Multiphoton Control of 6π Photocyclization via State-Dependent Reactant–Product Correlations,The Journal of Physical Chemistry Letters

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Multiphoton Control of 6π Photocyclization via State-Dependent Reactant–Product Correlations
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2021-09-24 , DOI: 10.1021/acs.jpclett.1c02353
Ryan P Brady ₁ , Chaoqun Zhang ₁ , Justin R DeFrancisco ₁ , Brandon J Barrett ₁ , Lan Cheng ₁ , Arthur E Bragg ₁

Affiliation

Multiphoton excitation promises opportunities for opening new photochemical reaction pathways and controlling photoproduct distributions. We demonstrate photonic control of the 6π photocyclization of ortho-terphenyl to make 4a,4b-dihydrotriphenylene (DHT). Using pump–repump–probe spectroscopy we show that 1 + 1′ excitation to a high-lying reactant electronic state generates a metastable species characterized by a red absorption feature that accompanies a repump-induced depletion in the one-photon trans-dihydro product (trans-DHT); signatures of the new photoproduct are clearer for a structural analogue of the reactant that is sterically inhibited against one-photon cyclization. Quantum-chemical computations support assignment of this species to cis-DHT, which is accessible photochemically along a disrotatory coordinate from high-lying electronic states reached by 1 + 1′ excitation. We use time-resolved spectroscopy to track photochemical dynamics producing cis-DHT. In total, we demonstrate that selective multiphoton excitation opens a new photoreaction channel in these photocyclizing reactants by taking advantage of state-dependent correlations between reactant and product electronic states.

中文翻译：

通过状态相关反应物-产物相关性对 6π 光环化的多光子控制

多光子激发有望开辟新的光化学反应途径和控制光产物分布。我们展示了对邻三联苯的 6π 光环化的光子控制，以制备 4 a ,4 b -二氢联苯 (DHT)。使用泵 - 再泵 - 探针光谱，我们表明 1 + 1' 激发到高位反应物电子态会产生一种亚稳态物质，其特征是红色吸收特征伴随着单光子反式二氢产物中的再泵诱导耗尽（反式-DHT); 对于在空间上抑制单光子环化的反应物的结构类似物，新光产物的特征更加清晰。量子化学计算支持将该物种分配给顺式-DHT，它可以从 1 + 1' 激发达到的高位电子态沿反旋转坐标光化学地访问。我们使用时间分辨光谱来跟踪产生顺式DHT 的光化学动力学。总之，我们证明了选择性多光子激发通过利用反应物和产物电子状态之间的状态相关相关性，在这些光环化反应物中打开了一个新的光反应通道。

更新日期：2021-10-07

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