The photoinduced bond cleavage and quenching of the α-phenoxylacetophenone excitation states can serve as a template to investigate fundamental photochemical processes. In this work, the absorption and emission spect...The photoinduced bond cleavage and quenching of the α-phenoxylacetophenone excitation states can serve as a template to investigate fundamental photochemical processes. In this work, the absorption and emission spectra as well as the photodecomposition mechanisms of α-phenoxylacetophenone were studied. The density functional theory（DFT） calculations revealed that： 1） the absorption spectra in methanol obtained by the M06-2X functional agree well with those by the B3LYP one; 2） the wavelength of the strongest peak acquired with the B3LYP method is slightly higher than the M06-2X one by 20.07 nm; 3） the βC–C bond in S1 can be broken directly.展开更多
The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calcula...The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calculation, CPCM full optimization is better to model solvent environments to gain reasonable reaction mechanisms. The π interactions play a significant role in the decarboxylation of pyrrole-2-carboxylic acid （R）. Firstly, the a hydrogen is protonated, but all of the carbonyl hydration pathways bear relatively higher energy barriers. The carbonyl group can rove over the pyrrole ring, but it does not lead to the speciation of pyrrole and protonated carbon dioxide for the latter is an energy-rich species. The decarboxylation mechanism proposed here is that, the protonated pyrrole-2-carboxylic acid （RH） decarboxylates via direct C-C bond cleavage with the aid of a water molecule to accommodate the proton on the carbonyl group.展开更多
Silicones can be cross-linked to materials with a wide variety of properties.In this work,the ringed oligomers of [SiO(OH)_2]nas well as the stacked structures of trimer and the linear strands of the dimer and trimer ...Silicones can be cross-linked to materials with a wide variety of properties.In this work,the ringed oligomers of [SiO(OH)_2]nas well as the stacked structures of trimer and the linear strands of the dimer and trimer were investigated systematically at B3 LYP/6-311 + + G(d,p) level combined with the conductor-like screening model(CPCM).This theoretical model reveals that,(1) SiO(OH)_2 will condense to stable ringed structures with SiO tetrahedrons;(2) in the ringed octamer [SiO(OH)_2]8,the macrocycle begins to pucker drastically;(3) from the linear strands of SiO rings it can be seen that the longer the chain is,the greater the energies decrease;(4) in [SiO(OH)_2]n(n ≥5) and in the strands of ringed oligomers,the highest occupied molecular orbitals(HOMOs) are primarily the n orbitals of the lone-pair electrons of oxygen atoms,so there are no delocalized π bonds.展开更多
基金supported by the National Natural Science Foundation of China(21571137,21502136 and 41402319)
文摘The photoinduced bond cleavage and quenching of the α-phenoxylacetophenone excitation states can serve as a template to investigate fundamental photochemical processes. In this work, the absorption and emission spectra as well as the photodecomposition mechanisms of α-phenoxylacetophenone were studied. The density functional theory（DFT） calculations revealed that： 1） the absorption spectra in methanol obtained by the M06-2X functional agree well with those by the B3LYP one; 2） the wavelength of the strongest peak acquired with the B3LYP method is slightly higher than the M06-2X one by 20.07 nm; 3） the βC–C bond in S1 can be broken directly.
基金supported by the National Natural Science Foundation of China(11174215)Natural Science Foundation of Shandong Province(ZR2012BL10 and ZR2010BL017)+1 种基金the University Science and Technology Project of Shandong Province(No.J13LD05)the Science and Technology Planning Project of Tai'an City(20102024)
文摘The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calculation, CPCM full optimization is better to model solvent environments to gain reasonable reaction mechanisms. The π interactions play a significant role in the decarboxylation of pyrrole-2-carboxylic acid （R）. Firstly, the a hydrogen is protonated, but all of the carbonyl hydration pathways bear relatively higher energy barriers. The carbonyl group can rove over the pyrrole ring, but it does not lead to the speciation of pyrrole and protonated carbon dioxide for the latter is an energy-rich species. The decarboxylation mechanism proposed here is that, the protonated pyrrole-2-carboxylic acid （RH） decarboxylates via direct C-C bond cleavage with the aid of a water molecule to accommodate the proton on the carbonyl group.
基金National Natural Science Foundations of China(Nos.21502136 and 21571137)Natural Science Foundation of Shandong Province,China(No.ZR2012BL10)the University Science and Technology Project of Shandong Province,China(No.J13LD05)
文摘Silicones can be cross-linked to materials with a wide variety of properties.In this work,the ringed oligomers of [SiO(OH)_2]nas well as the stacked structures of trimer and the linear strands of the dimer and trimer were investigated systematically at B3 LYP/6-311 + + G(d,p) level combined with the conductor-like screening model(CPCM).This theoretical model reveals that,(1) SiO(OH)_2 will condense to stable ringed structures with SiO tetrahedrons;(2) in the ringed octamer [SiO(OH)_2]8,the macrocycle begins to pucker drastically;(3) from the linear strands of SiO rings it can be seen that the longer the chain is,the greater the energies decrease;(4) in [SiO(OH)_2]n(n ≥5) and in the strands of ringed oligomers,the highest occupied molecular orbitals(HOMOs) are primarily the n orbitals of the lone-pair electrons of oxygen atoms,so there are no delocalized π bonds.
