Helical Sulfono-γ-AApeptides with Aggregation-Induced Emission and Circularly Polarized Luminescence

Aggregation-induced emission (AIE)
was intensively studied because
of packing of small molecules and polymers; however, mid-molecular-weight
(1000–3000) molecular scaffold containing a precise number
of AIE luminogens is rare. Herein, we report the investigation of
three tetraphenylethylene (TPE)-modified sulfono-γ-AApeptides
in which multiple TPE moieties are conjugated to the chiral right-handed
helical peptidomimetic backbone as functional side chains. The crystal
structure of the TPE-α/sulfono-γ-AA peptide 1 demonstrates that because of the rigid helical scaffold of the TPE-α/sulfono-γ-AA
peptides, the intramolecular rotations of the TPE with short linker
are restricted, therefore leading to the boosted fluorescent emission
in solution. Peptides 2 and 3 exhibit aggregation-induced
emission enhancement (AIEE), possibly because of the combination of
both AIE and rotation restriction. Moreover, because of their preoriented
assembly induced by the right-handed helical scaffold, these emissive
chiral luminogens show effective circularly polarized luminescence
signals with high dissymmetry factor glum. Finally, the amphiphilic nature of TPE-α/sulfono-γ-AA
peptides could enable them to penetrate the bacterial membranes and
exhibit strong fluorescence. Their antimicrobial activity and labeling-free
character could further augment their potential applications in both
materials and biomedical sciences.