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1.
Hitomi Saito Yuki Nishio Manabu Kobayashi Yoshiyuki Sugahara 《Journal of Sol-Gel Science and Technology》2011,57(1):51-56
The hydrolysis behavior of 1,4-bis(triethoxysilyl)benzene (BTB), a precursor of bridged polysilsesquioxane, was investigated
with high-resolution 29Si nuclear magnetic resonance (29Si NMR) spectroscopy at ambient temperature in a system with BTB:ethanol:water:HCl = 1:10:x:0.8 × 10−4 (x = 3, 6 or 9). Signals due to hydrolyzed triethoxysilyl groups as well as unhydrolyzed triethoxysilyl groups [−Si(OEt)3, −Si(OEt)2(OH), −Si(OEt)(OH)2 and −Si(OH)3 (OEt = OCH2CH3)] formed four sub-regions based on the number of hydroxyl groups bound to a silicon atom. In addition, one silicon environment
influenced the other silicon environment by an intra-molecular interaction between two silicon atoms, and each sub-region
for monomeric species thus contained four signals. Based on the development of signal intensity, it is revealed that one of
the two triethoxysilyl groups in BTB is hydrolyzed preferentially. Thus, when a triethoxysilyl group is hydrolyzed, the −Si(OH)
x
(OEt)3−x
(x = 1, 2) groups formed undergo further hydrolysis, which is opposite to the tendency expected from the hydrolysis behavior
of organotrialkoxysilanes under acidic conditions. 相似文献
2.
The structural change near the phase transition temperatures of [NH2(CH3)2]2CuCl4 is discussed in terms of the chemical shifts and the spin-lattice relaxation times T1ρ in the rotating frame for 1H MAS NMR and 13C CP/MAS NMR. The 1H T1ρ undergoes molecular motion near the phase-transition temperature (TC2 = 253 K). In addition, the two inequivalent [NH2(CH3)2] (1) and [NH2(CH3)2] (2) sites were distinguishable by the 13C chemical shift. And, the most significant change was observed at TC2 for the 13C CP/MAS NMR spectrum; this temperature corresponds to a ferroelastic phase transition with different orientations. 相似文献
3.
1,3-Bis[(triethoxysilyl)methyl]tetrahydropyrimidin-2-one and 1,3-bis[(dimethoxysilyl)methyl]tetrahydro-pyrimidin-2-one have
been synthesized on interacting urea with N,N′-bis(silylmethyl)propylenamines (EtO)3−nMenSiCH2NH(CH2)3NHCH2SiMen(OEt)3−n (n = 0, 2). Their interaction with boron trichloride has been studied. The structures of all the compounds synthesized have
been demonstrated by multinuclear NMR spectroscopy.
Dedicated to the 50th Anniversary of the Latvian Institute of Organic Synthesis
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 238–244, February, 2007. 相似文献
4.
N. V. Stolyarchuk I. V. Mel’nik G. I. Dobryanskaya Yu. L. Zub B. Alonso 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(6):935-940
1H magic angle spinning NMR spectroscopy was used to study xerogels containing the 3-mercaptopropyl group. These xerogels were synthesized using tetraethoxysilane, 1,2-bis(triethoxysilyl)ethane, and 1,4-bis(triethoxysilyl)benzene as structuring agents. The assignment of the NMR signals observed showed the presence of thiol groups introduced during syntheses and organic bridges in the frame of polysilsesquioxane samples. An analysis of the 1H magic angle spinning NMR spectra also showed the presence of small amounts of alcohols, water participating in H-bonding, and nonhydrolyzed alkoxyl groups in the xerogels. In several instances, the structural units of T n and Q m types present in the xerogels were identified. The 1H magic angle spinning NMR spectroscopy combined with 13C and 29Si solid-state NMR spectroscopy allows the composition of xerogels and the nature of the structural units they contain to be identified more thoroughly and reliably. 相似文献
5.
Polysiloxane xerogels containing 3-mercaptopropyl and methyl groups in the surface layer were synthesized by the sol-gel method with ethanol used as a solvent and fluoride ion used as a catalyst. It is established that an increase in the relative content of methyltriethoxysilane in the initial reaction mixture results in formation of xerogels with a developed porous structure. The tendency for an increase in other characteristics of porous structure, the sorption volume and pore size, is also observed. The analogous effect is found upon increasing relative content of tetraethoxysilane with a constant ratio between two trifunctional silanes. By means of atomic force microscopy, it is shown that the xerogels are composed of aggregated particles with mean sizes of 35–45 nm. These results correlate with the data of scanning electron microscopy. On the basis of the data of IR spectroscopy and 13C CP/MAS NMR spectroscopy, it is concluded that the surface layers contain not only 3-mercaptopropyl and methyl groups but also silanol groups, a part of the unhydrolyzed alkoxy groups, and water molecules involved in the formation of hydrogen bonds. The results obtained by 29Si CP/MAS NMR spectroscopy testify that, in synthesized xerogels, the structural units of T1 type [(≡SiO)Si(OR′)2CH3 and/or (≡SiO)Si(OR′)2(CH2)3SH, R′ = H, OCH3 or OC2H5] are absent and the structural units of T3 type [(≡SiO)3SiCH3 and (≡SiO)3Si(CH2)3SH] dominate compared to the units of T2 type [(≡SiO)2Si(OR′)CH3 and (≡SiO)2Si(OR′)(CH2)3SH]. These results are an indirect indication of enhanced hydrolytic stability of surface layers in such xerogels. 相似文献
6.
Jessie Casimiro Bénédicte Lepoittevin Caroline Boisse-Laporte Marie-Geneviève Barthés-Labrousse Pascale Jegou Fran?ois Brisset Philippe Roger 《Plasma Chemistry and Plasma Processing》2012,32(2):305-323
With the aim of introducing primary amino groups on the surface of poly(ethylene terephthalate) (PET), two methods were compared—the
use of ammonia or a combination of nitrogen and hydrogen low-pressure microwave plasma. Several plasma parameters were optimized
on the reactor to increase the –NH2 surface density, which was estimated by colorimetric titration and X-ray photoelectron spectroscopy (XPS). These techniques
show that whatever the plasma treatment, almost 2 –NH2/nm2 are incorporated on PET films. Emission spectroscopy highlighted a correlation between the density of primary amino groups
and the ratio between an NH peak intensity and an Ar peak intensity (INH/IAr). Variation in surface hydrophilicity with aging in air after plasma treatment was monitored with contact angle measurements
and showed a hydrophobic recovery. This was confirmed by XPS, which suggests also that surfaces treated by NH3 plasma are more stable than surfaces treated by N2/H2. 相似文献
7.
Khaled S. Abou-El-Sherbini Carola Pape Olaf Rienetz Detlef Schiel Rainer Stosch Peter G. Weidler Wolfgang H. Höll 《Journal of Sol-Gel Science and Technology》2010,53(3):587-597
Silanol groups of n-aminopropyl silica gel (APSG) were blocked with TiO2 or ZrO2 to produce Ti-APSG and Zr-APSG, respectively. The silica materials were characterized by infrared, Raman spectra, thermogravimetric,
elemental analyses, magic angle spinning 13C-nuclear magnetic resonance, specific surface area measurements, pH-metric titration and inductively coupled plasma—optical
emission spectrometry—monitored silica hydrolysis. The stability of APSG against hydrolysis was found to be mainly affected
by the specific surface area and the basicity of the n-aminopropyl groups which acquire additional strength from their intramolecular interaction with the silanol groups. The hydrolysis
of silica in Ti-APSG and Zr-APSG remarkably decreased in the range of pH 1.0–9.1 due to the interruption of that intramolecular
interaction. The hydrolyzed silica of Ti-APSG and Zr-APSG was decreased to 22.7 and 29.9%, respectively, of that of APSG at
pH 4.5. Capacity and stability of Ti-APSG and Zr-APSG were improved in comparison with APSG upon application in the extraction
of Cu2+ for 20 cycles of extraction and regeneration. 相似文献
8.
Xerogels containing residues of amide derivatives of phosphonic and thiophosphonic acids, ≡Si(CH2)3NHP(S, O)(OC2H5)2 (functional group concentration of 1.3–2.2 mmol/g) have been prepared by a sol-gel method. It has been shown that xerogels having a developed porous structure (with specific surface areas of 240–485 m2/g, pore volumes of 0.20–0.50 cm3/g, and pore diameters of 3.6–6.5 nm) are formed at tetraethoxysilane-to-trifunctional silane ratios of 4: 1 (and above) and 6: 1 (and above) for the derivatives of phosphonic and thiophosphonic acids, respectively. The IR and 13C CP/MAS NMR spectroscopy data have demonstrated that the surface layer of the xerogels contains not only (thio)phosphonic acid residues, but also silanol groups and water molecules participating in hydrogen bonding. The 29Si CP/MAS NMR spectroscopy data have indicated that structural groups are, for the most part, contained in structural units T3 [(≡SiO)3Si(CH2)3NHP(O, S)(OC2H5)2] and T2 [(≡SiO)2Si(OR)[(CH2)3NHP(O, S)(OC2H5)2] (R = H or C2H5). 相似文献
9.
V. R. Akhmetova E. B. Rakhimova A. B. Minnebaev R. V. Kunakova N. F. Galimzyanova 《Russian Journal of Organic Chemistry》2012,48(2):202-208
Cyclothiomethylation was performed of heterochain (O, S-S, NH) α,ω-diamines with formaldehyde and H2S in aqueous medium at 20–60°C to obtain new α,ω-bis(1,3,5-dithiazinanes). The cyclocondensation of N-(3-aminopropyl)butane-1,4-diamine
(spermidine), formaldehyde, and H2S proceeds efficiently in the medium of BuOH-H2O at 0°C and leads to the formation of previously unknown O,S-containing macroheterocycle, 1,7-dioxa-3,5,9,11-tetrathiacyclododecane.
A fungicidal activity was found in 5,5′-(3,6-dioxaoctane-1,8-diyl)bis-1,3,5-dithiazinane with respect to microscopic fungi
affecting agriculture. 相似文献
10.
Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the
fusion enthalpy and temperature determination of the biuret (NH2CO)2NH (synthesis by-product of the urea fertilizer (NH2)2CO). Recommended values are Δm
H = (26.1 ± 0.5) kJ mol−1, T
m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems
to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature
of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested. 相似文献
11.
V. V. Semenov E. Yu. Ladilina S. Ya. Khorshev N. P. Makarenko Yu. A. Kurskii O. A. Bochkova 《Russian Chemical Bulletin》1998,47(12):2455-2462
The reaction of (HMe2Si)2NH with Co2(CO)8 gives the complex [Co2(CO)7(SiMe2)2NH2]+[Co(CO)4]−. Its thermal decomposition starts with dissociation into the “acid” HCo(CO)4 and the “base” Co2(CO)7(SiMe2)2NH. After that, the base and the initial complex decompose further under the action of HCo(CO)4. The final products of this reaction are CO, NH3, Co, volatile dimethylcyclosilazane, and a solid residue consisting of cobalt particles encapsulated into a polymethylsiloxane
matrix and possessing properties of mixed para- and ferromagnetics with an ultimate specific magnetization of 64–74 G g−1. Tetramethyldisilazane reacts with iron pentacarbonyl under UV irradiation to give relatively stable 1,3-bis(tetracarbonylthydrideiron)-1,1,3,3-tetramethyldisilazane.
This product contains Fe−H…N hydrogen bonds, which stabilize it against dehydrogenation and cyclization to diironcyclodisilazane.
Thermal decomposition of this product was investigated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2537–2544, December, 1998. 相似文献
12.
Xabier Rios Paula Moriones Jesús C. Echeverría Asunción Luquín Mariano Laguna Julián J. Garrido 《Adsorption》2011,17(3):583-593
The mild synthetic conditions provided by the sol-gel process and the versatility of the colloidal state allow for the mixing
of inorganic and organic components at the nanometre scale in virtually any ratio for the preparation of hybrid materials.
Our interest in hybrid xerogels focuses on combining their porosity with other properties to prepare optic-fibre sensors.
The specific aim of this paper is to synthesise hybrid xerogels in acid media using methyltriethoxysilane (MTEOS) and tetraethoxysilane
(TEOS) as silica precursors and to investigate the effect of the MTEOS molar ratio on the structure and porous texture of
xerogels. Gelation time exponentially increased as the MTEOS molar ratio increased. Increasing the MTEOS molar ratio yielded
xerogels with lower density and lower particle size. The incorporation of MTEOS resulted in new FTIR bands at 1276 and 791 cm−1, which was attributed to vibrational modes of methyl group. The band around 1092 cm−1 associated with siloxane bonds shifted to lower wavenumbers and split into two bands. The 29Si spectra only showed the Q
n
(n=2, 3, 4) signal in xerogels with 0% MTEOS and the T
n
(n=2, 3) signal in xerogels with 100% MTEOS; hybrid xerogels showed both Q and T signals. From XRD peaks at 2θ around 9°, we inferred that xerogels (>70% MTEOS) consisted of nanocrystalline CH3–SiO3/2 species. Increasing the MTEOS molar ratio produced xerogels with lower pore volumes and lower average pore size. The integration
of methyl groups on the surface decreased the surface polarity and, in turn, the characteristic energy. 相似文献
13.
E. V. Starodubtseva O. V. Turova M. G. Vinogradov L. S. Gorshkova V. A. Ferapontov 《Russian Chemical Bulletin》2005,54(10):2374-2378
The rate of hydrogenation of γ-ketoesters MeCOCH2CH2COOR (R = Et, Pri, But) in the presence of the chiral RuII—BINAP catalyst (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5–10 equivalents
of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially
formed would cyclize by ∼95% to give γ-valerolactone with optical purity of 98–99% ee. When the Ru(COD)(MA)2—BINAP—HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester
(R = Et) in EtOH is attained in 5 h at 60 °C under an H2 pressure of 60–70 atm.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2301–2304, October, 2005. 相似文献
14.
Lianbin Wu Qiu Chen Zhiqing Lv Weilin Sun Limin Chen Jirong Wu 《Journal of Sol-Gel Science and Technology》2011,60(2):214-220
A novel alkoxysilylated derivative based on 2,2′-diamino-4,4′-bithiazole (DABTH) was firstly synthesized. The corresponding
polysilsesquioxane (PBSIBTH) and its metal complexes (PBSIBTH-Eu3+, PBSIBTH-Tb3+ and PBSIBTH-Ni2+) were also obtained via sol–gel method, respectively. The morphology of their xerogels was investigated by scanning electron
microscopy means. The magnetic measurements of these polymer complexes show all obtained solid materials feature soft ferromagnet
properties at low temperature. The metal ions in polymer complexes have a significant influence on both microstructure and
magnetic properties. 相似文献
15.
I. V. Mel’nik N. V. Stolyarchuk L. I. Kozhara V. P. Goncharik Yu. L. Zub 《Russian Journal of General Chemistry》2013,83(8):1613-1620
Two xerogels with the ligand groups concentration 1.0 and 1.8 mmol gs?1 were prepared by sol-gel method from 1,2-bis(triethoxysilyl)ethane and trifunctional silane with thiourea groups [≡Si(CH3)2NHC(S)·NHC2H5]. It is shown that the increase in relative amount of structuring agent does not cause the increase in the specific surface value and the other parameters of porous structure. It arises from the significant increase in gel formation time in this system. It is found that synthesized xerogels can adsorb Hg2+ ions from the acidified water solutions. In this case in the surface layer formation of complexes of mercury(II) of different composition and with coordination sphere of different nature is possible due to thione-thiol tautomerism characteristic of thiourea group. 相似文献
16.
Sergey Sladkevich Vitaly Gutkin Ovadia Lev Elena A. Legurova Dzhalil F. Khabibulin Martin A. Fedotov Vladimir Uvarov Tatiana A. Tripol’skaya Petr V. Prikhodchenko 《Journal of Sol-Gel Science and Technology》2009,50(2):229-240
Stable, amorphous potassium peroxystannate nanoparticles of controlled average size—in the range 10–100 nm—and of controlled
hydrogen peroxide content—in the range of 19–30 wt%—were synthesized by hydrogen peroxide induced polymerization in water–potassium
hexahydroxostannate solutions. The sol phase and the precipitate were characterized by vibrational spectroscopies, 119Sn NMR, XPS and XRD using crystalline K2Sn(OH)6 and K2Sn(OOH)6 reference materials. This is the first study to show that peroxocoordination induces polymerization of a main group element.
119Sn NMR studies show that peroxotin coordination and polymerization took place already in the hydrogen peroxide–water phase.
The high abundance of peroxotin bonds revealed by 119Sn MAS NMR, vibrational spectroscopy, and XPS suggests that the particles are predominantly made of peroxo bridged tin networks.
Although the particles are highly stable in the dry phase as well as in alcohol solutions and do not lose hydrogen peroxide
upon storage, they release their stored hydrogen peroxide content by exposure to water. 相似文献
17.
Thermal behaviour of nickel amine complexes containing SO4
2−, NO3
−, Cl− and Br− as counter ions and ammonia and ethylenediamine as ligands have been investigated using simultaneous TG/DTA coupled with
mass spectroscopy (TG/DTA–MS). Evolved gas analyses detected various transient intermediates during thermal decomposition.
The nickel ammonium sulphate complex produces NH, N, S, O and N2 species. The nickel ammonium nitrate complex generated fragments like N, N2, NO, O2, N2O, NH2 and NH. The halide complexes produce NH2, NH, N2 and H2 species during decomposition. The ligand ethylenediamine is fragmented as N2/C2H4, NH3 and H2. The residue hexaamminenickel(II) sulphate produces NiO with crystallite size 50 nm. Hexaammine and tris(ethylenediamine)nickel(II)
nitrate produce NiO in the range 25.5 nm and 23 nm, respectively. The halide complexes produce nano sized metallic nickel
(20 nm) as the residue. Among the complexes studied, the nitrate containing complexes undergo simultaneous oxidation and reduction. 相似文献
18.
Alkylation of 8-dimethylamino-1-methylamino-4-nitronaphthalene in the CD3I/KOH/DMSO system afforded a 4-nitro derivative containing the N(CD3)Me group in position 1. Direct proof of the structure of the intramolecular hydrogen bond in solutions of monoprotonated
4-R-1,8-bis(dimethylamino)naphthalenes was obtained for the first time. 1H NMR study revealed that the chelated NH proton is shifted to the N(8) atom for R = NO2 and NH3
+ and to the N(1) atom for R = NH2.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 159–162, January, 2006. 相似文献
19.
A. N. Tishkina A. N. Lukoyanov A. G. Morozov G. K. Fukin K. A. Lyssenko I. L. Fedushkin 《Russian Chemical Bulletin》2009,58(11):2250-2257
The reactions of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-BIAN, 1) with tri-iso-butylaluminum, triethylgallium or trimethylindium give the novel amido-imine complexes (Bui—dpp-BIAN)AlBui
2 (4), (Et—dpp-BIAN)GaEt2 (5), and (Me—dpp-BIAN)InMe2 (6), respectively. The reaction of (dpp-BIAN)AlI(Et2O) (7) with allyl bromide affords analogous chiral amido-imine derivative (All—dpp-BIAN)AlBrI (8). Hydrolysis of 8 affords the amino-imino compound (All—dpp-BIAN)H (9). The new compounds 4–6, 8, and 9 have been characterized by 1H NMR and IR spectroscopy. The molecular structures of 5, 6, and 9 were determined by single crystal X-ray analysis. 相似文献
20.
The electronic structures of amidine CH3C(NH)NH2 and its complex [Pt(NH3)5{CH3C(NH)NH2}]4+ are studied by the semiempirical CNDO method and by the ab initio Hartree-Fock-Roothaan method using the effective core potential
for the platinum atom by the GAUSSIAN-92 program. It is shown that in free amidine the protonation of the NH group is energetically
more profitable than the protonation of the NH2 group. Formation of the amidine-platinum(IV) ion complex is accompanied by a considerable redistribution of electron density
in amidine atoms and bonds. In the above complex, the amidine NH2 group exhibits enhanced protophilic properties.
St. Petersburg State Technological Institute (Technical University). Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 2, pp. 220–224, March–April, 1996.
Translated by I. Izvekova 相似文献