The molecular structures and electron affinities of 5- and 6-halouracils（XU, X=F, Cl, Br） were determined by means of five different density functional methods. The basis set used in this work is of double-（plus po...The molecular structures and electron affinities of 5- and 6-halouracils（XU, X=F, Cl, Br） were determined by means of five different density functional methods. The basis set used in this work is of double-（plus polariza- tion（DZP） quality with additional diffuse s- and p-type functions, denoted DZP＋＋. The geometries were fully optimized with each density functional theory（DFT） method, and discussed. Three different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity（AEA）, the vertical electron affinity（VEA）, and the vertical detachment energy（VDE）. An excellent agreement between our B3LYP results and those obtained by other calculations regarding the structural modifications and electron affinities of neutral and anion 5XU was found. The differences in charge distribution between uracil and halogenated uracils were indicated, thus the ability to form the hydrogen bonds of halogenated uracils was discussed. It shows the applicability of the DFT/DZP＋＋ method to predict the similar molecular models at a highly economical computational cost.展开更多
Theoretical study about the magnetic properties of conjugated organic molecules containing borepin with π current density was carried out. 1-（2,4,6-Trimethylphenyl）borepin moiety is the center and other different g...Theoretical study about the magnetic properties of conjugated organic molecules containing borepin with π current density was carried out. 1-（2,4,6-Trimethylphenyl）borepin moiety is the center and other different groups are situated on the both fl sides, which are named molecules 1--12 as theoretical model in order to establish the rela- tionship between aromaticity and geometry variation of borepin. The optimized molecular structures of molecules 1--12 are almost keeping planar and the C2--C3 bond length of borepin turns longer from molecule 1 to molecule 12 Different borepin-annulated ring could change the conjugated effect of π-electron between borepin and these bore- pin-annulated rings. Moreover, the molecule presents antiaromaticity, in other words, the molecule became unstable when the C2--C3 bond length of borepin extended more than ca. O. 1417 nm. But the fl position fragment and substi- tuent groups of borepin are not affected in this case, they are still steady. However, the central borepin ring current is counteracted by symmetrical overlap of it with affiliated borepin-annulated ring current. Hence, the central borepin ring breaking would be liable to occur. These molecules have higher vertical ionization potentials（VIPs） and lower vertical electron affinities（VEAs）, which suggests that these molecules could easily exist in anionic form.展开更多
基金Supported by the National Natural Science Foundation of China(No.20573042)
文摘The molecular structures and electron affinities of 5- and 6-halouracils（XU, X=F, Cl, Br） were determined by means of five different density functional methods. The basis set used in this work is of double-（plus polariza- tion（DZP） quality with additional diffuse s- and p-type functions, denoted DZP＋＋. The geometries were fully optimized with each density functional theory（DFT） method, and discussed. Three different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity（AEA）, the vertical electron affinity（VEA）, and the vertical detachment energy（VDE）. An excellent agreement between our B3LYP results and those obtained by other calculations regarding the structural modifications and electron affinities of neutral and anion 5XU was found. The differences in charge distribution between uracil and halogenated uracils were indicated, thus the ability to form the hydrogen bonds of halogenated uracils was discussed. It shows the applicability of the DFT/DZP＋＋ method to predict the similar molecular models at a highly economical computational cost.
基金Supported by the National Natural Science Foundation of China（Nos.21003057, 21173096） and the Specialized Research Fund for the Doctoral Program of Higher Education of China（No.20110061110018）.
文摘Theoretical study about the magnetic properties of conjugated organic molecules containing borepin with π current density was carried out. 1-（2,4,6-Trimethylphenyl）borepin moiety is the center and other different groups are situated on the both fl sides, which are named molecules 1--12 as theoretical model in order to establish the rela- tionship between aromaticity and geometry variation of borepin. The optimized molecular structures of molecules 1--12 are almost keeping planar and the C2--C3 bond length of borepin turns longer from molecule 1 to molecule 12 Different borepin-annulated ring could change the conjugated effect of π-electron between borepin and these bore- pin-annulated rings. Moreover, the molecule presents antiaromaticity, in other words, the molecule became unstable when the C2--C3 bond length of borepin extended more than ca. O. 1417 nm. But the fl position fragment and substi- tuent groups of borepin are not affected in this case, they are still steady. However, the central borepin ring current is counteracted by symmetrical overlap of it with affiliated borepin-annulated ring current. Hence, the central borepin ring breaking would be liable to occur. These molecules have higher vertical ionization potentials（VIPs） and lower vertical electron affinities（VEAs）, which suggests that these molecules could easily exist in anionic form.
