Femtosecond photodecarbonylation of photo-ODIBO studied by stimulated Raman spectroscopy and density functional theory
Femtosecond photodecarbonylation of photo-ODIBO studied by stimulated Raman spectroscopy and density functional theory
复制标题
受激拉曼光谱和密度泛函理论研究photo-ODIBO的飞秒光脱羰作用
DOI：
10.1039/d1cp03512f
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发表时间：
2021
影响因子：
3.3
通讯作者：
Ullrich, Susanne
中科院分区：
文献类型：
--
作者：
Shenje, Learnmore;Qu, Yingqi;Popik, Vladimir;Ullrich, Susanne
Photo-oxa-二苯并环辛炔 (Photo-ODIBO) 在紫外线激发下经历光脱羰作用，形成明亮的 S2 态，形成高反应性环辛炔 ODIBO。在使用亚 50 fs 光化脉冲进行 321 nm 激发后，使用飞秒受激拉曼光谱和时间依赖性密度泛函理论拉曼计算来表征激发态演化和环丙烯酮键断裂以及 CO 释放。对 photo-ODIBO S2 CO 拉曼谱带的分析揭示了多指数强度、峰值分裂和频移动力学。这表明环丙烯酮结构中两个 C-C 键的逐步裂解在激发后 <300 fs 内完成。还观察到 S2 态分子内振动弛豫的证据，与光脱羰同时发生，其动力学与之前的电子瞬态吸收光谱相匹配。这证实了激发态（与基态相反）光脱羰机制产生振动激发光产物 ODIBO。
Photo-oxa-dibenzocyclooctyne (Photo-ODIBO) undergoes photodecarbonylation under UV excitation to its bright S2 state, forming a highly reactive cyclooctyne, ODIBO. Following 321 nm excitation with sub-50 fs actinic pulses, the excited state evolution and cyclopropenone bond cleavage with CO release were characterized using femtosecond stimulated Raman spectroscopy and time-dependent density functional theory Raman calculations. Analysis of the photo-ODIBO S2 CO Raman band revealed multi-exponential intensity, peak splitting and frequency-shift dynamics. This suggests a stepwise cleavage of the two C–C bonds in the cyclopropenone structure that is completed within <300 fs after excitation. Evidence of intramolecular vibrational relaxation on the S2 state, concurrent with photodecarbonylation, with dynamics matching previous electronic transient absorption spectroscopy, was also observed. This confirms an excited state, as opposed to ground state, photodecarbonylation mechanism resulting in a vibronically excited photoproduct, ODIBO.