DFT/MRCI-R2018 study of the photophysics of the zinc(ii) tripyrrindione radical: non-Kasha emission?
DFT/MRCI-R2018 study of the photophysics of the zinc(ii) tripyrrindione radical: non-Kasha emission?
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DOI：
10.1039/c9cp04244j
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发表时间：
2019-09
期刊：
影响因子：
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通讯作者：
Adrian Heil;C. Marian
中科院分区：
文献类型：
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作者：
Adrian Heil;C. Marian
稳定的基于自由基的荧光发射体很少见，在室温下更是如此。最近，Gautam等人在实验上描述了锌(II)-三吡二酮配合物[Zn(Td1·)(H2O)]。作者声明：[Inorg.化学，2018年，57,15240]作为中性自由基发射体小家族的新成员，可能在电子和光子学中应用。在四氢呋喃溶液中，在最大吸收波长599 nm(2.07 eV)处激发，在室温下观察到最大荧光强度为644 nm(1.93 eV)。荧光能量高于从≈930 nm开始的几个低强度吸收带。在这里，我们用最近发展起来的半经验全重数密度泛函DFT/MRCI-R2018方法对该锌配合物的吸收和荧光进行了理论研究。DFT/MRCI方法结合了封闭壳或受限开壳Kohn-Sham轨道基中的密度泛函理论(DFT)和多参考组态相互作用(MRCI)。事实证明，R2018哈密顿量非常适合研究自由基锌络合物的性质。计算表明，吸收光谱主要受D3、D6和D11三个态的跃迁控制。实验观察到的发射带比自由基的最低吸收带的波长要短得多。这排除了作为发射来源的D1→D0过渡。我们的计算表明，这是一个非Kasha发射，D3是发射态。还讨论了解释实验观察到的发射的其他方法，如离子对的形成或脱金属后的配体发射。
Stable radical-based fluorescent emitters are rare, even more so at room temperature. The zinc(ii) tripyrrindione [Zn(TD1˙)(H2O)] complex has recently been described experimentally by Gautam et al. [Inorg. Chem., 2018, 57, 15240] as a new member of the small family of neutral radical emitters with possible applications in electronics and photonics. Upon excitation at the absorption maximum of 599 nm (2.07 eV), strong fluorescence was observed with a maximum at 644 nm (1.93 eV) at room temperature in tetrahydrofuran solution. The fluorescence energy is higher than several low-intensity absorption bands starting at ≈930 nm. Here we present a theoretical investigation into the absorption and fluorescence of this zinc complex by means of the recently developed semi-empirical all-multiplicity DFT/MRCI-R2018 method. The DFT/MRCI method combines density functional theory (DFT) in a closed shell or restricted open-shell Kohn-Sham orbital basis and multireference configuration interaction (MRCI). The R2018 Hamiltonian proves to be well-suited for investigating the properties of the radical-based zinc complex. The calculations reveal that the absorption spectrum is dominated by bright transitions to the D3, D6 and D11 states. The experimentally observed emission band lies at considerably shorter wavelengths than the lowest absorption band of the radical. This precludes the D1 → D0 transition as the origin of the emission. Our calculations indicate a non-Kasha emission, with D3 as the emissive state. Other ways of explaining the experimentally observed emission, such as ion-pair formation or ligand emission after demetalation, are discussed as well.