β-苄基苯乙酮吸收与发射光谱的密度泛函研究
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摘要
β-苯基羰基化合物的光化学特征历来受到重视,是n,π*羰基三线态猝灭机理的典型代表。研究了气相和甲醇中β-苄基苯乙酮的基态结构和激发态结构,模拟了其吸收和发射光谱,并从分子轨道角度阐明了其发光机制。研究发现:(1)在甲醇中,β-苄基苯乙酮的基态结构与气相结构非常接近,只是在羰基官能团附近键长有差别;(2)在甲醇中,β-苄基苯乙酮的S1态无法维持平面构型,且αC—C键显著拉长;(3)在气相中,β-苄基苯乙酮的吸收光谱很弱,而在甲醇中很强;(4)气相中,β-苄基苯乙酮的荧光光谱的发光机制与甲醇中不同;(5)在气相中,β-苄基苯乙酮荧光光谱的最大发射峰蓝移到228.67nm处,发射强度(f=0.306 1)比吸收光谱大幅增加;(6)从分子轨道角度看,荧光光谱是吸收光谱的逆过程;(7)在气相中,β-苄基苯乙酮的磷光光谱在252.58和246.04nm处有两个较强的发射峰,而甲醇中只在258.88nm处有一个很强的发射峰。
The photochemistry of carbonyl compounds containingβ-phenyl rings has attracted increasing attention,for it is regarded as a representative template for the triplet n,π*quenching of carbonyl groups.In gas phase and in methanol,the ground states and excitation states ofβ-benzylacetophenone were investigated and its absorption and emission spectra were simulated.Besides,the luminescence mechanisms were also elucidated from molecular orbitals.The theoretical results revealed that:(1)Its ground-state structure in methanol is very close to the geometry in gas phase except for the bond distances around the carbonyl group;(2)In methanol,the S1 state ofβ-benzylacetophenone can not maintain a planar configuration,and theαC—C bond is extended significantly;(3)The absorption spectrum ofβ-benzylacetophenone is very weak in gas phase,but it is very strong in methanol;(4)The fluorescence spectrum ofβ-benzylacetophenone in gas phase is also different from that in methanol;(5)In gas phase,the strongest emission peak of the fluorescence spectrum is blue-shifted to about 228.67 nm,and its oscillator strength(f=0.306 1)increases significantly;(6)The fluorescence spectrum is an inverse process of the absorption spectrum from the viewpoint of molecular orbitals;(7)In phosphorescence spectrum,there are two relatively strong emission peaks at252.58 and 246.04 nm in gas phase,but there is only one very strong emission peak at 258.88 nm in methanol.
The photochemistry of carbonyl compounds containingβ-phenyl rings has attracted increasing attention,for it is regarded as a representative template for the triplet n,π*quenching of carbonyl groups.In gas phase and in methanol,the ground states and excitation states ofβ-benzylacetophenone were investigated and its absorption and emission spectra were simulated.Besides,the luminescence mechanisms were also elucidated from molecular orbitals.The theoretical results revealed that:(1)Its ground-state structure in methanol is very close to the geometry in gas phase except for the bond distances around the carbonyl group;(2)In methanol,the S1 state ofβ-benzylacetophenone can not maintain a planar configuration,and theαC—C bond is extended significantly;(3)The absorption spectrum ofβ-benzylacetophenone is very weak in gas phase,but it is very strong in methanol;(4)The fluorescence spectrum ofβ-benzylacetophenone in gas phase is also different from that in methanol;(5)In gas phase,the strongest emission peak of the fluorescence spectrum is blue-shifted to about 228.67 nm,and its oscillator strength(f=0.306 1)increases significantly;(6)The fluorescence spectrum is an inverse process of the absorption spectrum from the viewpoint of molecular orbitals;(7)In phosphorescence spectrum,there are two relatively strong emission peaks at252.58 and 246.04 nm in gas phase,but there is only one very strong emission peak at 258.88 nm in methanol.
引文
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