Self-twisting for macrochirality from an achiral asterisk molecule with fluorescence-phosphorescence dual emission

Controlling Ultra-Large Optical Asymmetry in Amorphous Molecular Aggregations

Although ultra-large optical asymmetry appears in crystalline materials, distractions from the mesoscopic ordering often causes inauthenticity in chiropticity. In amorphous materials, however, it remains challenging and elusive to achieve large chiropticity. Herein, we report the quantitative control of chiral amplification, on amorphous supramolecular structures of cholesteryl-linked bis(dipyrrinato)zinc(II), to an exceptionally high level. A proper chiral packing of the building block at several molecular scale considerably contributes to the absorptive dissymmetry factor g_abs , although the system is overall disordered. The intense and tunable aggregation strength renders a variable g_abs value up to +0.10 and +0.31 in the solution and in film state. On this basis, a superior ON-OFF switching of chiropticity is realized under external stimuli. This work establishes a general design principle to control over ultra-large optical asymmetry on a wider scope of chiral materials.

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.

Water inversed helicity of nanostructures from ionic self-assembly of a chiral gelator and an achiral component

The ionic self-assemblies (ISAs) formed by a cationic chiral organogelator (l-glutamide amphiphile, abbreviated as PULG) and anionic dyes exhibited helical nanostructures. And the formed helical structures can be tuned by water amount in the ethanol/water solvent. In pure ethanol, the chirality of the gelator was successfully transferred to the achiral components, which was confirmed by the appearance of an induced CD signal in the achiral components. Meanwhile, the electrostatic interaction between the gelator and achiral dyes contributed to the chirality amplification, causing the nanofibrous structures of the gelator to be transformed to uniform left-handed helices. Upon adding water to ethanol, the induced CD signal exhibited inversion from positive to negative. Interestingly, the left-handed helices formed by ISA of PULG/anionic dyes in ethanol were inverted to right-handed helices with the addition of water. Based on detailed investigations of the XRD patterns, CD and UV/Vis spectra, the mechanism of helicity inversion was proposed: left-handed helices were dominated by hydrogen bonding and right-handed helices were dominated by π-π stacking. This work exemplifies a feasible method to invert the helicity of chiral nanostructures in co-assembly and gives an insight into the conformation change of biomacromolecules in a biological system.

Dynamic Modulation of Supramolecular Chirality Driven by Factors from Internal to External Levels

Supramolecular chirality, generated by the asymmetric assembly of chiral or achiral molecules, has attracted intense study owing to its potential to offer insights into natural biological structures and its crucial roles in advanced materials. The optical activity and stacking pathway of building molecules both greatly determine the chirality of the whole supramolecular structure. The flexibility of supramolecular structures makes their chirality easy to modulate through abundant means. Adjustment of the molecular structure or packing mode, or external stimuli that act like a finger gently pushing toy bricks, can greatly change the chirality of supramolecular assemblies. The dynamic regulation of chiral nanostructures on the intramolecular, intermolecular, and external levels could be regarded as the modulatory essence in numerous strategies, however, this perspective is ignored in most reviews in the literature. Herein, therefore, we focus on the ingenious dynamic modulation of chiral nanostructures by these factors. Through dynamic modulation with changes in chiroptical spectroscopy and electron microscopy, the mechanism of formation of supramolecular chirality is also elaborated.