首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Experimental data on the synthesis and spectral properties (UV, IRFourier, xray photoelectronic, and luminescence spectra) of the sulfonamide derivative of benzocoumarin in an isopropanol solution and in a film applied by thermal vacuum deposition (TVD film) are reported. The use of TVD films of the investigated substance as electroluminophors is shown to be promising.  相似文献   

2.
Spectral manifestations of protolytic forms of 1aza2methyl6aminopyrene in ethanol and aqueous solutions are investigated. The ionization constants of the protolytic forms are determined. The generation properties and photostability of a neutral molecule and a cation in excitation by an excimer XeCl laser are studied.  相似文献   

3.
《光谱学快报》2013,46(6):553-564
Abstract

The cis stereochemistry of 6‐(4‐methoxy‐phenyl)‐1,5,7a‐triphenyl‐tetrahydro‐imidazo[1,5‐b][1,2,4]oxadiazol‐2‐one was studied by use of a PM3 semi‐empirical quantum mechanical model, and x‐ray crystallographic analysis. It crystallizes in the monoclinic space group P2 1 /n with a = 10.812(1) Å, b = 16.464(2) Å, c = 13.379(1) Å, α = 90.00°, β = 98.39(1)°, γ = 90.00°, V = 2356.07(4) Å3, Z = 4, D calc = 1.3067 g cm?3, F(0 0 0) = 976.41, and μ = 0.086 mm?1. The structure was solved by direct methods and refined to R = 0.066 for 1257 independent reflections [I > 4σ (I)]. The results from x‐ray diffraction were seen to be generally consistent with the results from previously reported spectroscopic investigations, beside theoretical calculations, except for conformations of five‐membered fused heterocycles. Two inter‐ and intramolecular weak interactions in addition to carbon atoms (C1 and C3) with different chiralities were found in the structure. The conformational study was performed by randomly scanning the potential energy surface belonging to the title compound with respect to selected torsion angles.  相似文献   

4.
《光谱学快报》2013,46(4-5):557-567
Abstract

The synthesis of 2‐(2‐nitrophenyl)‐1H‐benzimidazole (1), 1‐benzoyl‐2‐(2‐nitrophenyl)‐1H ‐benzimidazole (2), and 1‐acetyl‐2‐(2‐nitrophenyl)‐1H‐benzimidazole (3) is reported. Stable radical anions (1 ·?, 2 ·?, and 3 ·?) were generated by chemical reduction in DMSO and studied by ESR spectroscopy. The interpretation of the ESR spectra was done by means of computational simulation process. Hyperfine coupling constants were assigned by comparison with related compounds, and on the basis of calculation based on SCF INDO MO method in the unrestricted Hartree–Fock scheme.  相似文献   

5.
With the availability of the first generation of X-ray free electron lasers, pump-probe measurements with femtosecond resolution and high brilliance are now possible. For condensed matter systems, a wealth of modes in the mid-infrared (MIR) and terahertz (THz) regime determine the physics such that targeted excitation with ultrashort pulses at long wavelength becomes an important tool. We will briefly discuss the methodology of pump-probe experiments at the Linac Coherent Light Source (LCLS) and then review methods of generation of intense THz and MIR pulses. This is followed with recent examples from atomic and condensed matter physics at LCLS, and we conclude with an outlook of future developments in this field.  相似文献   

6.
《光谱学快报》2013,46(1-2):151-165
A novel polymer, poly(2‐methyl‐1‐naphthylamine), which was synthesized electrochemically at various temperatures from a solution containing 2‐methyl‐1‐naphthylamine, acetic acid and sodium acetate, was characterized by IR spectroscopy. The structural conclusions were based on comparisons of polymer spectra with the IR‐spectrum of the monomer, 2‐methyl‐1‐naphthylamine. IR spectroscopy indicates that the electropolymerization proceeds via the –NH2 groups and that the poly(2‐methyl‐1‐naphthylamine) structure consists of imine (–N?C) and amine (–NH–C) links between naphthalene rings as well as a free methyl groups in the chains. An analysis of the “substitution pattern” region in the polymer's spectra suggests that the polymer molecules were formed via mixed N–C(4), N–C(5) and N–C(7) linkages between repeated units. The ratio of between the 1645 and 1620 cm? 1 peak areas decreases with increased temperature during synthesis, indicating that 25°C is the best temperature to obtain higher molecular weights.  相似文献   

7.
Azetidin‐2‐ones, commonly known as β‐lactams, constitute a biologically important class of compound. Treatment of azetidin‐2‐ones with alkali is known to form diverse types of compounds depending on the stability of the ring. In many cases, the ring is retained in the product at the cost of transformation of substituents. Spectroscopy is the most important tool to characterize the organic compounds. However, in some cases the structures of the products are so closely related that simple IR, 1H NMR, and 13C NMR spectra do not lead to unambiguous structure elucidation. This article reports a novel application of 1H‐13C COSY NMR and mass spectroscopy in determining unequivocally an azetidin‐2‐one ring structure instead of a chroman‐2‐one ring structure for the product obtained by treatment of 1‐benzhydryl‐3,3‐bis(4‐methylphenyl)‐4‐[2‐(o‐dip‐tolylacyl)hydroxyphenyl]‐2‐azetidinone with ethanolic sodium hydroxide at room temperature.  相似文献   

8.
《光谱学快报》2013,46(4-5):487-496
Abstract

Inverse secondary kinetic isotope effects are determined for the dimerization of all‐cis‐cyclononatetraenyl radical, 1, to its corresponding dimer, all‐cis‐9,9′‐bicyclonona‐1,3,5,7‐tetraene, 2, (step 1, k H/k D=0.5), and cyclization of the latter to 9,9′‐bisbicyclo[4.3.0]cyclonona‐2,4,7‐triene, 3 (step 2, k H/k D=0.75). These results are obtained by comparison of 1H‐ and 2D‐NMR spectra of 3 and employment of a simple statistical method for acquiring kinetic data. This new strategy appears superior to conventional methods in being fast, simple, and less expensive.  相似文献   

9.
Tetrakis‐(4‐chlorophenylthio)‐butatriene (3a) and tetrakis‐(tert‐butylthio)‐butatriene (3b) were synthesized, and their crystal structures were determined. The compound 3a is monoclinic, space group P21/c, a=6.9785(8), b=8.6803(9), c=22.884(2) Å, β=93.887(6)o, V=1383.0(3) Å3, Z=2. The compound 3b is monoclinic, space group P21/n, a=11.0615(6), b=10.8507(4), c=11.2717(6) Å, β =116.427(2)o, V=1211.5(1) Å3, Z=4. The title compounds 3a and 3b reside on an inversion center so that only half of the molecule is crystallographically unique. Both compounds are not planar. The crystal structures of 3a and 3b have cumulated double bonds. The C7–C8–C8i and C5–C6–C6i angles that show the linearity in both structures, respectively, are 176.4(3)° in 3a and 175.6(2)° in 3b.  相似文献   

10.
An amorphous acrylic acid (AA) polymer coating was generated on TiO2 nanoparticles through pulse radio frequency (RF) plasma polymerization. The AA plasma synthesis mechanism was studied by its optical emission spectrum. The chemical structures of AA–plasma‐polymer were carefully investigated by Fourier transform infrared spectroscopy (FTIR). The dispersion behaviors of AA‐coated and uncoated TiO2 nanoparticles in glycol solution were characterized by ultraviolet absorbency and particle size distribution measurements. The results showed that the aggregation of TiO2 nanoparticles in glycol solution was effectively lowered and the dispersion was improved a lot after AA–plasma‐polymer coating. The pulse plasma coating parameters played an important role in the dispersion enhancement of TiO2 nanoparticles. By properly regulating the pulse discharge parameters, the system could gain the highest radical–monomer reactions rate, the most compatible functional groups on the nanoparticles, and the best dispersion in the background media.  相似文献   

11.
《光谱学快报》2013,46(5):437-456
Abstract

The structures of new isomeric 2‐alkoxycarbonylalkylthio‐ and 2‐alkoxy‐ carbonylalkylthio‐1‐alkoxycarbonylalkyl‐6‐aminouracils (121) have been established on the basis of the 1H NMR and 13C NMR spectroscopic data. The 1H NMR and 13C NMR spectra of 121 have been fully assigned by a combination of two‐dimensional experiments [heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond correlation (HMBC)]. The 13C NMR spectra have been shown to be able to differentiate between isomers.  相似文献   

12.
《光谱学快报》2013,46(6):607-618
Abstract

The enolisation tendencies of 1‐(o‐substituted phenyl)barbituric and ‐2‐thiobarbituric acid derivatives have been studied by observing the behaviour of the compounds in different solvents by 1H and 13C NMR. It has been found that the enolisation tendencies of the thiobarbituric acid derivatives observed in polar solvents are greater than those of the barbituric acid derivatives. The ratio of keto–enol tautomers of thiobarbituric acid derivatives in DMSO and in DMF has been calculated.  相似文献   

13.
The intramolecular hydrogen bond in steroid 5hydroxy6ketones and 5hydroxy6ketoximes of the stigmastane series has been investigated by the method of IR spectroscopy. It is shown that 5hydroxy groups in cisA/Bsteroids are linked by the intramolecular hydrogen bond with polar substituents at C3 and C6. These hydrogen bonds are lacking in corresponding transA/Bsteroids. According to the IR spectra, intramolecular associates of polymer type are formed in 5hydroxy6hydroxyminosteroids.  相似文献   

14.
Using the methods of spectrophotometry, luminescent analysis, and fluorescent probes, we have investigated the structural changes in bull serum albumin (BSA) molecules induced by the action of vacuum UV (VUV) radiation ( = 131161 nm, dose — 6300 kJ/m2). It has been found that the change in the spectralfluorescent properties of BSA molecules after irradiation under the conditions of different microsurroundings is caused by the unrolling of the protein globule due to the weakening and rupture of weak intramolecular bonds as well as by the photomodification of the aromatic amino acid residues in the composition of the protein macromolecule. A scheme of the phototransformation processes in the BSA molecules under the action of vacuum ultraviolet has been drawn. In accordance with this scheme the VUV light in the region of absorption of peptide bonds of protein molecules induces a disturbance in their thirdorder structure, which leads to a modification of the state of aromatic amino acid residues and a change in the functional properties of protein macromolecules.  相似文献   

15.
Abstract

Intercalated polymer/clay nanocomposites were prepared using a polystyrene‐b‐poly(ethylene‐r‐butylene)‐b‐polystyrene (SEBS) cylindrical triblock copolymer. Dynamic rheological measurements, x‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetry analysis (TGA) were conducted to investigate the internal structure and physical and phase characteristics of the nanocomposites. The XRD data confirmed that the interlayer distance between the anisotropic silicates increased due to the intercalation of SEBS into the clay interlayers. As the clay loading increased, the onset points of the order–disorder transition (ODT) and order–order transition (OOT) were found to decrease, whereas the thermal decomposition temperatures, monitored by TGA, increased with the clay loading.  相似文献   

16.
Different intermolecular compounds of 6,6'dimethyl2,3,4,5,6,7hexahydrobenzo[b]furan3,4dione have been investigated by IR spectroscopy and xray structural analysis methods. The relation between changes in the characteristic absorption bands of CH2, CH3, C=O, and C—O—C groups and the properties of the medium surrounding the molecule is established. Crystals of monoclinic syngony, of space group P21/n, are formed from a chloroformhexane mixture in crystallization. In the crystalline structure, shortened intermolecular contacts between the atoms of hydrogen of the CH3 and CH2 groups of cyclohexane cycles and the oxygen atom of the furan cycle, and also between the atoms of hydrogen of the CH2 and CH3 groups of both cycles and the oxygen of the cyclohexane cycle are revealed.  相似文献   

17.
《光谱学快报》2013,46(5-6):537-550
The vibrational frequencies of N‐acetyl‐L‐alanine (NAAL), its potassium salt (NAALK) and its free anionic form (NAAL?) are calculated using density functional theory (B3LYP) combined with the 6‐311 + + G(d,p) basis set. The experimental Raman spectrum of solid NAALK and the scaling factors for calculated values are discussed as well. The three species are characterized by intramolecular NH…O hydrogen bonds leading to the formation of a five‐membered ring. As indicated by the intramolecular (N)H…O distances and by the ν(NH) frequencies, the strength of the intramolecular hydrogen bond is ordered as follows: NAAL? < NAALK < NAAL?. Owing to their difference in the coupling with other vibrational modes, the in‐plane and out‐of‐plane vibrations do not reflect the strength of the hydrogen bond.  相似文献   

18.
Using methods of emission spectroscopy, we have determined the gaskinetic temperature fields of planar highfrequency capacitive discharge plasma in N2/CO2/He gas mixtures depending on the excitation frequency, discharge current, pressure, and chemical composition of the mixture. It is shown that the dominant contribution to the neutral component heating in the center of the discharge chamber is made by the processes of VT relaxation of vibrationally excited molecules N2(X 1, V) and CO2(X 1, V), whereas in the zones near the electrodes an important role in the heating is played, along with the VT relaxation of the N2(X 1, V) and CO2(X 1, V) molecules, by the processes of deactivation of the metastable states A 3 of the N2 molecule.  相似文献   

19.
On the basis of investigation of the absorption and luminescence spectra of 1,1dioctadecyl3,3,3'3'tetramethylindodicarbocyanineperchlorate (D307) molecules and their nonamphiphilic analog in binary solutions of dimethylformamide and water of different composition, a mechanism underlying the quenching luminescence of the D307 molecules has been established which is related to the formation of nonluminescent associates. It is shown that the formation of the micelles of sodium dodecylsulfate (SDS) in a binary solution with 99% content of water destroys the associates, the D307 molecules are captured by the micelles, and their mobility in the micelles is limited.  相似文献   

20.
四丁基溴化铵(TBAB)半笼型水合物在二氧化碳(CO2)捕集和封存技术中具有巨大的发展与应用潜力。由于晶体结构的复杂性,TBAB半笼型水合物的动力学过程尚未得到充分的研究。为了解TBAB半笼型水合物在储气方面的动力学特性,实验采用原位激光拉曼技术和多晶粉末X射线衍射仪(PXRD)对nCO2·TBAB·26H2O和nCO2·TBAB·38H2O水合物的光谱特征进行了鉴别与分析,利用原位激光拉曼技术考察了CO2分子分别进入2种晶体结构的动力学过程。研究结果表明,2种晶体结构的拉曼光谱具有较高的相似性,值得注意的是nCO2·TBAB·26H2O中位于1 309.5和1 326.9 cm-1的拉曼峰为TBA+阳离子中C-C键的变形振动峰,在nCO2·TBAB·38H2O水合物中峰基本不发生改变,但半峰宽降低,峰形也变得相对清晰;同时,nCO2·TBAB·26H2O中位于1 446.6和1 458 cm-1的拉曼峰为TBA+阳离子中C-H键的剪切振动峰,在nCO2·TBAB·38H2O水合物中分别向左、右两边发生了位移,峰形的重叠度也随之下降。依据上述2处拉曼光谱特征可以对2种晶体结构进行辨别。通过PXRD图谱可以发现2种晶体结构的衍射图谱存在着比较明显的差距。nCO2·TBAB·26H2O晶体属于四方晶系,空间群(P4/m),而nCO2·TBAB·38H2O属于正交晶系,空间群(Pmma)。图谱中2θ=8.406°和10.941°分别为nCO2·TBAB·38H2O的(200)和(220)晶面的特征峰,而2θ=5.976°和6.969°分别为nCO2·TBAB·26H2O的(012)和(003)晶面特征峰,可以用来判别样品中水合物的晶体结构。在原位拉曼测量过程中,nCO2·TBAB·26H2O和nCO2·TBAB·38H2O分别在已经合成好的TBAB·26H2O和TBAB·38H2O水合物表面形成。在276 K,2 MPa条件下,气相中的CO2分子分别进入2种晶体结构中用于储气的512笼形结构,在1 275.4和1 379.3 cm-1处形成特征峰并逐渐增长。实验以2种TBAB水合物位于1 110.3 cm-1的拉曼峰作为参考,比较了CO2在水合物中的增长速率。研究发现在反应初期的75 min内CO2在2种水合物中的含量基本保持线性增长且上升速率的差别不大。由于测量点位于水合物表面,受气体在水合物中扩散的阻力较小同时2种TBAB水合物均采用512笼形结构储气导致了储气速率相近。以上的微观晶体结构研究结果对TBAB水合物法捕集和封存CO2技术应用具有重要的意义。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号