Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.
Department of Chemistry, Brandywine Campus, The Pennsylvania State University, Media, Pennsylvania 19063, United States.
J Phys Chem A. 2021 Sep 16;125(36):7852-7866. doi: 10.1021/acs.jpca.1c05556. Epub 2021 Sep 8.
Accurate modeling of excitonic coupling in molecules is of great importance for inferring the structures and dynamics of coupled systems. Cy3 is a cyanine dye that is widely used in molecular spectroscopy. Its well-separated excitation bands, high sensitivity to the surroundings, and the high energy transfer efficiency make it a perfect choice for excitonic coupling experiments. Many methods have been used to model the excitonic coupling in molecules with varying degrees of accuracy. The atomic transition charge model offers a high-accuracy and cost-effective way to calculating the excitonic coupling. The main focus of this work is to generate high-quality atomic transition charges that can accurately model the Cy3 dye's transition density. The transition density of the excitation of the ground to first excited state is calculated using configuration-interaction singles and time-dependent density functional theory and is benchmarked against the algebraic diagrammatic construction method. Using the transition density we derived the atomic transition charges using two approaches: Mulliken population analysis and charges fitted to the transition electrostatic potential. The quality of the charges is examined, and their ability to accurately calculate the excitonic coupling is assessed via comparison to experimental data of an artificial biscyanine construct. Theoretical comparisons to the supermolecule couplings and the widely used point-dipole approximation are also made. Results show that using the transition electrostatic potential is a reliable approach for generating the transition atomic charges. A high-quality set of charges, that can be used to model the Cy3 dye dimer excitonic coupling with high-accuracy and a reasonable computational cost, is obtained.
准确建模分子中的激子耦合对于推断耦合系统的结构和动力学非常重要。Cy3 是一种菁染料，广泛用于分子光谱学。其激发带分离良好、对环境高度敏感以及能量转移效率高，使其成为激子耦合实验的理想选择。许多方法已被用于对分子中的激子耦合进行建模，其准确性各有不同。原子跃迁电荷模型提供了一种高精度和具有成本效益的方法来计算激子耦合。这项工作的主要重点是生成高质量的原子跃迁电荷，以准确模拟 Cy3 染料的跃迁密度。使用组态相互作用单激发和含时密度泛函理论计算基态到第一激发态激发的跃迁密度，并与代数图构造方法进行基准测试。利用我们推导的跃迁密度，采用两种方法（Mulliken 布居分析和拟合跃迁静电势的电荷）来获得原子跃迁电荷。我们检查了电荷的质量，并通过与人工双菁构象的实验数据进行比较，评估了它们准确计算激子耦合的能力。还对超分子耦合和广泛使用的点偶极近似进行了理论比较。结果表明，使用跃迁静电势是生成跃迁原子电荷的可靠方法。获得了一组高质量的电荷，可用于以高精度和合理的计算成本来模拟 Cy3 染料二聚体的激子耦合。
