Department of Chemistry 'Giacomo Ciamician', Università di Bologna, Via F. Selmi, 2, 40126 Bologna, Italy.
Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain.
Molecules. 2023 Jun 8;28(12):4642. doi: 10.3390/molecules28124642.
The charged forms of π-conjugated chromophores are relevant in the field of organic electronics as charge carriers in optoelectronic devices, but also as energy storage substrates in organic batteries. In this context, intramolecular reorganization energy plays an important role in controlling material efficiency. In this work, we investigate how the diradical character influences the reorganization energies of holes and electrons by considering a library of diradicaloid chromophores. We determine the reorganization energies with the four-point adiabatic potential method using quantum-chemical calculations at density functional theory (DFT) level. To assess the role of diradical character, we compare the results obtained, assuming both closed-shell and open-shell representations of the neutral species. The study shows how the diradical character impacts the geometrical and electronic structure of neutral species, which in turn control the magnitude of reorganization energies for both charge carriers. Based on computed geometries of neutral and charged species, we propose a simple scheme to rationalize the small, computed reorganization energies for both n-type and p-type charge transport. The study is supplemented with the calculation of intermolecular electronic couplings governing charge transport for selected diradicals, further supporting the ambipolar character of the investigated diradicals.
带电荷的π共轭发色团在有机电子学领域很重要，它们可以作为光电设备中的电荷载流子，也可以作为有机电池中的储能基质。在这种情况下，分子内重组能在控制材料效率方面起着重要作用。在这项工作中，我们通过考虑一系列自由基发色团来研究自由基特性如何影响空穴和电子的重组能。我们使用四点绝热势能法并结合密度泛函理论（DFT）水平的量子化学计算来确定重组能。为了评估自由基特性的作用，我们比较了在中性物种的闭壳层和开壳层表示假设下获得的结果。研究表明，自由基特性如何影响中性物种的几何和电子结构，这反过来又控制了两种电荷载流子的重组能的大小。基于中性和带电物种的计算几何形状，我们提出了一个简单的方案来合理化计算出的 n 型和 p 型电荷输运的小重组能。该研究还补充了计算所选自由基的控制电荷输运的分子间电子耦合，进一步支持了所研究的自由基的双极性。
