Ground State Nuclear Magnetic Resonance Chemical Shifts Predict Charge-Separated Excited State Lifetimes
Ground State Nuclear Magnetic Resonance Chemical Shifts Predict Charge-Separated Excited State Lifetimes
复制标题
基态核磁共振化学位移预测电荷分离激发态寿命
DOI：
10.1021/acs.inorgchem.8b02087
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发表时间：
2018
影响因子：
4.6
通讯作者：
Kirk, Martin L.
中科院分区：
文献类型：
--
作者：
Yang, Jing;Kersi, Dominic K.;Richers, Casseday P.;Giles, Logan J.;Dangi, Ranjana;Stein, Benjamin W.;Feng, Changjian;Tichnell, Christopher R.;Shultz, David A.;Kirk, Martin L.
二苯并三茂烯铂(II)二亚胺配合物(LE，E‘)铂(Bpy)具有电荷分离的二卤三烯烯供体(Le，E’)→二亚胺受体(Bpy)配体-配体电荷转移(LL‘CT)激发态的特征，这使得它们具有有趣的光物理特性和在太阳能转换方面的潜在应用。尽管人们对这些络合物有浓厚的兴趣，但硫化物对三重态LL‘CT激发态寿命的依赖仍未得到解释。三个新的含混合硫配位的(LE，E‘)铂(Bpy)配合物的衰变速率主要由自旋-轨道介导的非辐射途径控制，其大小与混合硫配位配位环境提供的各向异性共价性成正比。这种各向异性的共价性在含硫基团的施主碳的~(13)C核磁共振化学位移中被戏剧性地揭示出来，并被S K-Edge XAS进一步探索。值得注意的是，核磁共振化学位移的差异还与连接三重态激发态和基态的自旋轨道矩阵元相关。因此，三重态LL‘CT激发态寿命与这两个函数成正比，表明特定的基态核磁共振化学位移可以用来评估自旋-轨道耦合对激发态寿命的贡献。
Dichalcogenolene platinum(II) diimine complexes, (LE,E′)Pt(bpy), are characterized by charge-separated dichalcogenolene donor (LE,E′) → diimine acceptor (bpy) ligand-to-ligand charge transfer (LL′CT) excited states that lead to their interesting photophysics and potential use in solar energy conversion applications. Despite the intense interest in these complexes, the chalcogen dependence on the lifetime of the triplet LL′CT excited state remains unexplained. Three new (LE,E′)Pt(bpy) complexes with mixed chalcogen donors exhibit decay rates that are dominated by a spin–orbit mediated nonradiative pathway, the magnitude of which is proportional to the anisotropic covalency provided by the mixed-chalcogen donor ligand environment. This anisotropic covalency is dramatically revealed in the13C NMR chemical shifts of the donor carbons that bear the chalcogens and is further probed by S K-edge XAS. Remarkably, the NMR chemical shift differences also correlate with the spin–orbit matrix element that connects the triplet excited state with the ground state. Consequently, triplet LL′CT excited state lifetimes are proportional to both functions, demonstrating that specific ground state NMR chemical shifts can be used to evaluate spin–orbit coupling contributions to excited state lifetimes.