硫代羰基化合物激发态结构及光化学反应的理论预示  

Theoretical Prediction of the Structures and Reactivity of Thiocarbonyl Compounds in Excited States

作　　者：林玲[1] 丁万见[1] 方维海[1] 刘若庄[1] 

机构地区：[1]北京师范大学化学系,北京100875

出　　处：《化学学报》2003年第1期1-7,共7页Acta Chimica Sinica

基　　金：国家自然科学基金 (Nos.2 0 0 730 0 5;2 0 2 330 2 0 );博士点基金 (No.2 0 0 0 0 0 2 70 2 );基础研究重大项目前期研究专项基金 (No .2 0 0 1CCD0 350 0 )资助项目

摘　　要：运用精确的量子化学计算方法 ,优化了几种硫代羰基化合物 (H2 CS ,CH3CHS和CH3CSCH3)的基态和激发态的结构 ,计算了它们的相对能量 .不同的方法得到的结构参数比较一致 ,并与可用的实验结果相符 .计算结果表明 ,三个分子的S1,T1和T2 态的能量非常接近 ,而S2 态的能量明显高于T2 态 .这个理论结果与先前关于CH2 CH2 ,CH2 CHO和CH2 CH—CHCH2 的研究的结论是一致的 .用不同的方法对基态和最低三态的解离途径进行了理论优化 ,得到的结果较好地一致 .并且利用优化的基态和最低三态解离的势能剖面 ,和光激发到各个电子态的可用能量 。Carbonyl compounds are a kind of the most important organic compounds. Because of the unique electronic structures of carbonyl compounds, their photochemistry has been extensively investigated both theoretically and experimentally in the past decades. In comparison, thiocarbonyl compounds have received less attention, particularly their excited-state properties and photochemical reactions. In the present work, high-level quantum chemical ab initio methods were used to investigate the structures and energies of H2CS, CH3CHS and CH3CSCH3 in the ground and excited states. It is found that the structural parameters by different computational methods and different basis sets are similar, which are in agreement with the experimental results. The present calculations predict that the S-1 T-1 and T-2 states are close to each other in energy. However, there is a large difference in energy between the S-2 and T-2 states. The similar conclutions were found for molecules of CH2 = CH2, CH2CHO and CH2 = CH-CH = CH2. Upon photoexcitation at 500 nm, the systems do not have enough internal energy to overcome the barrier on the T-1 pathway. Thus internal conversion to the ground state is the most probable pathway to deactivate. Photoexcitation at 210 nm results in the molecules in the S-2 states. From this state, the molecules that relax to the T-1 state are left with sufficient internal energy to undergo the C-H or C-C bond dissocition along the T-1 pathway.

关 键 词：激发态结构 光化学反应 从头算 硫代羰基化合物 硫代甲醛 硫代乙醛 硫代丙酮 反应机理 量子化学 

分 类 号：O621[理学—有机化学]