Density functional theory (DFT) calculations on a double hydrogen-bonded dimer of o-hydroxybenzoic acid were carried out at the B3LYP/6-31G* level. The optimized geometry of the dimer closely resembles that of the c...Density functional theory (DFT) calculations on a double hydrogen-bonded dimer of o-hydroxybenzoic acid were carried out at the B3LYP/6-31G* level. The optimized geometry of the dimer closely resembles that of the crystal. The calculated results show that the total energy of the dimer is much lower than the sum energies of the two monomers, and the average strength of the double hydrogen bonds is about 38.37 kJ/mol. In order to probe the origin of the interactions in the dimer, natural bond orbital analyses were performed. The thermodynamic properties of the title compound at different temperatures have also been calculated on the basis of vibrational analyses and ?GT, the change of Gibbs free energy for the aggregation from monomer to the dimmer, is 26.47 kJ/mol at 298.15 K and 0.1 MPa, implying the spontaneous process of forming the dimer. The correlation graphics of S0m, H0m and temperatures is depicted.展开更多
The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-（CH3OH）n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six...The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-（CH3OH）n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six stable luteolin-（CH3OH）2 complexes and four stable luteolin-（CH3OH）3 complexes have been obtained.The theories of atoms in molecules（AIM） and natural bond orbital（NBO） have been used to analyze the hydrogen bonds of these compounds,and their interaction energies corrected by basis set superposition error are between-8.046 and-76.124 kJ/mol.The calculation results indicate strong hydrogen bonding interactions in the luteolin-（CH3OH）n complexes.Then the nuclear magnetic resonance（NMR） and electronic absorption spectrum of luteolin have been calculated,and the results are in agreement with the experimental data.展开更多
本文研究选用密度泛函理论中M06-2X及6-311G(d,p)基组,对由N-烷基乙二胺阳离子[HAlkyl]+(hexyl,octyl、2-ethylhexyl及EtHex)与双(三氟甲基磺酰)亚胺阴离子[TFSA]-形成的[HHex][TFSA]、[HOct][TFSA]及[HEtHex][TFSA]型质子化离子液体(Pr...本文研究选用密度泛函理论中M06-2X及6-311G(d,p)基组,对由N-烷基乙二胺阳离子[HAlkyl]+(hexyl,octyl、2-ethylhexyl及EtHex)与双(三氟甲基磺酰)亚胺阴离子[TFSA]-形成的[HHex][TFSA]、[HOct][TFSA]及[HEtHex][TFSA]型质子化离子液体(Protic ionic liquids,PILs)的分子间氢键相互作用进行理论研究,通过几何优化和分子振动频率分析得到其5种较稳定构型[HAlkyl][TFSA]S1~S5,结果表明:该类PILs的基组重叠误差(basis set superposition error,BSSE)校正后的分子间相互作用能ΔE int BSSE在-88.8^-108.9 kcal/mol范围内;由于阴阳离子间形成了较强的N—H…N或N—H…O型氢键,[HAlkyl]+阳离子中参与氢键的N—H键长延长,红外谱图显示N—H伸缩振动发生了红移,且红移值显著。通过自然键轨道理论分析可知,其稳定化能主要来源于阴离子[TFSA]-中N、O原子的孤对电子与阳离子[HAlkyl]+中N—H反键轨道之间的相互作用,即LP(N/O)→σ*(N—H)。采用分子中原子理论计算二阶微扰能E(2)值、电子密度ρc值及拉普拉斯值2ρc的结果表明,[HAlkyl]+中碳链的长短、支链的引入对[HAlkyl][TFSA]分子间氢键作用的强弱有较大的影响,并且在伯胺质子化构型(S1~S3)中形成的氢键相互作用比仲胺质子化构型(S4、S5)较强。展开更多
基金This work was supported by the Natural Science Foundation of Shandong Province (No. Y2002B06)
文摘Density functional theory (DFT) calculations on a double hydrogen-bonded dimer of o-hydroxybenzoic acid were carried out at the B3LYP/6-31G* level. The optimized geometry of the dimer closely resembles that of the crystal. The calculated results show that the total energy of the dimer is much lower than the sum energies of the two monomers, and the average strength of the double hydrogen bonds is about 38.37 kJ/mol. In order to probe the origin of the interactions in the dimer, natural bond orbital analyses were performed. The thermodynamic properties of the title compound at different temperatures have also been calculated on the basis of vibrational analyses and ?GT, the change of Gibbs free energy for the aggregation from monomer to the dimmer, is 26.47 kJ/mol at 298.15 K and 0.1 MPa, implying the spontaneous process of forming the dimer. The correlation graphics of S0m, H0m and temperatures is depicted.
文摘The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-（CH3OH）n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six stable luteolin-（CH3OH）2 complexes and four stable luteolin-（CH3OH）3 complexes have been obtained.The theories of atoms in molecules（AIM） and natural bond orbital（NBO） have been used to analyze the hydrogen bonds of these compounds,and their interaction energies corrected by basis set superposition error are between-8.046 and-76.124 kJ/mol.The calculation results indicate strong hydrogen bonding interactions in the luteolin-（CH3OH）n complexes.Then the nuclear magnetic resonance（NMR） and electronic absorption spectrum of luteolin have been calculated,and the results are in agreement with the experimental data.
文摘本文研究选用密度泛函理论中M06-2X及6-311G(d,p)基组,对由N-烷基乙二胺阳离子[HAlkyl]+(hexyl,octyl、2-ethylhexyl及EtHex)与双(三氟甲基磺酰)亚胺阴离子[TFSA]-形成的[HHex][TFSA]、[HOct][TFSA]及[HEtHex][TFSA]型质子化离子液体(Protic ionic liquids,PILs)的分子间氢键相互作用进行理论研究,通过几何优化和分子振动频率分析得到其5种较稳定构型[HAlkyl][TFSA]S1~S5,结果表明:该类PILs的基组重叠误差(basis set superposition error,BSSE)校正后的分子间相互作用能ΔE int BSSE在-88.8^-108.9 kcal/mol范围内;由于阴阳离子间形成了较强的N—H…N或N—H…O型氢键,[HAlkyl]+阳离子中参与氢键的N—H键长延长,红外谱图显示N—H伸缩振动发生了红移,且红移值显著。通过自然键轨道理论分析可知,其稳定化能主要来源于阴离子[TFSA]-中N、O原子的孤对电子与阳离子[HAlkyl]+中N—H反键轨道之间的相互作用,即LP(N/O)→σ*(N—H)。采用分子中原子理论计算二阶微扰能E(2)值、电子密度ρc值及拉普拉斯值2ρc的结果表明,[HAlkyl]+中碳链的长短、支链的引入对[HAlkyl][TFSA]分子间氢键作用的强弱有较大的影响,并且在伯胺质子化构型(S1~S3)中形成的氢键相互作用比仲胺质子化构型(S4、S5)较强。
