2023-07-19 アルゴンヌ国立研究所(ANL)
◆しかし、最近の研究では、特定の分子においてこの仮定が崩れ、核と電子の動態が密接に関連していることが示されました。この発見は、太陽エネルギー変換やエネルギー生産、量子情報科学などに応用できる分子の設計に影響を及ぼす可能性があります。
◆研究チームは、短時間のレーザーパルスを用いて、分子内の核と電子の動きをリアルタイムで追跡し、スピン-振動効果という現象が分子の電子ダイナミクスに影響を与えることを明らかにしました。この洞察は、光エネルギーと物質の相互作用に基づく太陽電池、電子ディスプレイ、医療治療などの分野で役立つかもしれません。
＜関連情報＞
- https://www.anl.gov/article/unveiling-the-quantum-dance-experiments-reveal-nexus-of-vibrational-and-electronic-dynamics
- https://www.nature.com/articles/s41586-023-06233-y
- https://onlinelibrary.wiley.com/doi/10.1002/anie.202304615
スピン-振動コヒーレンスが一重項-三重項変換を駆動する Spin–vibronic coherence drives singlet–triplet conversion
Shahnawaz Rafiq,Nicholas P. Weingartz,Sarah Kromer,Felix N. Castellano & Lin X. Chen
Nature Published:19 July 2023
DOI:https://doi.org/10.1038/s41586-023-06233-y
Abstract
Design-specific control over the transitions between excited electronic states with different spin multiplicities is of the utmost importance in molecular and materials chemistry1,2,3. 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 crossings4,5. 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 probes6,7,8,9 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.
ポテンシャルエネルギー曲面上の励起状態の軌跡を原子レベルの分解能でリアルタイムに明らかにする Revealing Excited-State Trajectories on Potential Energy Surfaces with Atomic Resolution in Real Time
Denis Leshchev, Andrew J. S. Valentine, Pyosang Kim, Alexis W. Mills, Subhangi Roy, Arnab Chakraborty, Elisa Biasin, Kristoffer Haldrup, Darren J. Hsu, Matthew S. Kirschner, Dolev Rimmerman, Matthieu Chollet, J. Michael Glownia, Tim B. van Driel, Felix N. Castellano, Xiaosong Li, Lin X. Chen
Angewandte Chemie International Edition Published: 28 April 2023
DOI:https://doi.org/10.1002/anie.202304615
Graphical Abstract
Excited-state trajectories of a diplatinum complex featuring photo-activated metal–metal σ-bond formation and its stretching vibrations were detected in real time by femtosecond wide-angle X-ray solution scattering. Two key coordinates for intersystem crossing were the Pt−Pt distance and the ligand orientation, along which the excited-state trajectories can be projected onto the calculated potential energy surfaces of the excited states.
Abstract
Photoexcited molecular trajectories on potential energy surfaces (PESs) prior to thermalization are intimately connected to the photochemical reaction outcome. The excited-state trajectories of a diplatinum complex featuring photo-activated metal–metal σ-bond formation and associated Pt−Pt stretching motions were detected in real time using femtosecond wide-angle X-ray solution scattering. The observed motions correspond well with coherent vibrational wavepacket motions detected by femtosecond optical transient absorption. Two key coordinates for intersystem crossing have been identified, the Pt−Pt bond length and the orientation of the ligands coordinated with the platinum centers, along which the excited-state trajectories can be projected onto the calculated PESs of the excited states. This investigation has gleaned novel insight into electronic transitions occurring on the time scales of vibrational motions measured in real time, revealing ultrafast nonadiabatic or non-equilibrium processes along excited-state trajectories involving multiple excited-state PESs.
