Diradical Character and Second Hyperpolarizability of Alkaline Earth Metal Inverse Sandwich Complexes Involving Cyclopentadienyl and Cyclooctatetraene Ligands
Diradical Character and Second Hyperpolarizability of Alkaline Earth Metal Inverse Sandwich Complexes Involving Cyclopentadienyl and Cyclooctatetraene Ligands
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DOI：
10.1002/ejic.201800267
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发表时间：
2018-06
影响因子：
2.3
通讯作者：
S. Takamuku;M. Nakano
中科院分区：
文献类型：
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作者：
S. Takamuku;M. Nakano
利用强相关量子化学计算，我们揭示了碱土金属反夹心配合物（4-Mg，4-Ca，8-Mg，8-Ca）的二自由基性质与二阶超极化率γ[三阶非线性光学（NLO）性质]之间的关系。用价组态相互作用（VCI）模型对双自由基性质进行了详细的分析，发现高周期金属导致较大的金属-金属距离（0.8-0.9），而较大的有机配体环尺寸导致较小的双自由基性质，这是由于金属间的转移积分较大（距离较小）。这些特点是解释了轨道图和VCI分析。发现8-Ca的γ值最大，是γ值最小的8-Mg的4.94倍。从这些结果中，我们得到了基于碱土金属反夹心配合物的有效三阶非线性光学系统的设计准则：具有较高周期数的碱土金属和较大的有机反芳环（4 n π）的组合倾向于提高γ值，这是由于较大的金属-金属距离而保持中间值。
Using strong‐correlated quantum chemical calculations, we have revealed the relationship between diradical characteryand second hyperpolarizabilityγ[third‐order nonlinear optical (NLO) property] in alkaline earth metal inverse sandwich complexes, which have Mg or Ca atoms as an alkaline earth metal and a four‐ or eight‐membered ring as an organic ligand (4‐Mg,4‐Ca,8‐Mg, and8‐Ca). Through detailed analysis of diradical character with the valence configuration interaction (VCI) model, we have found that the higher period metal leads to a larger metal–metal distance with largeryvalue 0.8–0.9, while a larger ring size of organic ligand leads to smaller diradical character values due to the larger transfer integral (smaller distance) between metals. These features are explained by orbital diagrams and VCI analysis. Indeed, it is found that8‐Cahas the largestγvalue, which is 4.94 times as large as that of the system with the smallestγvalue (8‐Mg). From these results, we obtain a design guideline for efficient third‐order NLO systems based on alkaline earth metal inverse sandwich complexes: a combination of alkaline earth metal with a higher period number and larger organic antiaromatic (4nπ) ring tends to enhance theγvalue due to the larger metal–metal distance with keeping an intermediateyvalue.