Direct Observation of an Alkylidenecarbene by Ultrafast Transient Absorption Spectroscopy
Direct Observation of an Alkylidenecarbene by Ultrafast Transient Absorption Spectroscopy
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DOI：
10.1021/acs.jpca.8b06118
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发表时间：
2018-08-30
影响因子：
2.9
通讯作者：
Thamattoor, Dasan M.
中科院分区：
文献类型：
--
作者：
Du, Lili;Lan, Xin;Thamattoor, Dasan M.
单重态α-甲基亚苄基卡宾已被检测到，并首次通过飞秒瞬态吸收（fs-TA）光谱表征。通过烃前体1-（1-苯基亚乙基）-1a，9 b-二氢-1H-环丙烯并[1]-菲在乙腈中的光解产生卡宾。光解最初形成的单重激发态的前体，然后挤出α-甲基亚苄基卡宾在4.0 ps。α-甲基亚苄基卡宾的衰变发生在13.3 ps以上，以前曾被证明通过1，2-苯基位移重排为苯基丙炔。在TD-B3 LYP/6-311+G** 水平上计算得到的光谱与实验结果一致。CASSCF（10，10）/6-311+G** 计算表明，以一种卡宾构象为模型，参考波函数受闭壳层描述支配.
Singlet alpha-methylbenzylidenecarbene has been detected and characterized for the first time by femtosecond transient absorption (fs-TA) spectroscopy. The carbene was generated by photolysis of the hydrocarbon precursor, 1-(1-phenylethylidene)-1a,9b-dihydro-1H-cyclopropa[l]-phenanthrene, in acetonitrile. The photolysis initially forms the singlet excited state of the precursor which then extrudes alpha-methylbenzylidenecarbene in 4.0 ps. The decay of alpha-methylbenzylidenecarbene, which was previously shown to rearrange into phenylpropyne by a 1,2-phenyl shift, occurred over 13.3 ps. Computed spectra at the TD-B3LYP/6-311+G** level of theory are consistent with the experimental observations. CASSCF(10,10)/6-311+G** calculations, using one of the carbene conformers as a model, indicated that the reference wave function is dominated by a closed-shell description.