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The Aggregation Units of J-Aggregates: Transitioning from Monomers to Hydrogen-Bonded Dimers
Yingnan Xu1, Yang Zhao2, Huaxin Zhu1
1State Key Laboratory of Fine Chemicals, Department of Polymer Science & Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China.
Abstract:
In recent years, J-aggregates, as supramolecular assembly structures, have increasingly attracted scientific interest. Currently, the prevailing consensus is that J-aggregates are formed through the interleaved stacking of monomers arranged in parallel. However, our findings suggest that the fundamental units constituting J-aggregates are not limited to monomers alone but also encompass molecular aggregates interconnected by noncovalent bonds, which we designate as aggregation units. We have synthesized three asymmetric pyrrolopyrrole cyanine (PPCy) dyes capable of forming hydrogen-bonded dimers and have verified that these hydrogen-bonded dimers can serve as aggregation units to generate J-aggregates. The detailed structural and optical properties revealed that the J-aggregates of these dyes exhibited a significantly red-shifted and narrowed emission in the near-infrared (NIR) fluorescence compared to the monomers.
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