The elucidation of reaction mechanisms taking place in the excited state is a current challenge for experimental and theoretical chemists. Ru(II) complexes have a long history for photophysics, and there is currently an increasing interest in their photochemistry. Ru(II) complexes provide a vast field of exploration, whether for synthetic purposes, to trigger molecular motions or to release biologically active components. The excited states involved, especially those of MLCT and MC character, are key to the rationalization of their photophysical and photochemical properties. This review focuses on the recent progress in the latter field through several case studies: i) the archetypes [Ru(bpy)₃]²⁺ and [Ru(tpy)₂]²⁺ first serve for the validation of the theoretical methods we are using; ii) then the study of photorelease of a monodentate ligand provides us with novel mechanistic hypotheses; iii) one step further, studying the photorelease mechanism of a bidentate ligand provides us with novel ³MC states of peculiar flattened geometry; iv) finally, returning to [Ru(bpy)₃]²⁺ itself, we will show that the existence of these states can be generalized and probably represent a major player in the description of photoreactivity mechanisms, for ruthenium and possibly several other transition metals.

阐明在激发态下发生的反应机理是对实验和理论化学家的当前挑战。Ru（II）配合物在光物理领域具有悠久的历史，目前对它们的光化学越来越感兴趣。钌（II）配合物提供了广阔的探索领域，无论是出于合成目的，引发分子运动还是释放生物活性成分。所涉及的激发态，特别是MLCT和MC特性的激发态，是使其光物理和光化学性质合理化的关键。这篇综述着重通过几个案例研究了后者的最新进展：i）[Ru（bpy）₃ ] ²⁺和[Ru（tpy）₂ ] ²⁺的原型首先用于验证我们正在使用的理论方法；ii）然后对单齿配体的光释放进行研究为我们提供了新的机制假设；iii）进一步，研究双齿配体的光释放机理为我们提供了特殊的扁平几何形状的^3种MC状态；iv）最后，回到[Ru（bpy）₃ ] ²⁺本身，我们将证明这些状态的存在可以被概括，并且可能代表了光化学反应机理的主要参与者，对于钌以及可能还有其他几种过渡金属。