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Michael Veith Prof. Dr. Dr. h.c. Andreas Rammo Oliver Schütt Volker Huch 《无机化学与普通化学杂志》2010,636(7):1212-1221
The branched tripodal chloro‐methyl‐siloxanes of the general formula tBuSi[{OSiMe2}yOSiMe3–xClx]3 [x = 0–3; y = 0–2] were synthesized, starting with tert‐Butyl‐trisilanol ( 1 ). The treatment of 1 with the chloro‐methyl‐silanes (Me3–xSiClx+1) (x = 0–3) in the presence of triethylamine leads to the compounds tBuSi(OSiMe2Cl)3 ( 2 ), tBuSi(OSiMeCl2)3 ( 3 ) and tBuSi(OSiCl3)3 ( 4 ). The siloxanes 2 – 4 are colourless oily liquids, which can be purified by distillation. Their yields decrease with the number of chloro substituents. In the reaction of compound 2 with three equivalents of water the silantriol tBuSi(OSiMe2OH)3 ( 5 ) is generated which is used to create the branched tripodal chloro‐methyl‐siloxanes tBuSi(OSiMe2OSiMe3)3 ( 6 ), tBuSi(OSiMe2OSiMe2Cl)3 ( 7 ), tBuSi(OSiMe2OSiMeCl2)3 ( 9 ) and tBuSi(OSiMe2OSiCl3)3 ( 10 ). Compound ( 7 ) is only a side product with a yield of 25 %., The cyclic tBuSi[{(OSiMe2)2Cl}(OSiMe2)3O] ( 8 ) can be isolated and characterised. The transformation of the compound tBuSi(OSiMe2OSiMe2Cl)3 ( 7 ) into the trisilanol tBuSi(OSiMe2OSiMe2OH)3 ( 11 ) allows to prepare the tripodale siloxane tBuSi(OSiMe2OSiMe2OSiMe3)3 ( 12 ) in good yields., The reaction of tBuSi(OSiMe2Cl)3 ( 2 ) with tert‐butyl trisilanol 1 leads to the formation of bicyclic tBuSi(OSiMe2O)3SitBu ( 13 ). An X‐ray structure determination on 13 reveals a [3.3.3]‐bicycle with a C3 axis, which crystallizes in the cubic crystal system in the space group Pa . The reported compounds 2 – 13 were characterised by NMR‐ and IR spectroscopy ( 5 , 11 ) and show correct elemental analyses. The 29Si‐NMR‐data of the compounds show interesting trends with respect to the Si–O chain length and the chloro substistuents. 相似文献
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Germanium(II)‐, Zinn(II)‐ und Blei(II)‐Derivate des polycyclischen Alumosiloxans [Ph2SiO]8[Al(O)OH]4
Michael Veith Hinka Hreleva Matthias Gasthauer Andreas Rammo Volker Huch 《无机化学与普通化学杂志》2006,632(6):985-991
Germanium(II)‐, Tin(II)‐ and Lead(II)‐Derivatives of the polycyclic Alumosiloxane [Ph2SiO]8[Al(O)OH]4 Five new derivatives of the polycyclic alumosiloxane [Ph2SiO]8[Al(O)OH]4 have been synthesized by replacement of the protic hydrogen atoms on the hydroxy‐groups attached to the aluminium atoms by the divalent group 14 elements germanium, tin and lead. The compounds can be divided in those with one metal atom per alumosiloxane moiety, [Ph2SiO]8[Al(O)OH]2[AlO2]M (M=Ge, Sn), and those with complete substitution of the protic hydrogen atoms by metal atoms like [Ph2SiO]8[AlO2]4M2 (M= Sn, Pb). Always one element of the series Ge, Sn, Pb is missing in the two types of compounds. Crystal structure analyses of [Ph2SiO]8[Al(O)OH]2[AlO2]2M · 2 C4H8O2 (M= Ge ( 1 ), Sn ( 2a )), [Ph2SiO]8[Al(O)OH]2[AlO2]2Sn · 2 THF ( 2b ) and [Ph2SiO]8[AlO2]4M2 (M= Sn ( 3 ), Pb ( 4 )) have been performed elucidating either polycyclic basket‐type ( 1 , 2a , 2b ) or closed polyhedral structures ( 3 , 4 ). 相似文献
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I. Rammo M. Kerikmyaé M. Lepist L. Matizen L. Pung K. Ritslaid A. Haav 《Journal of Applied Spectroscopy》1997,64(2):182-187
It is found that the shape of luminescence spectra of SrS−Ce phosphors is independent of both the species and concentration
of a cofactor F, Cl, Br, or 1 introduced in the form of ammonium halide at least up to 6.5 at.%. The only exception is F,
which, when added as a coactivator with a concentration of 2.4 at.% and above, gives rise to new longwave luminescence bands,
part from the luminescence of the Ce3+ ion. Analysis has shown that this additional luminescence spectrum is similar to the Ce3+ spectrum but is shifted towards the longwave region by about 0.14 eV. The luminescence decay time constant (τ=57 nsec) is
very close to Br, I, and small concentrations of F, a model is valid according to which the halogen that substitutes for sulfur
and the Ce3+ that substitutes for Sr are the closest neighbors not to each other, but to a probable compensator of the charge of Sr vacancies.
At high concentrations of fluorine some of the F ions are located at interstitial lattice sites in the immediate neighborhood
of Ce3+, providing compensation for the charge of Ce3+ ions and having a marked effect on them.
Tartu University, 18, Ulikooli St., Tartu EE2400, Estonian Republic. Translated from Zhurnal Prikladnoi Spektroskopii, Vol.
64, No. 2, pp. 173–178, March–April, 1997. 相似文献
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Matt Rammo Dr. Aleksander Trummal Dr. Merle Uudsemaa Juri Pahapill Katrin Petritsenko Dr. Meelis-Mait Sildoja Dr. Charles W. Stark Dr. Sigrid Selberg Prof. Ivo Leito Kirsti Palmi Dr. Jasper Adamson Prof. Aleksander Rebane 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202103707
Lipophilic fluorophores are widely implemented in nonlinear microscopy; however, few existing membrane-specific probes combine the high brightness of two-photon excited fluorescence (2PEF) with pH sensitivity. Herein we describe four novel two-photon excited fluorophores, based on a coumarin 151 core structure, where lipophilicity is induced by a covalently attached phosphazene moiety. Changing the environmental acidity using trifluoromethanesulfonic (triflic) acid leads to profound changes in the linear fluorescence and 2PEF characteristics, due to chromophores’ switching between neutral- and protonated forms. We characterize this dependence by measuring the two-photon absorption (2PA) spectra over the region λ2PA=550–1000 nm, observing 2PA cross sections of σ2PA=10–20 GM, with an associated 2PEF brightness of 10–13 GM, in neutral solutions of both acetonitrile and n-octanol. Although quantum chemical modelling and NMR measurements show that, at high chromophore concentrations, protonation may be accompanied by a dimerization process, these dimers likely do not form at the lower concentrations used in optical spectroscopy. 相似文献
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We have studied the photoluminescence of calcite crystals. In the blue region of the photoluminescence spectrum of calcite
crystals obtained from Siberia (Russia) and from Saaremaa Island (Estonia), three strongly overlapping luminescence bands
due to intrinsic defects are observed. Luminescence due to impurities in the crystals are hardly detectable. The experimentally
measured time dependence of the luminescence intensity for the indicated luminescence bands is compared with the dependences
obtained as a result of a calculation based on a proposed model for the luminescence center. Better agreement between experiment
and calculation is achieved if the model of the luminescence center includes a metastable level with electron ejection energy
of 4 meV; the characteristic time for the radiative transition is 1.3 nsec. Studying the time dependence of the luminescence
at different wavelengths within the indicated bands allows us to conclude that the photoluminescence (three bands) is due
to one type of luminescence center.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 498–501, July–August, 2006. 相似文献
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The synthesis of poly(pentamethylene terephthalate) and its subsequent drawing into highly oriented fiber has proved difficult for two reasons. First, it was difficult to produce polymers of sufficiently high molecular weight to withstand subsequent drawing; and second, because of the slow rate of crystallization of the material, the spun fiber coalesced on the windup bobbin, becoming useless for drawing. Methods are described which overcome these difficulties. Two crystalline phases of the oriented fiber have been discovered. The α form is obtained by annealing under zero or small tension and has a crystallographic repeat along the fiber axis of 24.7 Å compared with a chemical repeat of 14.5 Å. There are evidently two monomers per crystallographic repeat, each appreciably contracted. The β form is obtained by annealing either under high tension or at constant extended length, but in the relaxed fiber it always exists in mixture with the α form. Its crystallographic repeat is 28.2 Å, and so again consists of two monomers; but their conformation is more highly extended than that of the α form. An α-form fiber will transform reversibly to the β form under the influence of mechanical stress. 相似文献
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The oligoalumosiloxanes {[Ph2SiO]8[Al(O)OH]4·2,5Et2O·HOtBu} ( 6 ) and {[Ph2SiO]8[Al(O)OH]4·2Et2O·2HOiPr} ( 7 ) have been obtained from the reaction of diphenylsilanediol with aluminium‐tri‐tert‐butoxide and aluminium‐tri‐iso‐propoxide in ethyl ether with reasonable yields. In a 1:1 molar mixture of toluene and the respective alcohol (iso‐propanol or tert‐butanol), the ethyl ether molecules in {[Ph2SiO]8[Al(O)OH]4·4Et2O}, in 6 or 7 can be completely displaced forming the compounds [Ph2SiO]8[Al(O)OH]4·4HOiPr ( 8 ) and [Ph2SiO]8[Al(O)OH]4·nHOtBu ( 9 ). Whereas 6 , 7 and 8 are crystalline, 9 is obtained as a viscous liquid. An X‐ray structure determination on {[Ph2SiO]8[Al(O)OH]4·3Et2O·HOtBu} reveals different bonding modes of the diethyl ether molecules to the oligoalumosiloxane compared to the tert‐butanol, which forms two hydrogen bonds (one to the OH‐group of the inner Al4(OH)4 cycle and one through the alcohol OH‐group to a Si–O–Al moiety. The alcohol adducts have been characterized in solution through 1H‐, 13C‐ and 29Si‐NMR and show dynamic equilibria between the oligoalumosiloxane [Ph2SiO]8[Al(O)OH]4 and the alcohol molecules. 相似文献