a transligation reaction with triethanolamine;The tetrameric nature of alumatrane in solution was substantiated by [superscript]27 Al, [superscript]1 H COSY, and variable temperature [superscript]13 C NMR spectroscopy experiments. The compound displays a complex dynamic behavior including racemization and rotation of the peripheral units

Cu–Ni nanoalloy phase diagram – Prediction and experiment

The Cu-Ni nanoalloy phase diagram respecting the nanoparticle size as an extra variable was calculated by the CALPHAD method. The samples of the Cu-Ni nanoalloys were prepared by the solvothermal synthesis from metal precursors. The samples were characterized by means of dynamic light scattering (DLS), infrared spectroscopy (IR), inductively coupled plasma optical emission spectroscopy (ICP/OES), transmission electron microscopy (TEM, HRTEM), and differential scanning calorimetry (DSC). The nanoparticle size, chemical composition, and Cu-Ni nanoparticles melting temperature depression were obtained. The experimental temperatures of melting of nanoparticles were in good agreement with the theoretical CALPHAD predictions considering surface energy.Fázový diagram nanoslitiny Cu-Ni respektující velikost nanočástic jako další proměnné byl vypočten metodou CALPHAD. Vzorky Cu-Ni nanoslitin byly připraveny solvotermální syntézou z prekurzorů kovů. Tyto vzorky byly charakterizovány pomocí dynamického rozptylu světla (DLS), infračervené spektroskopie (IR) s indukčně vázanou plazmou a optickou emisní spektroskopií (ICP / OES), transmisní elektronovou mikroskopií (TEM, HRTEM) a diferenciální skenovací kalorimetrií (DSC). Velikost nanočástic, chemické složení a Cu-Ni deprese teploty tání nanočástic byly získány experimentálně a v dobré shodě s teoretickou předpovědí metodou CALPHAD s uvážením povrchové energie nanočástic

Structural and functional basis of mammalian microRNA biogenesis by Dicer

MicroRNA (miRNA) and RNA interference (RNAi) pathways rely on small RNAs produced by Dicer endonucleases. Mammalian Dicer primarily supports the essential gene-regulating miRNA pathway, but how it is specifically adapted to miRNA biogenesis is unknown. We show that the adaptation entails a unique structural role of Dicer’s DExD/H helicase domain. Although mice tolerate loss of its putative ATPase function, the complete absence of the domain is lethal because it assures high-fidelity miRNA biogenesis. Structures of murine Dicer⋅miRNA precursor complexes revealed that the DExD/H domain has a helicase-unrelated structural function. It locks Dicer in a closed state, which facilitates miRNA precursor selection. Transition to a cleavage-competent open state is stimulated by Dicer-binding protein TARBP2. Absence of the DExD/H domain or its mutations unlocks the closed state, reduces substrate selectivity, and activates RNAi. Thus, the DExD/H domain structurally contributes to mammalian miRNA biogenesis and underlies mechanistical partitioning of miRNA and RNAi pathways

Study of the anticancer properties of methyl- and phenyl-substituted carbon- and silicon-bridged ansa-titanocene complexes

The previously known complexes {[}Ti\{(Me2CMe2C)(eta(5)-C5H4)(2)\}Cl-2] (1), {[}Ti\{Me2C(eta(5)-C5H4)(2)\}Cl-2] (2), {[}Ti \{Me2Si(eta(5)-C5H4)(2)\}Cl-2] (4), {[}Ti\{MePhSi(eta(5)-C5H4)(2)\}Cl-2] (5) and {[}Ti\{MePhSi(eta(5)-C5Me4)(2)\}Cl-2] (6) have been prepared following reported procedures. The novel complex {[}Ti\{MePhC(eta(5)-C5H4)(2)\}Cl-2] (3) has been prepared and characterized. The cytotoxic activity of 1-6 has been tested after 72 h on melanoma A375 and B16, prostate cancer DU145 and LNCaP and colon cancer HCT116, SW620 and CT26CL25 cell lines observing a high cytotoxic activity of complexes 1 and 6 compared to the reference compound ({[}Ti(eta(5)-C5H5)(2)\}Cl-2]). 1 and 6 have also been tested against primary normal mouse keratinocytes and lung fibroblasts. While viability of both type of primary cells was significantly less affected by 1 in comparison to the reference compound {[}Ti(eta(5)-C5H5)(2)Cl-2], compound 6 was completely nontoxic for nonmalignant cells, indicating a potential selectivity of this compound towards cancer cell lines. In addition CFSE staining, cell cycle analysis, AnnexinV-FITC/PI staining, detection of caspase activity and mitochondrial potential showed that 1 and 6 were acting through inhibition of proliferation and subsequent induction of mitochondrial dependent apoptosis in colon cancer cell lines, HCT116 and SW620, which express low sensitivity to cisplatin. Compound 6 was found to be the leading drug in this group since it shows the fastest and most selective anticancer profile. (C) 2013 Elsevier B.V. All rights reserved.Ministerio de Educacion y Ciencia, Spain {[}CTQ-2011-24346, CTQ-2012-30762]; Ministry of Science and Technological Development of the Republic of Serbia {[}173013]; Grant Agency of the Czech Republic {[}P207/12/2368

Azatranes and atranes of the group 13 elements

This dissertation describes synthesis and reactivity patterns, and the spectral and structural characterization of a series of the group 13 azatranes: (M(RNCH[subscript]2CH[subscript]2)[subscript]3N) [subscript] n (M = B, Al, Ga; R = H, Me, SiMe[subscript]3, SiMe[subscript]2-tert-Bu; n = 1, 2). These azatranes display an oligomeric behavior depending on the nature of the central atom M and the size of the substituents R. Bulky substituents such as SiMe[subscript]3 and SiMe[subscript]2-tert-Bu stabilize monomers with a three-fold molecular symmetry. Single-crystal X-ray diffraction studies on monomeric Al(Me[subscript]3SiNCH[subscript]2CH[subscript]2)[subscript]3N revealed a rare trigonal monopyramidal (TMP) geometry of the aluminum center. The C[subscript]3 propeller-like conformation of these molecules implies the presence of two enantiomers, [delta] and [lambda], whose interconversion (racemization) was observed by variable temperature [superscript]1H NMR spectroscopy in solution for B(Me[subscript]3SiNCH[subscript]2CH[subscript]2)[subscript]3N;Azatranes of Al and Ga possessing smaller equatorial groups form dimers as was shown by multinuclear and two-dimensional NMR spectroscopy experiments. The curious cis configuration of the substituents on the central (M-N)[subscript]2 ring was verified by single-crystal X-ray diffraction studies of three azatranes. The presence of the trans isomer or an interconversion process between the two isomers in solution was ruled out by [superscript]1H and [superscript]13 C NMR spectroscopies in all cases. A series of [superscript]27 Al NMR chemical shifts of monomeric aluminum amides and monomeric and dimeric azaalumatranes containing aluminum ligated exclusively by nitrogens and coordination coordination numbers from three to five displayed a trend toward higher shielding with increasing coordination number;Monomeric and dimeric azaalumatranes and trimethylazaboratrane were found to take part in interesting transmetallation reactions with main-group and transition metal alkoxides and Ga(acac)[subscript]3. By this method, main-group and transition metal azatranes were prepared. Azatranes were also shown to convert to corresponding atranes in a transligation reaction with triethanolamine;The tetrameric nature of alumatrane in solution was substantiated by [superscript]27 Al, [superscript]1 H COSY, and variable temperature [superscript]13 C NMR spectroscopy experiments. The compound displays a complex dynamic behavior including racemization and rotation of the peripheral units.</p

Modification de ligands cyclopentadienyles dans des dichlorures de titanocène et de zirconocène (impact sur leur performance en polymérisation et copolymérisation des oléfines)

DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

WS2 fullerene/plate nanofibers: the tunable crossroad between dimensionalities

Our work describes the nanofibrous materials of tungsten disulfide, which can be tuned by the precursor\u27s crystallinity degree. The carefully formulated nanofibers create the morphological crossroad between fullerenes (0D), nanotubes (1D), plates (2D), and a nonwoven web of nanofibers (3D), containing all the advantageous properties of the presented material categories. Our synthetic methodology (electrospinning, reductive sulfidation) allows scale-up to industrial production. In addition, we studied the optical properties of the WS2 nanofibers using extinction and absolute absorption measurement. The results of the optical analysis further indicate the higher crystallinity of the closed stacked fullerene-based structure. By comparison of the extinction with the absorbance, we find that all the examined nanostructures display typical polaritonic spectra. However, the open plate structure exhibits a stronger scattering and thus better pronounced polaritonic features. Moreover, the ability to control the morphology allows for variating polaritonic features of the final nanofibrous material, which can directly impact the potential optoelectronic and photocatalytic applications

Sintezės temperatūros įtaka T3Sc2Ga3O12 granato, sintetinto skirtingais metodais, faziniam grynumui, kristališkumui bei optinėms savybėms

Mixed-metal garnet (Y3Sc2Ga3O12, YSGG) samples were prepared by: (i) sol– gel, (ii) semi–sol–gel, and (iii) solid state reaction methods. In all the cases, precursor powders were calcined for 10 h at 800 °C in air, ground in an agate mortar and heated again for 10 h at different temperatures in the range of 1000–1400 °C in air atmosphere. The synthesized samples were characterized by X-ray powder diffraction analysis and scanning electron microscopy. It was demonstrated that monophasic Y3Sc2Ga3O12 garnet could be obtained at 1000 °C using the sol–gel technique and at 1200 °C using the semi–sol–gel route

Construction of Larger Molecular Aluminophosphate Cages from the Cyclic Four-Ring Building Unit

New molecular aluminophosphates of different nuclearity are synthesized by a stepwise process and structurally characterized. The alkane elimination reaction of bis(trimethylsiloxy)phosphoric acid, OP-(OH)(OSiMe3)(2), with trialkylalanes, AlR3 (R = Me, Et, Bu-i), provides the cyclic dimeric aluminophosphates, [(AlR2{mu(2)-O2P(OSiMe3)(2)})(2)) (R = Me (1), Et (2), Bu-i (3)). Unsymmetrically substituted cyclic aluminophosphonate [(AlMe2{mu(2)-O2P(OSiMe3)((c)Hex)})(2)] (cis/trans-4) is prepared by dealkylsilylation reaction of (c)HexP(O)(OSiMe3)(2) with AlMe3. Molecules 1-4 containing the [Al-2(mu(2)-O2P)(2)] inorganic core are structural and spectroscopic models for the single four-ring (S4R) secondary building units (SBU) of zeolite frameworks. Compound 1 serves as a starting point in construction of larger molecular units by reactions with OP(OH)(OSiMe3)(2) as a cage-extending reagent and with diketones, such as Hhfacac (1,1,1,5,5,5-hexafluoropentan-2,4-dione) and Hacac (pentan-2,4-dione), as capping reagents. Reaction of 1 with 4 equiv of Hhfacac leads to new cyclic aluminophosphate [(Al(hfacac)(2){mu(2)-O2P(OSiMe3)(2)})(2)] (5), existing in two isomeric (D-2 and C-2h) forms. Reaction of 1 with 2 equiv of OP(OH)(OSiMe3)(2) and 1 equiv of Hhfacac provides a molecular aluminophosphate [AlMe{Al(hfacac)}(2){mu(3)-O3P(OSiMe3)}(2){mu(2)-O2P(OSiMe3)(2)}(2){OP-(OSiMe3)(3)}] (6), while by adding first the Hhfacac and using 3 equiv of OP(OH)(OSiMe3)(2) we isolate [Al{Al(hfacac)}(2){mu(3)-O3P(OSiMe3)}(2){mu(2)-O2P(OSiMe3)(2)}(2)H{OP(O)(OSiMe3)(2)}(2)] (7). These molecules contain units in their cores that imitate 4=1 SBU of zeolite frameworks. Reaction with the order of component mixing 1, Hhfacac, OP(OH)(OSiMe3)(2) at a 1:2:2 molar ratio lead to formation of a larger cluster [(Al(AlMe){Al(hfacac)}{mu(3)-O3P(OSiMe3)}(2){mu(2)-O2P(OSiMe3)(2)}(3))(2)] (8) containing both S4R and 4=1 structural units. Similarly, Hacac (pentan-2,4-dione) provides an isostructural [Al(AlMe){Al(acac)}{mu(3)-O3P(OSiMe3)}(2){mu(2)-O2P(OSiMe3)(2)}(3))(2)] (9). Both molecules display Al centers in three different coordination environments