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 ab initio 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.

中文翻译：

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花青染料 Cy3 中激子耦合的精确建模

分子中激子耦合的准确建模对于推断耦合系统的结构和动力学非常重要。Cy3 是一种花青染料，广泛用于分子光谱学。其良好分离的激发带、对周围环境的高灵敏度和高能量转移效率使其成为激子耦合实验的理想选择。许多方法已被用于以不同程度的准确度模拟分子中的激子耦合。原子跃迁电荷模型为计算激子耦合提供了一种高精度且经济高效的方法。这项工作的主要重点是产生高质量的原子跃迁电荷，可以准确地模拟 Cy3 染料的跃迁密度。地面激发到第一激发态的跃迁密度是使用配置相互作用单项和时间相关密度泛函理论计算的，并以代数图解构造方法为基准。使用跃迁密度，我们使用两种方法推导出原子跃迁电荷：Mulliken 布居分析和适合跃迁静电势的电荷。检查电荷的质量，并通过与人工双花青结构的实验数据进行比较来评估它们准确计算激子耦合的能力。与超分子的理论比较 使用跃迁密度，我们使用两种方法推导出原子跃迁电荷：Mulliken 布居分析和适合跃迁静电势的电荷。检查电荷的质量，并通过与人工双花青结构的实验数据进行比较来评估它们准确计算激子耦合的能力。与超分子的理论比较 使用跃迁密度，我们使用两种方法推导出原子跃迁电荷：Mulliken 布居分析和适合跃迁静电势的电荷。检查电荷的质量，并通过与人工双花青结构的实验数据进行比较来评估它们准确计算激子耦合的能力。与超分子的理论比较还进行了从头算耦合和广泛使用的点偶极子近似。结果表明，使用跃迁静电势是产生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对 Cy3 染料二聚体激子耦合进行建模。