The C--H…H dihydrogen-bonded complexes of methane, ethylene, acetylene, and their derivatives with magnesium hydride were systematically investigated at MP2/aug-cc-PVTZ level. The results confirm that the strength of...The C--H…H dihydrogen-bonded complexes of methane, ethylene, acetylene, and their derivatives with magnesium hydride were systematically investigated at MP2/aug-cc-PVTZ level. The results confirm that the strength of dihydrogen bonding increases in the following order of proton donors： C（sp3）-H〈C（sp2）-H〈C（sp）-H and chlorine substituents enhance the C-H…H interaction. In the majority of the complexes with a cyclic structure, the Mg-H proton-accepting bond is more sensitive to the surroundings than C-H proton-donating bond. The nature of the electrostatic interaction in these C-H…H dihydrogen bonds was also unveiled by means of the atoms in mo- lecules（AIM） analysis. The natural bond orbital（NBO） analysis suggests that the charge transfer in the cyclic com- plexes is characteristic of dual-channel. The direction of the net charge transfer in the cyclic complexes is contrary to that previously found in dihydrogen bonded systems.展开更多
The present research employs density functional theory(DFT)computations to analyze the structure and energy of complexes formed by psoralen drug with alkali(Li^(+),Na^(+),K^(+))and alkaline earth(Be^(2+),Mg^(2+),Ca^(2...The present research employs density functional theory(DFT)computations to analyze the structure and energy of complexes formed by psoralen drug with alkali(Li^(+),Na^(+),K^(+))and alkaline earth(Be^(2+),Mg^(2+),Ca^(2+))metal cations.The computations are conducted on M06-2X/aug-cc-pVTZ level of theory in the gas phase and solution.The Atoms in Molecules(AIM)and natural bond orbital(NBO)analyses are applied to evaluating the characterization of bonds and the atomic charge distribution,respectively.The results show that the absolute values of binding energies decrease with going from the gas phase to the solution.Furthermore,the considered complexes in the water(as a polar solvent)are more stable than the CCl_(4)(as a non-polar solvent).The DFT based chemical reactivity indices,such as molecular orbital energies,chemical potential,hardness and softness are also investigated.The outcomes show that the considered complexes have high chemical stability and low reactivity from the gas phase to the solution.Finally,charge density distributions and chemical reactive sites of a typical complex explored in this study are obtained by molecular electrostatic potential surface.展开更多
A series of shikonin derivatives have been designed and their radical scavenging activity has been characterized by the B3LYP/6-31 ＋G（d） approach. The hydrogen bond properties of the studied structures were investi...A series of shikonin derivatives have been designed and their radical scavenging activity has been characterized by the B3LYP/6-31 ＋G（d） approach. The hydrogen bond properties of the studied structures were investigated using the atoms in molecules （AIM） theory. The calculated results reveal that the hydrogen bond is important for good scavenging activity. The introduction of electron-drawing （electron-donating） groups increases （decreases） the scavenging activities of radical and radical cations of shikonin derivatives. Shikonin derivatives appear to be good candidates for the single-electron-transfer mechanism, particularly for -N（CH3）2 derivative. Taking this system as an example, we present an efficient method for the investigation of radical scavenging activity from theoretical point of view. With the current work, we hope to highlight the radical scavenging activity of hydroxynaphtho- quinones derivatives and stimulate the interest for further studies and exploitation in pharmaceutical industry.展开更多
基金Supported by the National Natural Science Foundation of China（Nos.21003057, 21173096）, the National Basic Research Program of China（No.2013CB834801） and the Specialized Research Fund for the Doctoral Program of Higher Education of China（No.20110061110018）.
文摘The C--H…H dihydrogen-bonded complexes of methane, ethylene, acetylene, and their derivatives with magnesium hydride were systematically investigated at MP2/aug-cc-PVTZ level. The results confirm that the strength of dihydrogen bonding increases in the following order of proton donors： C（sp3）-H〈C（sp2）-H〈C（sp）-H and chlorine substituents enhance the C-H…H interaction. In the majority of the complexes with a cyclic structure, the Mg-H proton-accepting bond is more sensitive to the surroundings than C-H proton-donating bond. The nature of the electrostatic interaction in these C-H…H dihydrogen bonds was also unveiled by means of the atoms in mo- lecules（AIM） analysis. The natural bond orbital（NBO） analysis suggests that the charge transfer in the cyclic com- plexes is characteristic of dual-channel. The direction of the net charge transfer in the cyclic complexes is contrary to that previously found in dihydrogen bonded systems.
文摘The present research employs density functional theory(DFT)computations to analyze the structure and energy of complexes formed by psoralen drug with alkali(Li^(+),Na^(+),K^(+))and alkaline earth(Be^(2+),Mg^(2+),Ca^(2+))metal cations.The computations are conducted on M06-2X/aug-cc-pVTZ level of theory in the gas phase and solution.The Atoms in Molecules(AIM)and natural bond orbital(NBO)analyses are applied to evaluating the characterization of bonds and the atomic charge distribution,respectively.The results show that the absolute values of binding energies decrease with going from the gas phase to the solution.Furthermore,the considered complexes in the water(as a polar solvent)are more stable than the CCl_(4)(as a non-polar solvent).The DFT based chemical reactivity indices,such as molecular orbital energies,chemical potential,hardness and softness are also investigated.The outcomes show that the considered complexes have high chemical stability and low reactivity from the gas phase to the solution.Finally,charge density distributions and chemical reactive sites of a typical complex explored in this study are obtained by molecular electrostatic potential surface.
文摘A series of shikonin derivatives have been designed and their radical scavenging activity has been characterized by the B3LYP/6-31 ＋G（d） approach. The hydrogen bond properties of the studied structures were investigated using the atoms in molecules （AIM） theory. The calculated results reveal that the hydrogen bond is important for good scavenging activity. The introduction of electron-drawing （electron-donating） groups increases （decreases） the scavenging activities of radical and radical cations of shikonin derivatives. Shikonin derivatives appear to be good candidates for the single-electron-transfer mechanism, particularly for -N（CH3）2 derivative. Taking this system as an example, we present an efficient method for the investigation of radical scavenging activity from theoretical point of view. With the current work, we hope to highlight the radical scavenging activity of hydroxynaphtho- quinones derivatives and stimulate the interest for further studies and exploitation in pharmaceutical industry.
