What Makes a Strong Organic Electron Donor (or Acceptor)?
What Makes a Strong Organic Electron Donor (or Acceptor)?
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DOI：
10.1002/chem.201406597
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发表时间：
2015-06-01
影响因子：
4.3
通讯作者：
Himmel, Hans-Joerg
中科院分区：
文献类型：
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作者：
Eberle, Benjamin;Huebner, Olaf;Himmel, Hans-Joerg
有机电子给体对于许多应用都很重要。然而，对于具有所需还原能力的化合物的定向设计所必需的因素尚不清楚。在这里，我们对这些因素进行详细分析。忽略环境的内在还原能力必须与外在（例如溶剂）影响分开。该功率可以通过气相电离能来量化。实验获得的溶液中的氧化还原电位和计算出的溶剂中的电离能（用类导体屏蔽模型（COSMO）建模）包括内在因素和外在因素。有机电子给体共轭体系的增加导致本征还原能力的增加，但也降低了溶剂稳定性。因此，内在效应和外在效应是相互竞争的。一般来说，外在影响占主导地位。我们提出了溶液中氧化还原电位与气相电离能和有机电子供体体积之间的简单关系。我们最终得出了一些公式，可以根据溶液中测量的氧化还原电位来估计电子供体的（气相）电离能或电子受体的（气相）电子亲和力。该公式可用于没有或只有很小的静态偶极矩且氧化/还原后电荷分布相对均匀的中性有机分子。
Organic electron donors are of importance for a number of applications. However, the factors that are essential for a directed design of compounds with desired reduction power are not clear. Here, we analyze these factors in detail. The intrinsic reduction power, which neglects the environment, has to be separated from extrinsic (e.g., solvent) effects. This power could be quantified by the gas-phase ionization energy. The experimentally obtained redox potentials in solution and the calculated ionization energies in a solvent (modeled with the conductor-like screening model (COSMO)) include both intrinsic and extrinsic factors. An increase in the conjugated -system of organic electron donors leads to an increase in the intrinsic reduction power, but also decreases the solvent stabilization. Hence, intrinsic and extrinsic effects compete against each other; generally the extrinsic effects dominate. We suggest a simple relationship between the redox potential in solution and the gas-phase ionization energy and the volume of an organic electron donor. We finally arrive at formulas that allow for an estimate of the (gas-phase) ionization energy of an electron donor or the (gas-phase) electron affinity of an electron acceptor from the measured redox potentials in solution. The formulas could be used for neutral organic molecules with no or only small static dipole moment and relatively uniform charge distribution after oxidation/reduction.