Machine-Learning Photodynamics Simulations Uncover the Role of Substituent Effects on the Photochemical Formation of Cubanes
Machine-Learning Photodynamics Simulations Uncover the Role of Substituent Effects on the Photochemical Formation of Cubanes
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DOI：
10.1021/jacs.1c07725
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发表时间：
2021-12-08
影响因子：
15
通讯作者：
Lopez, Steven A.
中科院分区：
文献类型：
--
作者：
Li, Jingbai;Stein, Rachel;Lopez, Steven A.
光化学[2 + 2]-环加成将太阳能储存在化学键中，并有效地获得应变的有机分子结构。官能化的[3]-梯二烯经过[2 + 2]-光环加成得到立方烷，一类应变有机分子。取代基（例如甲基、三氟甲基和环丙基）影响这些立方烷前体的整体反应性；收益率范围为 1% 至 48%。然而，这些取代基对反应性和化学选择性的影响的起源尚不清楚。我们现在集成单参考和多参考计算以及机器学习加速的非绝热分子动力学 (ML-NAMD)，以了解取代基如何影响 [2 + 2]-光环加成的超快动力学和机制。取代基之间的空间冲突使 4 π 电环开环途径和最小能量圆锥交叉点不稳定 0.72-1.15 eV，使反应能不稳定 0.68-2.34 eV。非共价分散相互作用稳定[2 + 2]-光环加成途径；圆锥交点能量降低0.31-0.85 eV，反应能量降低0.03-0.82 eV。 2 ps ML-NAMD 轨迹表明，随着空间体积的增加，闭壳排斥会阻碍 6 pi 旋转电环开环途径。 38％的甲基取代的[3]-梯二烯轨迹通过6π-旋转电环开环进行，而三氟甲基和环丙基取代的[3]-梯二烯更喜欢[2+2]-光环加成途径。预测的立方烷产率（H：0.4％<CH3：1％<CF3：14％<cPr：15％）与实验趋势相符；这些取代基使反应物预变形，使其类似于形成古巴的圆锥形交叉几何形状。
Photochemical [2 + 2]-cycloadditions store solar energy in chemical bonds and efficiently access strained organic molecular architectures. Functionalized [3]-ladderdienes undergo [2 + 2]-photocycloadditions to afford cubanes, a class of strained organic molecules. The substituents (e.g., methyl, trifluoromethyl, and cyclopropyl) affect the overall reactivities of these cubane precursors; the yields range from 1 to 48%. However, the origin of these substituent effects on the reactivities and chemoselectivities is not understood. We now integrate single and multireference calculations and machine-learning-accelerated nonadiabatic molecular dynamics (ML-NAMD) to understand how substituents affect the ultrafast dynamics and mechanism of [2 + 2]-photocycloadditions. Steric clashes between substituent groups destabilize the 4 pi-electrocyclic ring-opening pathway and minimum energy conical intersections by 0.72-1.15 eV and reaction energies by 0.68-2.34 eV. Noncovalent dispersive interactions stabilize the [2 + 2]-photocycloaddition pathway; the conical intersection energies are lower by 0.31-0.85 eV, and the reaction energies are lower by 0.03-0.82 eV. The 2 ps ML-NAMD trajectories reveal that closed-shell repulsions block a 6 pi-conrotatory electrocyclic ring-opening pathway with increasing steric bulk. Thirty-eight percent of the methylsubstituted [3]-ladderdiene trajectories proceed through the 6 pi-conrotatory electrocyclic ring-opening, whereas the trifluoromethyland cyclopropyl-substituted [3]-ladderdienes prefer the [2 + 2]-photocycloaddition pathways. The predicted cubane yields (H: 0.4% < CH3 : 1% < CF3 : 14% < cPr: 15%) match the experimental trend; these substituents predistort the reactants to resemble the conical intersection geometries leading to cubanes.