Singlet oxygen generation versus O–O homolysis in phenyl-substituted anthracene endoperoxides investigated by RASPT2, CASPT2, CC2, and TD-DFT methods
Singlet oxygen generation versus O–O homolysis in phenyl-substituted anthracene endoperoxides investigated by RASPT2, CASPT2, CC2, and TD-DFT methods
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通过 RASPT2、CASPT2、CC2 和 TD-DFT 方法研究苯基取代的蒽内过氧化物中单线态氧的生成与 OâO 均裂
DOI：
10.1007/s00214-012-1295-7
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发表时间：
2012
影响因子：
1.7
通讯作者：
L. González
中科院分区：
文献类型：
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作者：
S. Kupfer;G. Pérez-Hernández;L. González
本文用理论方法研究了氟苯基蒽内过氧化物1及其类似物2的单重态氧产生与O-O分裂的电子激发态。在较小的内过氧化物1的情况下，最近开发的二阶微扰理论限制的活性空间（RASPT 2）的方法已被采用和结果进行比较，从完整的活性空间（CASPT 2），二阶近似耦合簇（CC 2），和含时密度泛函理论（TD-DFT）的方法。除了垂直激发态外，还计算了导致均裂O-O解离的光化学路径。这个过程是由一个点，其中四个单重态和四个三重态几乎是简并的，并显示大量的自旋轨道耦合。用RASPT 2计算结果表明，S1态具有πoo*σoo* 特征，对应于O-O均裂解离，而Sn（n≥ 2）高激发态对应于局域激发和电荷转移激发，应与单线态氧的产生有关.用CASPT 2获得了类似的光化学图像，尽管需要两个不同的活性空间来描述光谱的不同部分。使用CC 2以及包含32%精确交换的泛函CAM-B3 LYP和B3 LYP（32）进行的计算显示出与RASPT 2能量的良好一致性，但在最低S1态中呈现出πoo*σoo* 和πoo*πan* 激发的强烈混合，与RASPT 2/CASPT 2的分配相矛盾。强烈不鼓励使用BP 86，因为它将大量电荷转移态错置在πoo*σoo* 态之下。用B3 LYP（32）计算的2的激发态与1的激发态非常相似，从而得出结论，两种内过氧化物应显示出相似的光化学，即与母体化合物蒽-9相比，O-O断裂似乎部分淬灭，单线态氧的产生增加，用RASPT 2对邻-氟-苯基-9-蒽-9，10-内过氧化物的不同电子激发态进行了基准测试。最低激发态对应于均裂O-O解离，较高激发态与单线态氧的产生有关。
AbstractThe electronic excited states corresponding to singlet oxygen generation versus O–O splitting ino-fluorine-phenyl-9-anthracene-9,10-endoperoxide1and its 9,10-bisarylanthracene analog2have been investigated using theoretical methods. In the case of the smaller endoperoxide1, the recently developed second-order perturbation theory restricted active space (RASPT2) method has been employed and the results are compared to those from the complete active space (CASPT2), second-order approximated coupled cluster (CC2), and time-dependent density functional theory (TD-DFT) approaches. In addition to the vertical excited states, the photochemical path leading to homolytic O–O dissociation has been computed. This process is governed by a point, where four singlet and four triplet states are almost degenerate and show substantial spin-orbit coupling. The results obtained with RASPT2 indicate that theS1state is of πoo*σoo*character, corresponding to the O–O homolytic dissociation, while higher excited statesSn(n≥ 2) correspond to local and charge transfer excitations and should be correlated to the generation of singlet molecular oxygen. A similar photochemical picture is obtained with CASPT2, although two different active spaces are required to describe different parts of the spectrum. The calculations carried out with CC2 as well as the functionals CAM-B3LYP and the B3LYP(32) containing 32 % of exact exchange show good agreement with the RASPT2 energies, but present a strong mixing of πoo*σoo*and πoo*πan*excitations in the lowestS1state, contradicting the assignment of RASPT2/CASPT2. The use of BP86 is strongly discouraged since it misplaces a large number of charge transfer states below the πoo*σoo*state. The excited states of2, calculated with B3LYP(32) are very similar to those of1, leading to the conclusion that both endoperoxides should show a similar photochemistry, that is, the O–O cleavage seems to be partially quenched and singlet oxygen generation is enhanced, in comparison with the parent compound, anthracene-9,10-endoperoxide.Graphical abstractThe different electronic excited states ofo-fluorine-phenyl-9-anthracene-9,10-endoperoxide have been benchmarked with RASPT2. The lowest excited state corresponds to the homolytic O–O dissociation and higher excited states are connected to singlet oxygen generation.
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