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1.
Solid state NMR spectroscopy is inherently sensitive to chemical structure and composition and thus makes an ideal method to probe the heterogeneity of multicomponent polymers. Specifically, NMR spin diffusion experiments can be used to extract reliable information about spatial domain sizes on multiple length scales, provided that magnetization selection of one domain can be achieved. In this paper, we demonstrate the preferential filtering of protons in fluorinated domains during NMR spin diffusion experiments using 1H‐19F heteronuclear dipolar dephasing based on rotational echo double resonance (REDOR) MAS NMR techniques. Three pulse sequence variations are demonstrated based on the different nuclei detected: direct 1H detection, plus both 1H?13C cross polarization and 1H?19F cross polarization detection schemes. This 1H‐19F REDOR‐filtered spin diffusion method was used to measure fluorinated domain sizes for a complex polymer blend. The efficacy of the REDOR‐based spin filter does not rely on spin relaxation behavior or chemical shift differences and thus is applicable for performing NMR spin diffusion experiments in samples where traditional magnetization filters may prove unsuccessful. This REDOR‐filtered NMR spin diffusion method can also be extended to other samples where a heteronuclear spin pair exists that is unique to the domain of interest.  相似文献   

2.
Solid‐state NMR measurements coupled with density functional theory (DFT) calculations demonstrate how hydrogen positions can be refined in a crystalline system. The precision afforded by rotational‐echo double‐resonance (REDOR) NMR to interrogate 13C–1H distances is exploited along with DFT determinations of the 13C tensor of carbonates (CO32?). Nearby 1H nuclei perturb the axial symmetry of the carbonate sites in the hydrated carbonate mineral, hydromagnesite [4 MgCO3?Mg(OH)2?4 H2O]. A match between the calculated structure and solid‐state NMR was found by testing multiple semi‐local and dispersion‐corrected DFT functionals and applying them to optimize atom positions, starting from X‐ray diffraction (XRD)‐determined atomic coordinates. This was validated by comparing calculated to experimental 13C{1H} REDOR and 13C chemical shift anisotropy (CSA) tensor values. The results show that the combination of solid‐state NMR, XRD, and DFT can improve structure refinement for hydrated materials.  相似文献   

3.
The ditopic ligand 1, 2‐bis(benzimidazol‐1‐ylmethyl)benzene (L1) as well as its silver(I) complexes [Ag2L12(CF3CO2)2] ( 1 ) and [Ag2L12](CF3SO3)2 · (L1) · 2H2O · 0.5C2H5OH ( 2 ) were prepared and structures characterized by X‐ray crystallography. The AgI atoms in 1 are trigonally coordinated by two NBIm atoms from the arms of L1 and by one O atom of the anion CF3CO2, while those in 2 are only linearly ligated by NBIm. Different silver salts of CF3CO2 and CF3SO3 lead to different configurations of the dimeric unit [Ag2L12]2+: chair‐form in ( 1 ) but boat‐form in ( 2 ). The discrete molecules in both 1 and 2 are assembled into network structures through face‐to‐face π · · · π stacking and edge‐to‐face C—H · · · π interactions in the crystalline state, as well as N—H · · · O and C—H · · · O hydrogen bonds. Solution 1H NMR studies showed the formation of one sole species in solution or a rapid equilibrium was established on the NMR time scale at room temperature.  相似文献   

4.
Some new N‐4‐Fluorobenzoyl phosphoric triamides with formula 4‐F‐C6H4C(O)N(H)P(O)X2, X = NH‐C(CH3)3 ( 1 ), NH‐CH2‐CH=CH2 ( 2 ), NH‐CH2C6H5 ( 3 ), N(CH3)(C6H5) ( 4 ), NH‐CH(CH3)(C6H5) ( 5 ) were synthesized and characterized by 1H, 13C, 31P NMR, IR and Mass spectroscopy and elemental analysis. The structures of compounds 1 , 3 and 4 were investigated by X‐ray crystallography. The P=O and C=O bonds in these compounds are anti. Compounds 1 and 3 form one dimensional polymeric chain produced by intra‐ and intermolecular ‐P=O···H‐N‐ hydrogen bonds. Compound 4 forms only a centrosymmetric dimer in the crystalline lattice via two equal ‐P=O···H‐N‐ hydrogen bonds. 1H and 13C NMR spectra show two series of signals for the two amine groups in compound 1 . This is also observed for the two α‐methylbenzylamine groups in 5 due to the presence of chiral carbon atom in molecule. 13C NMR spectrum of compound 4 shows that 2J(P,Caliphatic) coupling constant for CH2 group is greater than for CH3 in agreement with our previous study. Mass spectra of compounds 1 ‐ 3 (containing 4‐F‐C6H4C(O)N(H)P(O) moiety) indicate the fragments of amidophosphoric acid and 4‐F‐C6H4CN+ that formed in a pseudo McLafferty rearrangement pathway. Also, the fragments of aliphatic amines have high intensity in mass spectra.  相似文献   

5.
The oxidation of perfluorobutene‐2 (C4F8) initiated by trifluoromethyl hypofluorite (CF3OF) in presence of O2 has been studied at 323.1, 332.6, 342.5, and 352.0 K, using a conventional static system. The initial pressure of CF3OF was varied between 4.8 and 23.6 Torr, that of C4F8 between 48.7 and 302.4 Torr, and that of O2 between 51.5 and 270.4 Torr. Several runs were made in presence of 325.5–451.2 Torr of N2. The main products were COF2, CF3C(O)F, and CF3OC(O)F. Small amounts of compound containing ? CF(CF3)? O? C(O)CF3 group were also formed, as detected by 13C NMR spectroscopy. The oxidation is a homogeneous short‐chain reaction, attaining, at the pressure of O2 used, the pseudo‐zero‐order condition with respect to O2 as reactant. The reaction is independent of the total pressure. Its basic steps are as follows: the thermal generation of CF3O? radicals by the abstraction of fluorine atom of CF3OF by C4F8, the addition of CF3O? to the alkene, the formation of perfluoroalkoxy radicals RO? in presence of O2, and the decomposition of these radicals via the C? C bond scission, giving products containing ? C(O)F end group and reforming RO? and CF3O? radicals. The mechanism consistent with experimental results is postulated. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 532–541, 2003  相似文献   

6.
To enable a comparison between a C—H…X hydrogen bond and a halogen bond, the structures of two fluorous‐substituted pyridinium iodide salts have been determined. 4‐[(2,2‐Difluoroethoxy)methyl]pyridinium iodide, C8H10F2NO+·I, (1), has a –CH2OCH2CF2H substituent at the para position of the pyridinium ring and 4‐[(3‐chloro‐2,2,3,3‐tetrafluoropropoxy)methyl]pyridinium iodide, C9H9ClF4NO+·I, (2), has a –CH2OCH2CF2CF2Cl substituent at the para position of the pyridinium ring. In salt (1), the iodide anion is involved in one N—H…I and three C—H…I hydrogen bonds, which, together with C—H…F hydrogen bonds, link the cations and anions into a three‐dimensional network. For salt (2), the iodide anion is involved in one N—H…I hydrogen bond, two C—H…I hydrogen bonds and one C—Cl…I halogen bond; additional C—H…F and C—F…F interactions link the cations and anions into a three‐dimensional arrangement.  相似文献   

7.
A binary catalyst system of a chiral (R,R)‐SalenCoIII(2,4‐dinitrophenoxy) (salen = N,N‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐diphenylethylenediimine) in conjunction with (4‐dimethylamino)pyridine (DMAP) was developed to generate the copolymerization of carbon dioxide (CO2) and racemic propylene oxide (rac‐PO). The influence of the molar ratio of catalyst components, the operating temperature, and reaction pressure on the yield as well as the molecular weight of polycarbonate were systematically investigated. High yield of turnover frequency (TOF) 501.2 h?1 and high molecular weight of 70,400 were achieved at an appropriate combination of all variables. The structures of as‐prepared products were characterized by the IR, 1H NMR, 13C NMR measurements. The linear carbonate linkage, highly regionselectivity and almost 100% carbonate content of the resulting polycarbonate were obtained with the help of these effective catalyst systems under facile conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5050–5056, 2007  相似文献   

8.
Employing a multitude of modern solid state NMR techniques including 13C{15N}REDOR NMR, 1H–13C CP NMR, 11B MQMAS NMR spectroscopic experiments, the structural organization of Si2B2N5C4 ceramic has been studied. The experiments were executed on double isotope enriched (13C, 15N) and natural isotope abundance Si2B2N5C4 ceramics. The materials were synthesized by aminolysis and subsequent pyrolysis of intermediate pre‐ceramic polymers that were obtained from the single source precursor TSDE, 1‐(trichlorosilyl)‐1‐(dichloroboryl)ethane (Cl3Si–CH(CH3)–BCl2). The result of the 13C{15N} REDOR NMR spectroscopic experiment shows that carbon atoms are incorporated into the network by bridging to nitrogen, which already occurs during the polymerization step. Furthermore, the combined results of 11B NMR and 11B MQMAS NMR indicate that boron atoms may also be connected to carbon in addition to nitrogen.  相似文献   

9.
Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether‐containing benzoxazines. In this study, we report a facile, deprotection‐free preparation of a propargyl ether‐containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH‐containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high‐resolution mass spectrum, 1H, 13C, 1H‐1H, 1H‐13C nuclear magnetic resonance (NMR) spectra, and X‐ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring‐opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structure–property relationship of the resulting homopolymers and copolymers are discussed. The Tg of homopolymer of (2) is 208 °C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/°C, and Td 5% (N2) is 393 °C, respectively, which are higher than those of the homopolymer of (1) . Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

10.
The extremely labile perfluoro‐2‐arsapropene F3CAsCF2 ( 1 ) has been generated by an improved pyrolysis process of Me3SnAs(CF3)2 and found to be stabilized by the presence of hexamethyldisiloxane and tert‐butylphosphaethyne, thus allowing (i) reactivity studies with alkyne derivatives like tBuCP, (iPr)2NCP, MeCCN(iPr)2, HCCOEt and (ii) a full NMR investigation of 1 (19F, 13C). Due to the instability of 1 and some of the products, the [2+2]‐cycloaddition reactions gave the expected arsaphospha‐ and arsa‐cyclobutene derivatives, respectively, in moderate to good yields, but in some cases contaminated with side and/or decomposition products. Unequivocal characterization of the novel compounds was accomplished by spectroscopic in‐ vestigations (1H, 13C, 19F, 31P NMR, IR, MS) supported by comparison with the data of the more stable phosphorus analogues. An interesting isomerization was observed for the 2‐dialkylamino‐4,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐3‐phospha‐2‐cyclobutenes yielding the more stable 3‐dialkylamino‐2,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐2‐phospha‐3‐cyclobutenes. Quantum chemical calculations [B3LYP/6‐311+ G(d,p)] of HAsCH2, F3CAsCF2, and F3CPCF2 were carried out to compare the length of the AsC double bond with the literature data and to elucidate substituent effects on its electronic structure. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:406–419, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20118  相似文献   

11.
The polyaddition of 1,4‐bis[(3‐ethyl‐3‐oxetanyl)methoxymethyl]benzene with 2,2′‐bis[(4‐chloroformyl)oxyphenyl]propane was examined with quaternary onium salts as catalysts. When the polyaddition was carried out with tetrabutylphosphonium bromide in chlorobenzene at 120 °C for 24 h, the corresponding poly(alkyl aryl carbonate) with a high molecular weight (number‐average molecular weight = 16,700) was obtained in an almost quantitative yield. It was found from the 1H NMR and 13C NMR spectra of the obtained polymer that the addition reaction proceeded without any side reactions, providing the polycarbonate with pendant chloromethyl groups in the side chain. The polyaddition of bis{[3‐(3‐ethyloxetanyl)]methyl}terephthalate also proceeded smoothly and gave the corresponding polycarbonate with high molecular weight in a good yield. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2304–2311, 2003  相似文献   

12.
Novel fully lower‐rim, carbonate‐bridged calix[8]arene derivatives were successfully synthesized in high yield by the condensation of p‐alkyl substituted calix[8]arenes with triphosgene. Different bases and catalysts were used for the preparation depending on the p‐alkyl substituted groups of the calix[8]arenes. The conformational features of the derivatives were examined by 1H NMR analysis. Thermosetting formulations were prepared from a mixture of bisphenol A polycarbonate with calix[8]arene carbonate derivatives using sodium benzoate as a catalyst. Their crosslinking behaviors were studied using differential thermal/thermogravimetric analysis. No glass‐transition temperatures were observed after annealing at 280–300 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1149–1155, 2001  相似文献   

13.
Bis‐benzimidazolium salt 1 was prepared via a series of reactions using 2,2′‐diphenol as starting material. Compound 2 was afforded through the intramolecular C? C coupling reaction of 1 under the catalysis of Pd(OAc)2. The structure of 2 is characterized through X‐ray diffraction analyses, 1H NMR and 13C NMR. In 2 , two boat‐like seven‐membered rings are contained, where the C? C bond distance newly formed is 1.461(5) Å, and it is between regular C? C single bond (1.54 Å) and C?C double bond (1.34 Å). This shows that new C? C bond has partial double‐bond character. In the crystal packing of 2 , the 2D supramolecular layers are formed via C? H···F hydrogen bond.  相似文献   

14.
The quadruply bonded Mo24+ complex Mo2(DAniF)3(OOCC6F5) ( 1 ) [DAniF = N,N′‐bis(4‐methoxyphenyl)formamidinate] was synthesized. The solvate Mo2(DAniF)3(OOCC6F5) · (C6H6) ( 2 ) and co‐crystal Mo2(DAniF)3(OOCC6F5) · (C10H8) ( 3 ) complexes were obtained by self‐assembly of crystals of 1 with benzene and naphthalin, respectively. Compounds 1 , 2 , and 3 were structurally characterized by single‐crystal X‐ray diffraction. In monomer 1 , the Mo–Mo bond length of 2.0874(6) Å is typical for dimolybdenum quadruple bonds. The solvate complex 2 was stabilized by weak π–π stacking interactions between the benzene molecule and the pentafluorophenyl ring (as indicated by a center‐to‐center distance of 3.838(10) Å and a center‐to‐plane distance of 3.712(4) Å between phenyl and pentafluorophenyl ring) and intermolecular C–H ··· F–C interactions (the shortest F ··· H distance is 2.560(2) Å). In complex 3 , a one‐dimensional chain was formed by C–H ··· F–C interactions between the hydrogen atoms in naphthalin and the fluorine atoms in the monomer (H ··· F distances of 2.582(2) Å). Information on the structures in solution of the three crystals was obtained by 1H NMR spectroscopy.  相似文献   

15.
A new six‐membered cyclic carbonate monomer, 5‐benzyloxy‐trimethylene carbonate, was synthesized from 2‐benzyloxy‐1,3‐propanediol, and the corresponding polycarbonate, poly(5‐benzyloxy‐trimethylene carbonate) (PBTMC), was further synthesized by ring‐opening polymerization in bulk at 150 °C using aluminum isobutoxide [Al(OiBu)3], aluminum isopropoxide, or stannous octanoate as an initiator. The results showed that a higher molecular weight polycarbonate could be obtained in the case of Al(OiBu)3. The protecting benzyl group was removed subsequently by catalytic hydrogenation to give a polycarbonate containing a pendant hydroxyl group (PHTMC). The polycarbonates obtained were characterized by Fourier transform infrared spectroscopy, 1H NMR,13C NMR, gel permeation chromatography, and DSC. NMR results of PBTMC offered no evidence for decarboxylation occurring during the propagation. The pendant hydroxyl group in PHTMC resulted in an enhancement of the hydrophilicity of the polycarbonate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 70–75, 2002  相似文献   

16.
The NCOCH2(CF2)6CH2OCN fluoromethylene cyanate ester monomer and resin are synthesized and characterized. The monomer is prepared by a large‐scale bench‐top synthesis, characterized by differential scanning calorimetry, infrared, 1H‐, 13C‐, 15N‐, and 19F‐NMR spectroscopies and analyzed for catalytically active impurities. Conversion of the monomer to prepolymer and cured resin is characterized by IR and NMR spectroscopies and kinetically analyzed. Resin properties characterization includes thermal, tensile, dynamic mechanical, dielectric, refractive index, thermodielectric and thermogravimetric stabilities, and water absorption. Relevant property comparisons with the commercial AroCy F cyanate ester resin (6F bisphenol A dycyanate) and a Jeffamine‐bisphenol diglycidyl ether epoxy are made. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 135–150, 1999  相似文献   

17.
王飞  胡金波 《中国化学》2009,27(1):93-98
三氟甲磺酸被发现能够高效地活化(SP3)碳-氟键。因此,在其催化作用下,室温时含三氟甲基的芳香化合物与苯反应得到二苯甲酮类化合物。在同样的Brønsted 酸催化下,其中一些含三氟甲基的芳香化合物亦可发生分子内的芳基化反应,而此时分子间的芳基化受抑制。强的氢氟间的相互作用或氢键作用,被认为对该Brønsted 酸参与碳氟键活化的反应起了重要作用。  相似文献   

18.
The X‐ray crystal structures of the polyfluorinated complexes [5,5′‐bis(HCF2CF2CF2CF2CH2OCH2)‐2,2′‐bpy]MI2 ( 55‐8F‐PtI 2 and 55‐8F‐PdI 2 where M = Pt and Pd, respectively) were obtained. These two structures are found to show not only two different types of intramolecular, six‐membered cyclic C–H···F–C interactions (F2C–H···F–C and HC–H···F–C) as important structural features but also alternating fluorinated and non‐fluorinated layers. The F2C–H···F–C interactions, which are close to the metal core, are much better structurally characterized in this type of complexes with fluorous ponytails at the 5,5′ positions than those previously reported at the 4,4′ positions. The molecular planes of (bpy)MI2 are extended by self‐matching, using two C–H···I hydrogen bonds and one C–H···F–C blue‐shifting hydrogen bond. The F2C–H···F–C hydrogen bonds interact at the supramolecular level such that one polyfluorinated ponytail of the title compounds is transoid without an intramolecular C–H···F–C interaction, while the other polyfluorinated ponytail is cisoid with an intramolecular C–H···F–C interaction. Why one ponytail is cisoidal while the other is transoidal will be explained. Furthermore, the second type of C–H···F–C interactions involving the methylene H atom has been identified for the first time. In addition, these two metal structures are studied by density functional theory (DFT).  相似文献   

19.
Five mono‐nuclear silver (I) complexes with 6,7‐dicyanodipyridoquinoxaline ligand, namely {[Ag(DPEphos)(dicnq)]NO3}2 · CH3OH ( 1 ), [Ag(DPEphos)(dicnq)]BF4 · CH3OH ( 2 ), [Ag(XANTphos)(dicnq)]CF3SO3 ( 3 ), {[Ag(XANTphos)(dicnq)]NO3}2 ( 4 ), and [Ag(XANTphos)(dicnq)]ClO4 · CH2Cl2 ( 5 ) {DPEphos = bis[2‐(diphenylphosphanyl)phenyl]ether, dicnq = 6,7‐dicyanodipyridoquinoxaline, XANTphos = 9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)xanthene} were characterized by X‐ray diffraction, IR, 1H NMR, 31P NMR, fluorescence spectra, and terahertz time‐domain spectra (THz‐TDS). In the five complexes the AgI, which is coordinated by two kinds of chelating ligands, adopts four‐coordinate modes to generate mono‐nuclear structures. The C–H ··· π interactions lead to formation of a 1D infinite chain for complexes 2 and 3 . The crystal packing of complexes 1 and 5 reveal that they form 3D supermolecular network by several pairs of C–H ··· π interactions. The emissions of these complexes are attributed to ligands‐centered [π–π*] transition based on both of the P‐donor and N‐donor ligands.  相似文献   

20.
The crystal structures of [(Z)‐2‐methyl­but‐1‐en‐1‐yl]­[4‐(tri­fluoro­methyl)­phenyl]­iodo­nium tri­fluoro­methane­sulfonate, C12H13F3I+·CF3O3S?, (I), (3,5‐di­chloro­phenyl)­[(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium tri­fluoro­methane­sulfonate, C11H12­Cl2I+·CF3O3S?, (II), and bis{[3,5‐bis­(tri­fluoro­methyl)­phenyl][(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium} bis­(tri­fluoro­methane­sulfonate) di­chloro­methane solvate, 2C13H12F6I+·­2CF3­O3S?·CH2Cl2, (III), are described. Neither simple acyclic β,β‐di­alkyl‐substituted alkenyl­(aryl)­idonium salts nor a series containing electron‐deficient aryl rings have been described prior to this work. Compounds (I)–(III) were found to have distorted square‐planar geometries, with each I atom interacting with two tri­fluoro­methane­sulfonate counter‐ions.  相似文献   

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