Institut für Organische Chemie, Center for Nanosystems Chemistry & Bavarian Polymer Institute, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
Acc Chem Res. 2021 Feb 2;54(3):642-653. doi: 10.1021/acs.accounts.0c00590. Epub 2020 Dec 8.
The discovery of the self-assembly of cyanine dyes into J-aggregates had a major impact on the development of dye chemistry due to the emergence of new useful properties in the aggregated state. The unique optical features of these J-aggregates are narrowed, bathochromically shifted absorption bands with almost resonant fluorescence with an increased radiative rate that results from the coherently coupled molecular transition dipoles arranged in a slip-stacked fashion. Because of their desirable properties, J-aggregates gained popularity in the field of functional materials and enabled the efficient photosensitization of silver halide grains in color photography. However, despite a good theoretical understanding of structure-property relationships by the molecular exciton model, further examples of J-aggregates remained scarce for a long time as supramolecular designs to guide the formation of dye aggregates into the required slip-stacked arrangement were lacking.Drawing inspiration from the bacteriochlorophyll self-organization found in the chlorosomal light-harvesting antennas of green sulfur bacteria, we envisioned the use of nature's supramolecular blueprint to develop J-aggregates of perylene bisimides (PBIs). This class of materials is applied in high-performance color pigments and as n-type organic semiconductors in transistors and solar cells. Combining outstanding photochemical and thermal stability, high tinctorial strength and excellent fluorescence, PBIs are therefore an ideal model system for the preparation of J-aggregates with a wide range of potential applications.In this Account, we elucidate how a combination of steric constraints and hydrogen bonding receptor sites can guide the self-assembly of PBI dyes into slip-stacked packing motifs with J-type exciton coupling. We will discuss the supramolecular polymerization of multiple hydrogen-bonded PBI strands in organic and aqueous media and how minor structural modifications in monomeric PBI molecules can be used to obtain near-infrared absorbing J-aggregates, organogels, or thermoresponsive hydrogels. Pushing the boundaries of self-assembly into the bulk, engineering of the substituents' steric requirements by a dendron-wedge approach afforded adjustable numbers of helical strands of PBI J-aggregates in the columnar liquid-crystalline state and the preparation of lamellar phases. To fully explore their potential, we have studied PBI J-aggregates in collaborative work with spectroscopists, physicists, and theoreticians. In this way, exciton migration over distances of up to 180 nm was shown, and insights into the influence of static disorder on the transport of excitation energy in PBI J-aggregates were derived. Furthermore, the application of PBI J-aggregates as functional materials was demonstrated in photonic microcavities, thin-film transistors, and organic solar cells.
吖啶染料自组装成 J-聚集体的发现对染料化学的发展产生了重大影响，因为在聚集态中出现了新的有用性质。这些 J-聚集体具有独特的光学性质，其吸收带变窄，红移，荧光近乎共振，辐射率增加，这是由于以滑动堆叠方式排列的相干耦合分子跃迁偶极子。由于其理想的性质，J-聚集体在功能材料领域得到了广泛的应用，并能够有效地敏化彩色摄影中的银卤化物颗粒。然而，尽管通过分子激子模型对结构-性质关系有很好的理论理解，但由于缺乏引导染料聚集体形成所需滑动堆叠排列的超分子设计，很长一段时间内 J-聚集体的例子仍然很少。从绿硫细菌的菌叶绿素自组织中得到启发，我们设想利用自然的超分子蓝图来开发苝二酰亚胺（PBI）的 J-聚集体。这类材料应用于高性能彩色颜料，并作为晶体管和太阳能电池中的 n 型有机半导体。PBI 具有出色的光化学和热稳定性、高着色强度和优异的荧光，因此是制备具有广泛潜在应用的 J-聚集体的理想模型体系。
在本报告中，我们阐明了如何通过空间位阻和氢键受体结合来引导 PBI 染料自组装成具有 J 型激子耦合的滑动堆叠堆积模式。我们将讨论在有机和水介质中多氢键 PBI 链的超分子聚合，以及如何通过在单体 PBI 分子中进行微小的结构修饰来获得近红外吸收 J-聚集体、有机凝胶或温敏水凝胶。通过将自组装推向体相，通过树突-楔形方法设计取代基的空间位阻要求，可以在柱状液晶状态下获得具有可调数量螺旋 PBI J-聚集体的棒状纤维，并制备层状相。为了充分挖掘它们的潜力，我们与光谱学家、物理学家和理论家合作研究了 PBI J-聚集体。通过这种方式，证明了激子在长达 180nm 的距离上的迁移，并得出了关于静态无序对 PBI J-聚集体中激发能输运影响的见解。此外，还展示了 PBI J-聚集体作为功能材料在光子微腔、薄膜晶体管和有机太阳能电池中的应用。
