Neumann Svenja, Wenger Oliver S
Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland.
Inorg Chem. 2019 Jan 7;58(1):855-860. doi: 10.1021/acs.inorgchem.8b02973. Epub 2018 Dec 12.
The distance dependences of electron-transfer rates ( k) in three homologous series of donor-bridge-acceptor compounds with reaction free energies (Δ G) of ca. -1.2, -1.6, and -2.0 eV for thermal charge recombination after initial photoinduced charge separation were studied by transient absorption spectroscopy. In the series with low driving force, the distance dependence is normal and k decreases upon donor-acceptor distance ( r) elongation. In the two series with higher driving forces, k increases with increasing distance over a certain range. This counterintuitive behavior can be explained by a weakly distance-dependent electronic donor-acceptor coupling ( H) in combination with an increasing reorganization energy (λ). Our study shows that highly exergonic electron transfers can have distance dependences that differ drastically from those of the more commonly investigated weakly exergonic reactions.
通过瞬态吸收光谱研究了三种供体-桥-受体化合物同系物中电子转移速率（k）与距离的依赖关系，这些化合物在初始光诱导电荷分离后的热电荷复合反应自由能（ΔG）约为-1.2、-1.6和-2.0 eV。在驱动力较低的同系物系列中，距离依赖性是正常的，并且随着供体-受体距离（r）的延长，k减小。在两个驱动力较高的同系物系列中，在一定范围内，k随距离增加而增大。这种违反直觉的行为可以通过弱距离依赖性的电子供体-受体耦合（H）与重组能（λ）增加相结合来解释。我们的研究表明，高度放能的电子转移可能具有与更常研究的弱放能反应截然不同的距离依赖性。
