Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Frankfurt, 60438, Germany.
Department of Chemical System Engineering, The University of Tokyo, Tokyo, 113-8656, Japan.
Nat Commun. 2018 Oct 29;9(1):4502. doi: 10.1038/s41467-018-06615-1.
Light absorption of myoglobin triggers diatomic ligand photolysis and a spin crossover transition of iron(II) that initiate protein conformational change. The photolysis and spin crossover reactions happen concurrently on a femtosecond timescale. The microscopic origin of these reactions remains controversial. Here, we apply quantum wavepacket dynamics to elucidate the ultrafast photochemical mechanism for a heme-carbon monoxide (heme-CO) complex. We observe coherent oscillations of the Fe-CO bond distance with a period of 42 fs and an amplitude of ∼1 Å. These nuclear motions induce pronounced geometric reorganization, which makes the CO dissociation irreversible. The reaction is initially dominated by symmetry breaking vibrations inducing an electron transfer from porphyrin to iron. Subsequently, the wavepacket relaxes to the triplet manifold in ∼75 fs and to the quintet manifold in ∼430 fs. Our results highlight the central role of nuclear vibrations at the origin of the ultrafast photodynamics of organometallic complexes.
肌红蛋白的光吸收会引发双原子配体光解和铁(II)的自旋交叉跃迁，从而引发蛋白质构象变化。光解和自旋交叉反应在飞秒时间尺度上同时发生。这些反应的微观起源仍存在争议。在这里，我们应用量子波包动力学阐明了血红素-一氧化碳（heme-CO）络合物的超快光化学机制。我们观察到 Fe-CO 键距离的相干振荡，其周期为 42 fs，幅度约为 1 Å。这些核运动引起明显的几何重排，使 CO 解离不可逆。该反应最初由对称破缺振动主导，导致电子从卟啉转移到铁。随后，波包在约 75 fs 内弛豫到三重态，在约 430 fs 内弛豫到五重态。我们的结果强调了核振动在金属有机配合物超快光动力学中的核心作用。
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