Through continuous efforts in developing a new class of foldamers, homogeneous sulfono-γ-AApeptides have been designed and synthesized using tetraphenylethylene (TPE) moieties attached to the backbone as luminogenic sidechains. Based on previous crystal structures, it is found that these foldamers adopted a left-handed 414-helix. Due to the constraint of the helical scaffold, the rotation of the TPE moieties is restricted, leading to fluorescent emissive properties with high quantum yields not only at the aggregate state but also in solution. Investigation of the relationship between the structure and fluorescence behavior reveals that emission is induced by the combined effect of the aggregation-induced emission and the rotated restriction from the backbone. Furthermore, as the packing mode of the luminogens can be precisely adjusted by the helical backbone, these foldamers are found to be circularly polarizable with relatively large luminescence dissymmetry factor. Interestingly, possessing cationic amphipathic structures similar to that of host-defense peptides, these sulfono-γ-AApeptides are able to inhibit the growth of Gram-positive bacteria, methicillin-resistant Staphylococcus aureus through membrane interactions.
- aggregation-induced emission
- circularly-polarized luminescence
- helical conformation