The optimal geometry, IR spectrum and vibration assignment of 4,4＇-dibromodiphenyl ether（BDE-15） in gas phase were calculated via the density functional theory（DFT） at the level of B3LYP/6-3 l＋G（d）. Based on t...The optimal geometry, IR spectrum and vibration assignment of 4,4＇-dibromodiphenyl ether（BDE-15） in gas phase were calculated via the density functional theory（DFT） at the level of B3LYP/6-3 l＋G（d）. Based on the vi- bration assignment, the calculation of vibration frequencies and intensities of 5 main vibration types of BDE-15 in 25 kinds of solvents was carried out by means of a self-consistent reaction field（SCRF） theoretical model at the level of B3LYP/6-31＋G（d） to analyze the solvent effect on the vibration of IR spectrum of BDE-15. To study the solvent ef- fect further, C--O asymmetric stretching vibration fluctuating, which is relatively acute in both vibration frequency and intensity, was selected as the characteristic vibration to establish different linear solvation energy relation（LSER） models for solvent categoring. Solvent parameters（a, /3, ~r＊）, acceptable number（AN） and quantitative structure- activity relationship（QSAR） models were established via chemical quantum parameters of solvent moleculer, which were first been introduced to investigate different solvent-solute interaction mechanisms in alcoholic and non-alcoholic solvents on molecular level. At last, a single solvent molecule was embedded in the framework of po- larizable continuum model（PCM） to validate the effect of hydrogen bonding on solvent-solute interaction in alcohol solvents. The obtained results show that 5 main vibration types of BDE-15 in different solvents have small variation range in frequency and intensity and all the vibration frequencies in solvents are lower than those in gas phase, de- creasing along with the increasing of the dielectric Constant（e） of solvents exponentially. In contrast, all the vibration intensities in solvents are greater than those in gas phase and present positive exponential trend. Twenty-five solvents were divided into two categories（non-alcoholic solvents and alcoholic solvents） by LSER. The CmO asymmetric stretching vibration was mainly regulated by non-specific interaction（dipole-dipole and dipole-induced dipole inter- action） and the combination of non-specific interaction and electronic effect in non-alcoholic solvents and alcoholic solvents, respectively, R2 values of the two QSAR models established for different categories are 0.940 and 0.997, both showing good fitness and the decisive parameters for the two models are/~, a= and aye, EHOMO separately, which reflect that the interaction mechanism is coincide with the conclusion obtained by LSER model. The present of hy- drogen bonding in alcoholic solvents improves the differentiation degree of vibration frequency of the two models with the variance increasing from 0.281 to 0.513 and the intensity from 5.263 to 10.382, which is conducive to the identification of polybrominated diphenyl ether（PBDE） homologues, indicating this research would provide theoreti- cal gist for linking the experimental IR spectrum data with the identification of PBDE homologues.展开更多
Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G+* basis set has been empolyed to study the electronic structure and IR spectrum of Huperzine A. The calculation result showed that the character...Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G+* basis set has been empolyed to study the electronic structure and IR spectrum of Huperzine A. The calculation result showed that the characteristic of the predicted IR bands was in general consistent with the experimental spectrum. 45 vibration modes were assigned clearly from the total of 102 vibration bands. The strongest IR-intensive band corresponds to the stretching vibration of the C O bond of the pyridone ring, and the highest frequency band belongs to the pyridone N H stretch. The investigation showed that the obvious differences between the calculated bands and the experimental spectrum existed at the bands involving the hydrogen atoms of amino and pyridone amide groups, which could form intermolecular hydrogen bond with other Huperzine A in the crystal structure. The hydrogen bonds can not only affect the orientation of these hydrogen atoms, but also can affect the force property of the chemical bond, which can change the vibrational frequencies.展开更多
首次以天然红辉沸石水热合成了 Y 型、P 型分子筛,以 IR 研究了水热合成体系中分子筛结构的演变及晶相分布规律。研究表明,在高 H_2O/Na_2O、低Ca^(2+)/Na^+体系中,主晶相为 Y 型分子筛,在低 H_2O/Na_2O、高 Ca^(2+)/Na^+体系中,主晶相...首次以天然红辉沸石水热合成了 Y 型、P 型分子筛,以 IR 研究了水热合成体系中分子筛结构的演变及晶相分布规律。研究表明,在高 H_2O/Na_2O、低Ca^(2+)/Na^+体系中,主晶相为 Y 型分子筛,在低 H_2O/Na_2O、高 Ca^(2+)/Na^+体系中,主晶相为 P 型分子筛。展开更多
文摘The optimal geometry, IR spectrum and vibration assignment of 4,4＇-dibromodiphenyl ether（BDE-15） in gas phase were calculated via the density functional theory（DFT） at the level of B3LYP/6-3 l＋G（d）. Based on the vi- bration assignment, the calculation of vibration frequencies and intensities of 5 main vibration types of BDE-15 in 25 kinds of solvents was carried out by means of a self-consistent reaction field（SCRF） theoretical model at the level of B3LYP/6-31＋G（d） to analyze the solvent effect on the vibration of IR spectrum of BDE-15. To study the solvent ef- fect further, C--O asymmetric stretching vibration fluctuating, which is relatively acute in both vibration frequency and intensity, was selected as the characteristic vibration to establish different linear solvation energy relation（LSER） models for solvent categoring. Solvent parameters（a, /3, ~r＊）, acceptable number（AN） and quantitative structure- activity relationship（QSAR） models were established via chemical quantum parameters of solvent moleculer, which were first been introduced to investigate different solvent-solute interaction mechanisms in alcoholic and non-alcoholic solvents on molecular level. At last, a single solvent molecule was embedded in the framework of po- larizable continuum model（PCM） to validate the effect of hydrogen bonding on solvent-solute interaction in alcohol solvents. The obtained results show that 5 main vibration types of BDE-15 in different solvents have small variation range in frequency and intensity and all the vibration frequencies in solvents are lower than those in gas phase, de- creasing along with the increasing of the dielectric Constant（e） of solvents exponentially. In contrast, all the vibration intensities in solvents are greater than those in gas phase and present positive exponential trend. Twenty-five solvents were divided into two categories（non-alcoholic solvents and alcoholic solvents） by LSER. The CmO asymmetric stretching vibration was mainly regulated by non-specific interaction（dipole-dipole and dipole-induced dipole inter- action） and the combination of non-specific interaction and electronic effect in non-alcoholic solvents and alcoholic solvents, respectively, R2 values of the two QSAR models established for different categories are 0.940 and 0.997, both showing good fitness and the decisive parameters for the two models are/~, a= and aye, EHOMO separately, which reflect that the interaction mechanism is coincide with the conclusion obtained by LSER model. The present of hy- drogen bonding in alcoholic solvents improves the differentiation degree of vibration frequency of the two models with the variance increasing from 0.281 to 0.513 and the intensity from 5.263 to 10.382, which is conducive to the identification of polybrominated diphenyl ether（PBDE） homologues, indicating this research would provide theoreti- cal gist for linking the experimental IR spectrum data with the identification of PBDE homologues.
文摘Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G+* basis set has been empolyed to study the electronic structure and IR spectrum of Huperzine A. The calculation result showed that the characteristic of the predicted IR bands was in general consistent with the experimental spectrum. 45 vibration modes were assigned clearly from the total of 102 vibration bands. The strongest IR-intensive band corresponds to the stretching vibration of the C O bond of the pyridone ring, and the highest frequency band belongs to the pyridone N H stretch. The investigation showed that the obvious differences between the calculated bands and the experimental spectrum existed at the bands involving the hydrogen atoms of amino and pyridone amide groups, which could form intermolecular hydrogen bond with other Huperzine A in the crystal structure. The hydrogen bonds can not only affect the orientation of these hydrogen atoms, but also can affect the force property of the chemical bond, which can change the vibrational frequencies.
文摘首次以天然红辉沸石水热合成了 Y 型、P 型分子筛,以 IR 研究了水热合成体系中分子筛结构的演变及晶相分布规律。研究表明,在高 H_2O/Na_2O、低Ca^(2+)/Na^+体系中,主晶相为 Y 型分子筛,在低 H_2O/Na_2O、高 Ca^(2+)/Na^+体系中,主晶相为 P 型分子筛。
