Transition energies of benzoquinone anions are immune to symmetry breaking by a single water molecule.
Transition energies of benzoquinone anions are immune to symmetry breaking by a single water molecule.
复制标题
苯醌阴离子的跃迁能不受单个水分子对称性破坏的影响。
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
S. Nielsen
中科院分区：
文献类型：
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作者：
M. Stockett;S. Nielsen
对苯二酚是对苯二酚类分子中的典型成员，具有与光合作用初级反应相关的基本功能。由于在近共振电子转移过程中形成了电子激发的苯醌阴离子，关键问题是局域环境如何影响激发态能级和去激发时间。前者我们用真空中分离的质量选择裸阴离子(Pbq(-))和一水Pbq(-)·H2O络合物的作用光谱进行了讨论。该络合物代表了内部质子转移的前驱物质，形成了光驱动电子传递链中的第一个化学产物--半喹酮自由基。这两个离子在可见光和紫外光中都显示出谱带，重要的是，它们的最大值几乎相同。尽管负电荷局部化，从而破坏了高轨道对称性，但水令人惊讶地是无害的。这一发现表明，对苯二酚微环境的自然波动只会导致激发态能量的微小变化，从而导致电子转移速率的变化。因此，对苯二酚是电子传递的强健参与者。
p-Benzoquinone is the prototypical member of the quinone class of molecules with a basic functionality relevant for the primary reactions of photosynthesis. As electronically excited quinone anions are formed in near-resonant electron transfer, key issues are how the local environment affects excited-state energy levels and deexcitation times. The former we address here with action spectroscopy of mass-selected bare radical anions (pBQ(-)) and one-water pBQ(-)·H2O complexes, isolated in vacuo. The complex represents a precursor for internal proton transfer to form the semiquinone free radical, the first chemical product in the light-driven electron transport chain. Both ions display bands in the visible and ultraviolet with, importantly, almost identical maxima. Despite localizing negative charge, thereby breaking the high orbital symmetries, water is surprisingly innocent. This finding implies that natural fluctuations in the quinone microenvironment cause only minor variations in excited-state energies and thus electron-transfer rates. Hence quinones are robust participants in electron transport.