Spin–vibronic coherence drives singlet–triplet conversion
Spin–vibronic coherence drives singlet–triplet conversion
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DOI：
10.1038/s41586-023-06233-y
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发表时间：
2023-07
期刊：
影响因子：
64.8
通讯作者：
Shahnawaz Rafiq;Nicholas P. Weingartz;Sarah Kromer;F. Castellano;Lin X. Chen
中科院分区：
文献类型：
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作者：
Shahnawaz Rafiq;Nicholas P. Weingartz;Sarah Kromer;F. Castellano;Lin X. Chen
在分子和材料化学中，对具有不同自旋多重性的激发电子态之间的跃迁的设计特定控制是极其重要的。以前的研究表明，自旋轨道和振动效应的组合，统称为自旋-振动效应，可以加速量子力学禁戒跃迁在非绝热交叉，。然而，很难确定自旋振动机制的精确实验表现。在这里，我们提出了相干光谱实验，揭示了自旋，电子和振动自由度，驱动高效的单重态-三重态转换在四个结构相关的双核Pt（II）金属-金属-配体电荷转移（MMLCT）配合物之间的相互作用。光激发激活Pt-Pt键的形成，发射伸缩振动波包。这个波包的分子结构相关的退相干和重相干动力学解决了自旋振动机制。我们发现，矢量运动沿着的铂-铂拉伸坐标调谐的单重态和中间态的能隙不可逆地朝向圆锥形的交叉点，并随后驱动形成的最低稳定的三重态中的棘轮方式。这项工作证明了使用振动相干作为探针的可行性，-澄清自旋，电子和核动力学之间的相互作用，在自旋转换过程中，这可能会激发新的模块化设计，以定制激发态的属性。
Design-specific control over the transitions between excited electronic states with different spin multiplicities is of the utmost importance in molecular and materials chemistry, –. Previous studies have indicated that the combination of spin–orbit and vibronic effects, collectively termed the spin–vibronic effect, can accelerate quantum-mechanically forbidden transitions at non-adiabatic crossings,. However, it has been difficult to identify precise experimental manifestations of the spin–vibronic mechanism. Here we present coherence spectroscopy experiments that reveal the interplay between the spin, electronic and vibrational degrees of freedom that drive efficient singlet–triplet conversion in four structurally related dinuclear Pt(II) metal–metal-to-ligand charge-transfer (MMLCT) complexes. Photoexcitation activates the formation of a Pt–Pt bond, launching a stretching vibrational wavepacket. The molecular-structure-dependent decoherence and recoherence dynamics of this wavepacket resolve the spin–vibronic mechanism. We find that vectorial motion along the Pt–Pt stretching coordinates tunes the singlet and intermediate-state energy gap irreversibly towards the conical intersection and subsequently drives formation of the lowest stable triplet state in a ratcheting fashion. This work demonstrates the viability of using vibronic coherences as probes, , –to clarify the interplay among spin, electronic and nuclear dynamics in spin-conversion processes, and this could inspire new modular designs to tailor the properties of excited states.