Molecular excitons play a central role in natural and artificial light harvesting, organic electronics, and nanoscale computing. The structure and dynamics of molecular excitons, critical to each application, are sensitively governed by molecular packing. Deoxyribonucleic acid (DNA) templating is a powerful approach that enables controlled aggregation via sub-nanometer positioning of molecular dyes. However, finer sub-Angstrom control of dye packing is needed to tailor excitonic properties for specific applications. Here, we show that adding rotaxane rings to squaraine dyes templated with DNA promotes an elusive oblique packing arrangement with highly desirable optical properties. Specifically, dimers of these squaraine:rotaxanes exhibit an absorption spectrum with near-equal intensity excitonically split absorption bands. Theoretical analysis indicates that the transitions are mostly electronic in nature and only have similar intensities over a narrow range of packing angles. Compared with squaraine dimers, squaraine:rotaxane dimers also exhibit extended excited-state lifetimes and less structural heterogeneity. The approach proposed here may be generally useful for optimizing excitonic materials for a variety of applications ranging from solar energy conversion to quantum information science.

分子激子在自然和人造光收集、有机电子学和纳米级计算中发挥着核心作用。分子激子的结构和动力学对于每种应用都至关重要，并且受到分子堆积的敏感控制。脱氧核糖核酸 (DNA) 模板是一种强大的方法，可通过分子染料的亚纳米定位实现受控聚集。然而，需要对染料堆积进行更精细的亚埃控制，以便为特定应用定制激子性能。在这里，我们证明，在以 DNA 为模板的方酸菁染料中添加轮烷环可促进难以捉摸的倾斜堆积排列，并具有非常理想的光学特性。具体来说，这些方酸：轮烷的二聚体表现出具有几乎相等强度的激子分裂吸收带的吸收光谱。理论分析表明，跃迁本质上主要是电子跃迁，并且仅在狭窄的堆积角度范围内具有相似的强度。与方酸菁二聚体相比，方酸菁：轮烷二聚体还表现出更长的激发态寿命和更少的结构异质性。这里提出的方法通常可用于优化从太阳能转换到量子信息科学等各种应用的激子材料。