Titov Evgenii
Theoretical Chemistry, Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany.
Molecules. 2021 Jul 13;26(14):4245. doi: 10.3390/molecules26144245.
Azobenzene-containing molecules may associate with each other in systems such as self-assembled monolayers or micelles. The interaction between azobenzene units leads to a formation of exciton states in these molecular assemblies. Apart from local excitations of monomers, the electronic transitions to the exciton states may involve charge transfer excitations. Here, we perform quantum chemical calculations and apply transition density matrix analysis to quantify local and charge transfer contributions to the lowest electronic transitions in azobenzene dimers of various arrangements. We find that the transitions to the lowest exciton states of the considered dimers are dominated by local excitations, but charge transfer contributions become sizable for some of the lowest ππ* electronic transitions in stacked and slip-stacked dimers at short intermolecular distances. In addition, we assess different ways to partition the transition density matrix between fragments. In particular, we find that the inclusion of the atomic orbital overlap has a pronounced effect on quantifying charge transfer contributions if a large basis set is used.
含偶氮苯的分子可能会在诸如自组装单分子层或胶束等体系中相互缔合。偶氮苯单元之间的相互作用会导致在这些分子聚集体中形成激子态。除了单体的局部激发外，向激子态的电子跃迁可能涉及电荷转移激发。在此，我们进行量子化学计算并应用跃迁密度矩阵分析，以量化各种排列的偶氮苯二聚体中局部和电荷转移对最低电子跃迁的贡献。我们发现，所考虑的二聚体向最低激子态的跃迁主要由局部激发主导，但在短分子间距离下，对于堆叠和滑移堆叠二聚体中的一些最低ππ*电子跃迁，电荷转移贡献变得相当可观。此外，我们评估了在片段之间划分跃迁密度矩阵的不同方法。特别是，我们发现，如果使用大基组，原子轨道重叠的包含对量化电荷转移贡献有显著影响。
