Density Functional Study on the Photopolymerization of Styrene Using Dinuclear Ru-Pd and Ir-Pd Complexes with Naphthyl-Substituted Ligands
Density Functional Study on the Photopolymerization of Styrene Using Dinuclear Ru-Pd and Ir-Pd Complexes with Naphthyl-Substituted Ligands
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双核 Ru-Pd 和 Ir-Pd 配合物与萘基取代配体光聚合苯乙烯的密度泛函研究
DOI：
10.1021/acs.jpca.3c01299
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Abe Minori
中科院分区：
文献类型：
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作者：
Salmahaminati;Inagaki Akiko;Hada Masahiko;Abe Minori
采用密度泛函方法研究了双核Ru-Pd和Ir-Pd催化配合物催化苯乙烯聚合的反应机理。在以前的实验中，这些催化剂的反应性增加，并产生更多的聚合物产物相比，在可见光照射下的二聚体。最好的催化反应性，得到使用的Ir-Pd配合物含有萘基取代基的苯基配体配位到Ir（Ir-Pd 1）。与此相反，Ir-Pd 1的异构体Ir-Pd 2，在吡啶配体上含有萘基取代基，没有表现出良好的反应性，这可能与催化配合物的激发态的稳定性有关。在本研究中，我们计算了这些催化配合物的辐射寿命，Ir-Pd 1具有最长的寿命，这一结果与实验结果相一致。Ir-Pd 1的最长寿命归因于萘基和苯基配体之间的π*−π* 相互作用使最高占据分子轨道（HOMO）能量不稳定。此外，HOMO能量的这种不稳定性在HOMO和最低未占分子轨道之间提供了小的能隙，增强了金属到配体的电荷转移到Ir和Pd之间的桥接配体。此外，我们专注于苯乙烯的第二次插入反应，这被确定为在以前的研究中的聚合循环的速率决定步骤。估算了中间产物的单重态-三重态交叉点，发现体系间交叉的势垒高度远低于热路径的势垒高度，这解释了实验中光催化活性的有效性。
A density functional study was performed to investigate the mechanism of the photocatalytic reactivity of styrene polymerization using dinuclear Ru–Pd and Ir–Pd catalytic complexes. In previous experiments with these catalysts, the reactivity increased, and more polymer products were yielded compared to dimers under visible light irradiation. The best catalytic reactivity was obtained using an Ir–Pd complex containing naphthyl substituents at the phenyl ligands coordinated to Ir (Ir–Pd1). In contrast,Ir–Pd2, an isomer ofIr–Pd1, containing naphthyl substituents at the pyridine ligands, did not show good reactivity, which may be related to the stability of the excited state of the catalytic complexes. In this study, we calculated the radiative lifetimes of these catalytic complexes andIr–Pd1had the longest lifetime; this result was consistent with the experimental results. The longest lifetime of theIr–Pd1was attributed to the destabilization of the highest occupied molecular orbital (HOMO) energy by π*−π* interactions between the naphthyl and phenyl ligands. Further, this destabilization of the HOMO energy afforded a small energy gap between the HOMO and lowest unoccupied molecular orbital, enhancing the metal-to-ligand charge transfer to the bridging ligand between Ir and Pd. Additionally, we focused on the reaction of the second insertion of styrene, which was identified as the rate-determining step of the polymerization cycle in a previous study. The singlet–triplet crossing points of the intermediates were estimated, and the barrier heights of the intersystem crossing were much lower than those in the thermal paths, which explained the efficiency of the photocatalytic reactivity in the experiment.