Solvent‐Induced Self‐Assembly of Naphthalenediimide Conjugated to Tetraphenylethene through D‐ and L‐Alanine

RAFT-synthesis and self-assembly-induced emission of pendant diphenylalanine-tetraphenylethylene copolymers

Manipulation of the properties of aggregation-induced emission luminogens (AIEgens) by combining self-assembling motifs has attracted significant interest as a promising approach to developing various advanced materials. In this study, pendant diphenylalanine-tetraphenylethylene (TPE) copolymers exhibiting the ability for self-assembly and AIE properties were synthesized via reversible addition-fragmentation chain-transfer (RAFT) copolymerization. The resulting anionic and non-ionic amphiphilic copolymers with a carbon-carbon main chain bearing diphenylalanine-TPE through-space interactions self-assembled into nanorods and nanofibers, showing blue emissions originating from the aggregation of TPE side chains in the assembled structures. Suitable tuning of the comonomer composition, monomer structure, and environmental conditions (e.g., solvent polarity) enables manipulation of the self-assembled structures, AIE properties, and aggregation-induced circular dichroism by achiral TPE units via through-space interactions with diphenylalanine moieties.

Synthesis and self-assembly of a diphenylalanine–tetraphenylethylene hybrid monomer and RAFT polymers with aggregation-induced emission

A hybrid monomer consisting of diphenylalanine with the self-assembling ability and tetraphenylethylene with aggregation-induced emission properties was synthesized and employed for reversible addition–fragmentation chain transfer polymerization.

Solvent-Directed Transformation of the Self-assembly and Optical Property of a Peptide-Appended Core-Substituted Naphthelenediimide and Selective Detection of Nitrite Ions in an Aqueous Medium

This study vividly displays the different self-assembling behavior and consequent tuning of the fluorescence property of a peptide-appended core-substituted naphthalenediimide (N1) in the aliphatic hydrocarbon solvents (n-hexane/n-decane/methyl cyclohexane) and in an aqueous medium within micelles. The N1 is highly fluorescent in the monomeric state and self-aggregates in a hydrocarbon solvent, exhibiting "H-type" or "face-to-face" stacking as indicated by a blue shift of absorption maxima in the UV-vis spectrum. In the H-aggregated state, the fluorescence emission of N1 changes to green from the yellow emission obtained in the monomeric state. In the presence of a micelle-forming surfactant, cetyl trimethylammonium bromide (CTAB), the N1 is found to be dispersed in a water medium. Interestingly, upon encapsulation of N1 into the micelle, the molecule alters its self-assembling pattern and optical property compared to its behavior in the hydrocarbon solvent. The N1 exhibits "edge-to-edge" stacking or J aggregates inside the micelle as indicated by the UV-vis spectroscopic study, which shows a red shift of the absorption maxima compared to that in the monomeric state. The fluorescence emission also differs in the water medium with the NDI derivative exhibiting red emission. FT-IR studies reveal that all amide NHs of N1 are hydrogen-bonded within the micelle (in the J-aggregated state), whereas both non-bonding and hydrogen-bonding amide NHs are present in the H-aggregated state. This is a wonderful example of solvent-mediated transformation of the aggregation pattern (from H to J) and solvatochromism of emission over a wide range from green in the H-aggregated state to yellow in the monomeric state and orangish-red in the J-aggregated state. Moreover, the J aggregate has been successfully utilized for selective and sensitive detection of nitrite ions in water even in the presence of other common anions (NO₃^-, SO₄^2-, HSO₄^-, CO₃^2-, and Cl^-).

Tuning Achiral to Chiral Supramolecular Helical Superstructures

The design and synthesis of achiral organic functional molecules which can assemble into a chiral with selective handedness in the absence of chiral substances is an important in understanding the role chirality plays within these systems. In this review, we described general approaches towards supramolecular chiral molecules the synthesis and self-assembly of achiral molecule to active chiral molecules to investigate controlled supramolecular chiral nanostructures with their photoluminescent properties for rapid, sensitive and selective detection of analytes of choice. Various small molecules have been discussed for achiral to chiral along with induction of chirality and controlled chiral helical structures in detail. We discussed few examples where stimuli used to control the chirality such as temperature, pH etc. Finally, we will also explore on the photo responsive helicity properties of the aggregation induced emission active molecule such as tetraphenylethene conjugates.