Sousa Carmen, Llunell Miquel, Domingo Alex, de Graaf Coen
Departament de Ciència de Materials i Química Física and Institut de Química Teòrica i Computacional, Universitat de Barcelona, C/Mart i Franquès 1, 08028 Barcelona, Catalunya, Spain.
Phys Chem Chem Phys. 2018 Jan 24;20(4):2351-2355. doi: 10.1039/c7cp08098k.
Spin-orbit couplings have been calculated in twenty snapshots of a molecular dynamics trajectory of [Fe(bpy)] to address the importance of geometrical distortions and second-order spin-orbit coupling on the intersystem crossing rate constants in the light-induced spin crossover process. It was found that the effective spin-orbit coupling between the MLCT and T state is much larger than the direct coupling in the symmetric structure, which opens the possibility of a direct MLCT-T deactivation without the intervention of triplet metal-centered states. Based on the calculated deactivation times, we conclude that both the direct pathway and the one involving intermediate triplet states are active in the ultrafast population of the metastable HS state, bringing in agreement two experimental observations that advocate for either deactivation mechanism. This resolves a long-standing dispute about the deactivation mechanism of Fe(ii)-polypyridyl complexes in particular, and about light-induced magnetism in transition metal complexes in general.
通过计算[Fe(bpy)]分子动力学轨迹的二十个快照中的自旋-轨道耦合，以探讨几何畸变和二阶自旋-轨道耦合对光致自旋交叉过程中系间窜越速率常数的重要性。研究发现，MLCT态和T态之间的有效自旋-轨道耦合远大于对称结构中的直接耦合，这为在没有三重态金属中心态干预的情况下直接发生MLCT-T失活提供了可能性。基于计算出的失活时间，我们得出结论，直接途径和涉及中间三重态的途径在亚稳HS态的超快布居过程中均起作用，这与支持任一失活机制的两个实验观察结果相一致。这解决了特别是关于Fe(ii)-多吡啶配合物失活机制以及一般过渡金属配合物中光致磁性的长期争议。
