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981.
982.
983.
984.
The kinetics of hydrogen exchange in molecular systems with H-bonds has been studied by means of kinetic IR spectroscopy and low-temperature NMR spectroscopy. The experimental values of the rate constants and activation energies for molecules capable of forming H-bonds as both proton donors and proton acceptor are collected and analyzed from the point of view of the influence of H-bond formation ability of the molecules-partners. The evidence available testifies to a molecular mechanism of the H-exchange reactions in inert solvents and in the gas phase via the formation of cyclic bimolecular intermediates. The different mechanisms and the structure of intermediate complex of molecular H-exchange process in inert media are discussed and the possible paths of experimental elucidation of reaction mechanism are offered. 相似文献
985.
A. A. Hasanein G. M. El-Subruiti G. O. Younes M. H. Srour 《Journal of solution chemistry》2004,33(12):1481-1499
The electronic absorption spectra of 2-aminopyrimidine (compound I), 2-amino-4-methylpyrimidine (compound II), 2-amino-4,6-dimethylpyrimidine (compound III), 2-amino-4,6-dimethoxypyrimidine (compound IV), 4-amino-2,6-dimethylpyrimidine (compound V), and 4,5-diamopyrimidine (compound VI) have been measured in water and in a series of different organic solvents. The solvent effects on the spectra are discussed and the solvent induced spectral shifts are analyzed in terms of different solute–solvent interaction mechanisms, using the multiple linear regression technique. 相似文献
986.
A new scheme has been developed for determining the parameters of the local one-electron potential in molecules and solids. The scheme is based on interpretation of the experimental X-ray absorption near edge struucture. The scheme is an extension of the method for solving the inverse problem of XANES theory suggested by one of the authors. In this scheme, oscillator strengths and maximum heights are considered along with the energy and half-width of spectral maxima. The scheme is used for determining the intraatomic potential in the nitrogen molecule.Original Russian Text Copyright © 2004 by Yu. F. Migal and O. M. Kholodova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 986–989, November–December, 2004. 相似文献
987.
Organic Crystals with Near‐Infrared Amplified Spontaneous Emissions Based on 2′‐Hydroxychalcone Derivatives: Subtle Structure Modification but Great Property Change 下载免费PDF全文
Xiao Cheng Kai Wang Shuo Huang Dr. Houyu Zhang Prof. Dr. Hongyu Zhang Prof. Dr. Yue Wang 《Angewandte Chemie (International ed. in English)》2015,54(29):8369-8373
A series of highly efficient deep red to near‐infrared (NIR) emissive organic crystals 1 – 3 based on the structurally simple 2′‐hydroxychalcone derivatives were synthesized through a simple one‐step condensation reaction. Crystal 1 displays the highest quantum yield (Φf) of 0.32 among the reported organic single crystals with an emission maximum (λem) over 710 nm. Comparison between the bright emissive crystals 1 – 3 and the nearly nonluminous compounds 4 – 7 clearly gives evidence that a subtle structure modification can arouse great property changes, which is instructive in designing new high‐efficiency organic luminescent materials. Notably, crystals 1 – 3 exhibit amplified spontaneous emissions (ASE) with extremely low thresholds. Thus, organic deep red to NIR emissive crystals with very high Φf have been obtained and are found to display the first example of NIR fluorescent crystal ASE. 相似文献
988.
利用稳态线性红外光谱和飞秒泵浦-探测红外光谱技术, 研究了在乙腈(MeCN)、丙酮(AC)、四氢呋喃(THF)和二甲基亚砜(DMSO)溶剂中乙二醇(EG)的结构和羟基(―OH)伸缩振动动力学. 结果表明, 乙二醇的―OH伸缩振动的频率位置、峰宽以及振动弛豫动力学都表现出强烈的溶剂依赖性. 乙二醇溶液中至少存在两种形式的分子间氢键, 一种是溶质-溶剂团簇的分子间氢键, 另一种是溶质-溶质团簇的分子间氢键. 量子化学计算预测的―OH伸缩振动频率的溶剂依赖性与我们的红外光谱实验观测结果一致. 进一步, 我们发现在乙腈中参与形成溶质-溶剂团簇氢键的乙二醇―OH伸缩振动具有最慢的弛豫动力学, 丙酮和四氢呋喃次之, 而最快的弛豫动力学过程发生在二甲基亚砜中. 在每一溶剂条件下, 乙二醇/乙二醇溶质团簇中―OH伸缩振动弛豫都更快一些. 本文结果有助于认识在溶质-溶质、溶质-溶剂分子团簇共存的体系中不同分子间氢键的结构动力学特性. 相似文献
989.
FCC汽油中含硫化合物在Ce交换的Y型分子筛上的吸附 总被引:14,自引:0,他引:14
研究了NaY分子筛在与硝酸铈溶液进行液相离子交换前后对含有大量芳烃和烯烃的FCC汽油的吸附脱硫. 结果表明,在室温和常压下,以离子交换方式将Ce3+引入到Y分子筛中后,分子筛吸附剂对FCC汽油的脱硫选择性明显提高,并且脱硫选择性随分子筛中Ce3+含量的增多而提高. 噻吩吸附的红外光谱表明,在Ce3+改性后的分子筛吸附剂上存在着噻吩分子直接以硫原子与吸附剂相互作用的吸附模式,这种不同于π络合的吸附方式可能不易受FCC汽油中竞争分子的影响,因此分子筛表现出较高的吸附脱硫选择性. 相似文献
990.
This paper presents the investigation results of the polarized IR spectra of 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde crystals measured at 293 and 77 K. Analysis of the results concerned the linear dichroic, H/D isotopic and temperature effects observed in the spectra of the hydrogen and deuterium bond at the frequency ranges of the νO–H and the νO–D bands, respectively. The main spectral properties of the crystals were interpreted in terms of the “strong-coupling” theory on the basis of the hydrogen bond dimer model. The spectra revealed that the strongest vibrational exciton coupling involved the closely-spaced hydrogen bonds, each belonging to a different chain of associated molecules. The reason for two different crystalline systems, are characterized by almost identical νO–H and νO–D band shapes, is explained. It was proved that a random distribution of the protons and deuterons took place in the lattices of the isotopically diluted crystals. 相似文献