Development of circularly
polarized luminescent (CPL) materials
with strong emission and high dissymmetry factor of luminescence (g
lum) is highly desirable. A series of CPL-active
aggregation-induced emission luminogens (AIEgens) have been successfully
constructed by incorporating AIEgen dicyanodistyrylbenzene (DCS) into
chiral molecule cholesterol. Benefiting from its typical AIE characteristic,
DCS allows emission efficiency up to 73.7% in a condensed state. Furthermore,
cholesterol units ensure forming chiral liquid crystal in syntax,
and increasing the g
lum value of CPL from
7 × 10–4 for the amorphous state to 1.1 ×
10–1 for the liquid crystal state. This approach
paves a general avenue for addressing the major defect well: high g
lum always suffers from suppression of emission
efficiency.
A luminescent liquid
crystal molecule (TPEMes) with efficient solid-state
emission is rationally constructed via the chemical conjugation of
blue-emitting tetraphenylethene cores and luminescent mesogenic tolane
moieties, which are both featured with aggregation-induced emission
properties. As for this fluorophore, aggregation-induced energy transfer
from the emissive tolane mesogens to the lighting-up tetraphenylethene
units endows the molecule pure blue emission in the suspension and
bulk state. Combining differential scanning calorimetry, polarized
optical microscope, and one-dimensional X-ray diffraction (1D XRD)
experiments, the compound TPEMes is deduced to adapt thermodynamically
more stable layered crystalline phase and can be “frozen”
into a monotropic smectic mesophase due to kinetic reasons. As a result
of more dense packing of TPEMes in the crystalline phase indicated
by 1D XRD, the luminescence of TPEMes in crystalline phase blue-shifted
by 17 nm relative to the metastable mesophase.
Precisely controlling the circularly polarized emission of achiral organic luminescent molecules in an aggregated state is a remaining challenge in this research field, since it should simultaneously overcome the ubiquitous issues of chirality transfer and aggregation‐caused quenching occurring in the aggregated systems. Herein, a facile and universal approach to achieving assembly‐accelerated photocyclization and photocyclization‐enhanced emission of tetraphenylethylene (TPE) derivative in the gel state is reported. This experimental data reveal that the co‐assembled gels exhibit high efficiency of photocyclization (≥100 times more efficient than the TPE‐based derivative in solution) via the hydrogen‐bonding‐driven helical assembly, displaying sharply enhanced emission (with the maximum enhancement of 105 times) after the photocyclization and oxidation under ultraviolet irradiation. Furthermore, inverted circularly polarized luminescence (CPL) is achieved after the photocyclization of TPE‐based gels. The strategy of assembly‐enhanced emission and photomodulated CPL inversion of fluorescent organic systems in the aggregated state can increase the abundance of chiral luminescent soft matters, leading to versatile applications in organic chiroptical optoelectronics and smart flexible displaying devices.
A temperature-sensitive Förster resonance energy transfer system was constructed using a highly emissive liquid crystal co-assembled with Nile red, enabling thermo-optical modulation for controlling and directing light in stimuli-responsive devices.
The study of dynamic supramolecular chirality inversion
(SMCI)
not only helps to deepen the understanding of chiral transfer and
amplification in both living organizations and artificially chemical
self-assembly systems but also is useful for the development of smart
chiral nanomaterials. However, it is still challenging to achieve
the dynamic SMCI of the self-aggregation of metal–organic supramolecular
polymers with great potential in asymmetric synthesis, chiroptical
switches, and circular polarized luminescence. Here, we successfully
developed a hierarchical coassembly system based on the mPAzPCC and various metal ions with effective chirality transfer and
temporal-controlled SMCI. Due to the dynamic self-assembly and hierarchical
chirality transfer of the Ag+/mPAzPCC
complex driven by metallophilic interaction and coordination, morphological
transition with nanoribbons, helical nanoribbons, and chiral nanotubules
was successively obtained. Interestingly, the SMCI of chiral nanoaggregates
was precisely regulated by solvents and metal ions in the Cu2+/mPAzPCC and Mn2+/mPAzPCC
system. Besides, temporal-controlled dynamic SMCI switching from helix
to bundled helix was clearly revealed in the aggregation of Cu2+/mPAzPCC, Mn2+/mPAzPCC, and Bi3+/mPAzPCC systems. This
work provides a metallophilic interaction-mediated helical assembly
pathway to dynamically modulate the chirality of metal–organic
complex-based assemblies and deepen the understanding of the hierarchically
dynamic self-assembly process, which would be of great potential in
metal ion-mediated supramolecular asymmetric catalysis and bioinspired
chiral sensing.
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