AI Article Synopsis
- The study investigates electron-transfer rates in donor-bridge-acceptor compounds with varying reaction free energies using transient absorption spectroscopy.
- In compounds with low driving force, electron-transfer rates decrease as the distance between donor and acceptor increases, while higher driving forces show a surprising increase in rates with distance over a certain range.
- This behavior is attributed to weak electronic coupling and increasing reorganization energy, highlighting that strongly exergonic electron transfers may behave differently than typically studied weakly exergonic reactions.
Article Abstract
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.
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| http://dx.doi.org/10.1021/acs.inorgchem.8b02973 | DOI Listing |
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