Röhrs Milena, Escudero Daniel
Department of Chemistry, Quantum Chemistry and Physical Chemistry Division , KU Leuven , Celestijnenlaan 200F , B-3001 Heverlee , Belgium.
J Phys Chem Lett. 2019 Oct 3;10(19):5798-5804. doi: 10.1021/acs.jpclett.9b02477. Epub 2019 Sep 18.
In this Letter, we present first-principles evidence that several higher-lying excited states are responsible for the emission spectrum of [M(CO)4(bpy)] (M = Cr, Mo, W and bpy = 2,2'-bipyrimidine) complexes. These results highlight the violation of Kasha's rule, which states that after irradiation, molecules emit light with appreciable yield only from their lowest energy excited state. Furthermore, in [W(CO)4(bpy)] and [Mo(CO)4(bpy)], the breaking of Kasha's rule is two-fold because at least two different excited states besides T1 are involved in emission. To our knowledge, these are the first transition-metal complexes unambiguously demonstrated to display simultaneous equilibrated and nonequilibrated anti-Kasha emissions. This work also highlights the complexity of the emissive processes of tetracarbonyl-diimine transition-metal complexes, which are controlled via a subtle interplay of electronic and geometrical effects along the excited-state deactivation dynamics.
在本信函中，我们提供了第一性原理证据，表明几个较高能级的激发态对[M(CO)₄(bpy)]（M = Cr、Mo、W，bpy = 2,2'-联嘧啶）配合物的发射光谱有贡献。这些结果突出了对卡沙规则的违背，该规则指出，辐照后，分子仅从其最低能量激发态以可观的产率发射光。此外，在[W(CO)₄(bpy)]和[Mo(CO)₄(bpy)]中，卡沙规则的违背是双重的，因为除了T₁态之外，至少还有两个不同的激发态参与发射。据我们所知，这些是首批明确证明显示出同时存在平衡和非平衡反卡沙发射的过渡金属配合物。这项工作还突出了四羰基二亚胺过渡金属配合物发射过程的复杂性，其发射过程是通过沿激发态失活动力学的电子和几何效应的微妙相互作用来控制的。
