Li Tian-Yi, Muthiah Ravinson Daniel Sylvinson, Haiges Ralf, Djurovich Peter I, Thompson Mark E
Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
J Am Chem Soc. 2020 Apr 1;142(13):6158-6172. doi: 10.1021/jacs.9b13755. Epub 2020 Mar 17.
A series of (carbene)Au(aryl) complexes are reported. The nature of the lowest excited state in these complexes changes character from metal-to-ligand charge transfer (MLCT) to interligand charge transfer (ICT) with increasing electron-donating strength of the aryl ligand. Complexes that have the MLCT lowest excited state undergo a Renner-Teller bending distortion upon excitation. Such a distortion leads to a large rate of nonradiative decay, on the order of 10 s. Renner-Teller-based nonradiative decay does not occur in chromophores with an ICT emissive state. Introducing a julolidine moiety and -methyl substituents to the aryl group makes the molecule rigid and hinders the rotation along the Au-C-coordinate bond. Consequently, the nonradiative decay rates of these ICT emitters are decreased and become lower than the radiative decay rate constants ( = 10 s). Thus, high-luminescent efficiencies (Φ = 0.61 and 0.77) along with short lifetimes (τ < 2 μs) are obtained for yellow and green emitters, respectively. Thermally assisted delayed fluorescence behavior is observed, owing to the small exchange energy (Δ < 1600 cm) in these emitters.
报道了一系列（卡宾）金（芳基）配合物。随着芳基配体给电子强度的增加，这些配合物中最低激发态的性质从金属到配体的电荷转移（MLCT）转变为配体间电荷转移（ICT）。具有MLCT最低激发态的配合物在激发时会发生伦纳 - 泰勒弯曲畸变。这种畸变导致约10⁹ s⁻¹的非辐射衰变率。基于伦纳 - 泰勒的非辐射衰变在具有ICT发射态的发色团中不会发生。在芳基上引入呫吨酮部分和甲基取代基使分子刚性增强，并阻碍沿金 - 碳配位键的旋转。因此，这些ICT发射体的非辐射衰变率降低，低于辐射衰变率常数（kr = 10⁶ s⁻¹）。这样，分别获得了黄色和绿色发射体的高发光效率（Φ = 0.61和0.77）以及短寿命（τ < 2 μs）。由于这些发射体中的交换能较小（ΔE < 1600 cm⁻¹），观察到了热激活延迟荧光行为。
