DFT method was employed to locate transition state for H-atom transfer from phenol by methyl radical and methylperoxyl radical. The reaction pathway energy profiles and the structure of transition state show that a co...DFT method was employed to locate transition state for H-atom transfer from phenol by methyl radical and methylperoxyl radical. The reaction pathway energy profiles and the structure of transition state show that a common feature is the out-of-plane structure of the transition state: in contrast to the en- ergetic minima of a hydrogen-bonded intermediate, the hydrogen bond in transition structures is con- siderably twisted out of the aromatic ring. From the values of enthalpy (△H) and activation energy (Ea) obtained, it is found that the rate of the reaction of peroxyl radical with phenolic antioxidant is higher than that of alkyl radical with antioxidant. Spin density distributions show that the electron transmis- sion is between methyl (methylperoxyl) radical and phenol.展开更多
The polaron might play an important role in the process of charge migration through duplex DNA stack. In the present work, we investigate properties of hole polarons in DNA molecules containing identical base pairs, s...The polaron might play an important role in the process of charge migration through duplex DNA stack. In the present work, we investigate properties of hole polarons in DNA molecules containing identical base pairs, such as poly(G)-poly(C) and poly(A)-poly(T), An extended tight-binding model (extended Su-Schrieffer-Heeger model), which involves the effect of an electric field in the direction of DNA stack, will be introduced. The transfer integral and electron-phonon coupling parameters in this model are obtained according to ab initio calculation for different base pair dimers. Calculations reveal that the polaron in poly(A)-poly(T) has a wider shape and a higher mobility under a specific electric field than that in poly(G)-poly(C) DNA stack.展开更多
The theoretical study on magneto- structural correlation in linear trinuclear Cu (II) com- plex bridged by hydroxo group and bidentate formato group has been performed using the broken symme- try approach with the fra...The theoretical study on magneto- structural correlation in linear trinuclear Cu (II) com- plex bridged by hydroxo group and bidentate formato group has been performed using the broken symme- try approach with the framework of density functional theory (DFT-BS). The magnetic coupling constant for the model complex is 70.97 cm?1, comparable with the experimentally measured J value (77 cm?1). The calculated results show that the magnetic coupling interaction firstly slightly increases with the changes of the coordination environment around the terminal Cu atoms from a distorted square pyramid to a trigonal bi-pyramid, and decreases subsequently. In the course of changes, the sign of J value shifts from positive to negative. The magnetic coupling interac- tion is sensitive to coordination environment of the terminal Cu. The calculated results also reveal that the ferromagnetic coupling arises from the counter- complementarity of the hydroxo and formato bridges. Molecular orbital analysis validates the conclusion.展开更多
基金Supported by the Shandong Province Outstanding Middle-aged Scientists Research Foundation of China (Grant No. 2005BS04009) the Jinan City Youth Star Tech-nology Research Foundation (Grant No. 08109)
文摘DFT method was employed to locate transition state for H-atom transfer from phenol by methyl radical and methylperoxyl radical. The reaction pathway energy profiles and the structure of transition state show that a common feature is the out-of-plane structure of the transition state: in contrast to the en- ergetic minima of a hydrogen-bonded intermediate, the hydrogen bond in transition structures is con- siderably twisted out of the aromatic ring. From the values of enthalpy (△H) and activation energy (Ea) obtained, it is found that the rate of the reaction of peroxyl radical with phenolic antioxidant is higher than that of alkyl radical with antioxidant. Spin density distributions show that the electron transmis- sion is between methyl (methylperoxyl) radical and phenol.
基金Supported by the Major State Basic Research Development Programs of China (Grant No. 2004CB719902)the National Natural Science Foundation of China (Grant Nos. 20633060 and 20503014)
文摘The polaron might play an important role in the process of charge migration through duplex DNA stack. In the present work, we investigate properties of hole polarons in DNA molecules containing identical base pairs, such as poly(G)-poly(C) and poly(A)-poly(T), An extended tight-binding model (extended Su-Schrieffer-Heeger model), which involves the effect of an electric field in the direction of DNA stack, will be introduced. The transfer integral and electron-phonon coupling parameters in this model are obtained according to ab initio calculation for different base pair dimers. Calculations reveal that the polaron in poly(A)-poly(T) has a wider shape and a higher mobility under a specific electric field than that in poly(G)-poly(C) DNA stack.
基金This work was supported by the Major State Basic Research Development Programs(Grant No.2004CB719902)the National Natural Science Foundation of China(Grant No.20373033).
文摘The theoretical study on magneto- structural correlation in linear trinuclear Cu (II) com- plex bridged by hydroxo group and bidentate formato group has been performed using the broken symme- try approach with the framework of density functional theory (DFT-BS). The magnetic coupling constant for the model complex is 70.97 cm?1, comparable with the experimentally measured J value (77 cm?1). The calculated results show that the magnetic coupling interaction firstly slightly increases with the changes of the coordination environment around the terminal Cu atoms from a distorted square pyramid to a trigonal bi-pyramid, and decreases subsequently. In the course of changes, the sign of J value shifts from positive to negative. The magnetic coupling interac- tion is sensitive to coordination environment of the terminal Cu. The calculated results also reveal that the ferromagnetic coupling arises from the counter- complementarity of the hydroxo and formato bridges. Molecular orbital analysis validates the conclusion.
