Ten-Fold Solvent Kinetic Isotope Effect for the Nonradiative Relaxation of the Aqueous Ferrate(VI) Ion
Ten-Fold Solvent Kinetic Isotope Effect for the Nonradiative Relaxation of the Aqueous Ferrate(VI) Ion
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DOI：
10.1021/acs.jpca.3c06042
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发表时间：
2023-11-29
影响因子：
2.9
通讯作者：
Hayes，Dugan
中科院分区：
文献类型：
--
作者：
Antolini，Cali;Jacoby，Danielle J.;Hayes，Dugan
高价铁中间体已经在许多金属蛋白的催化循环中被调用，因此，了解这些物种与其环境之间的耦合如何影响其化学和物理性质是至关重要的。在这项工作中，我们利用溶剂动力学同位素效应（SKIE）的洞察到非辐射失活的电子激发态的水溶液中的高铁酸盐（VI）离子。我们观察到一个非常大的SKIE为9.7纳秒尺度的最低能量的三重态配体场态的基态弛豫。质子库存研究表明，一个单一的溶剂O-H键耦合到离子在失活过程中，可能是由于稀疏的振动结构的高铁酸盐（VI）。这样的机制是一致的，为三价镧系元素的水溶液，表现出极大的SKIE值的失活off-fexcited状态的报告。这种现象完全归因于能量耗散到溶剂受体模式的更高泛音中，因为由于溶剂粘度的变化对表观弛豫速率的任何影响可以忽略不计。
Hypervalent iron intermediates have been invoked in the catalytic cycles of many metalloproteins, and thus, it is crucial to understand how the coupling between such species and their environment can impact their chemical and physical properties in such contexts. In this work, we take advantage of the solvent kinetic isotope effect (SKIE) to gain insight into the nonradiative deactivation of electronic excited states of the aqueous ferrate(VI) ion. We observe an exceptionally large SKIE of 9.7 for the nanosecond-scale relaxation of the lowest energy triplet ligand field state to the ground state. Proton inventory studies demonstrate that a single solvent O–H bond is coupled to the ion during deactivation, likely due to the sparse vibrational structure of ferrate(VI). Such a mechanism is consistent with that reported for the deactivation off–fexcited states of aqueous trivalent lanthanides, which exhibit comparably large SKIE values. This phenomenon is ascribed entirely to dissipation of energy into a higher overtone of a solvent acceptor mode, as any impact on the apparent relaxation rate due to a change in solvent viscosity is negligible.