Self-assembly of multi-stranded perylene dye J-aggregates in columnar liquid-crystalline phases

Stefanie Herbst,Bartolome Soberats,Matthias Lehmann,Pawaret Leowanawat,Frank Würthner,Matthias Stolte

doi:10.1038/s41467-018-05018-6

Stefanie Herbst, Bartolome Soberats + Show 4 more

Open Access

https://doi.org/10.1038/s41467-018-05018-6

Copy DOI

Abstract

Many discoid dyes self-assemble into columnar liquid-crystalline (LC) phases with packing arrangements that are undesired for photonic applications due to H-type exciton coupling. Here, we report a series of crystalline and LC perylene bisimides (PBIs) self-assembling into single or multi-stranded (two, three, and four strands) aggregates with predominant J-type exciton coupling. These differences in the supramolecular packing and optical properties are achieved by molecular design variations of tetra-bay phenoxy-dendronized PBIs with two N–H groups at the imide positions. The self-assembly is driven by hydrogen bonding, slipped π–π stacking, nanosegregation, and steric requirements of the peripheral building blocks. We could determine the impact of the packing motifs on the spectroscopic properties and demonstrate different J- and H-type coupling contributions between the chromophores. Our findings on structure–property relationships and strong J-couplings in bulk LC materials open a new avenue in the molecular engineering of PBI J-aggregates with prospective applications in photonics.

Highlights

Many discoid dyes self-assemble into columnar liquid-crystalline (LC) phases with packing arrangements that are undesired for photonic applications due to H-type exciton coupling
These results are of great importance for the fine-tuning of properties of tailor-made materials for photonic applications as it was recently demonstrated for MEHPBI in imprinted LC pillar microcavities[39]
The basic structure of the perylene bisimides (PBIs) compounds consists of a 1,6,7,12-tetraphenoxy PBI with four dendrons attached to the phenoxy spacers and two unblocked NHs at the imide positions (Fig. 1a)

Summary

Introduction

Many discoid dyes self-assemble into columnar liquid-crystalline (LC) phases with packing arrangements that are undesired for photonic applications due to H-type exciton coupling. We report a series of crystalline and LC perylene bisimides (PBIs) self-assembling into single or multi-stranded (two, three, and four strands) aggregates with predominant J-type exciton coupling These differences in the supramolecular packing and optical properties are achieved by molecular design variations of tetra-bay phenoxy-dendronized PBIs with two N–H groups at the imide positions. The twist in the PBI cores and the steric demand of the dendrons play a key role in the columnar assembly modes, which in turn have an impact on the exciton couplings between dyes and on spectroscopic properties such as absorption and emission maxima of the J-aggregates These results are of great importance for the fine-tuning of properties of tailor-made materials for photonic applications as it was recently demonstrated for MEHPBI in imprinted LC pillar microcavities[39]

Objectives

Methods

Results

Conclusion