Solvent-Directed Hierarchical Self-Assembly of Tetraphenylpyrazine-Cholesterol with Amplified Circularly Polarized Luminescence

Abstract

It is important to identify the effect of assembly and aggregation on the chirality transfer and energy transmission in supramolecular polymer system, since the unordered aggregation is insufficient to promote luminescence enhancement and chirality transfer, even causing the negative effect. Another key issue is to identify the solvent effect on hierarchically chiral self-assembly. Herein, we designed an AIE-core based building block, tetraphenylpyrazine-cholesterol (TPP-Chol), to explore how the solvent component influences chirality transfer and energy transmission of its aggregates and/or assemblies. Interestingly, the hierarchical assembly behavior was realized in the mixture of MeOH/CHCl 3 highly dependent on the MeOH content. During the solvent-directed hierarchical assembly, the morphologic transformations, such as nanoribbons with a width of 150 nm, twisted nanoribbons with helical pitch of 420 nm, nanoribbon clusters, and microflowers with an average diameter of 5.5 μm, were realized with obvious chirality amplification for both circular dichroism (CD) and circularly polarized luminescence (CPL) measurements. The hierarchical assembly of TPP-Chol was also demonstrated by a time-dependent CD test. The work points out the complexity and dynamic of hierarchically chiral self-assembly regulated by the solvent effect, which would be helpful for the development of supramolecular materials with enhanced CPL performance and dynamic chirality.

Self-Assembly of Functionalized Twistarenes into Supramolecular Assemblies with Chiroptical Property and Photoconductive Behavior

“…Ubiquitous self-assembly in nature exerts a crucial role for bioactivity and biofunctions. − The classical example is a double-helix structure of DNA that widely occurs in plants and animals . Beyond these, such behavior in artificial systems can provide more room to construct supramolecular micro-/nanoassemblies with tunable physical properties, endowing them with potential application in miniature devices. − Among them, the introduction of chiral elements such as stereogenic centers, chiral axles, and helicene and helical chirality into the supramolecular assemblies is favorable for unveiling the origin of homochirality and promoting the potential application in different areas such as asymmetric catalysis and chiral recognition. − In general, the highly ordered nanostructures assembled from the monomeric unit are triggered by the weak noncovalent interactions consisting of hydrogen bonding, metal–ligand coordination, and π–π stacking.…”

Fluorescence-Selective Absorption and Circularly Polarized Fluorescence Energy Transfer Assist the Generation of Multicolor Circularly Polarized Luminescence in Chiral Helical Polyacetylene-Based Janus Nanofibers

“…Chiroptical nanomaterials with circularly polarized luminescence (CPL) performance are drawing substantial interest in multidisciplinary fields due to their promising potential in 3D displays, optical sensors, bioimaging, asymmetric catalysis, etc. − Among various CPL-active architectures, − CPL nanofibers have been widely studied, and most of them are prepared by a self-assembly strategy. − However, the nanofibers prepared by self-assembly are largely limited to specific systems, and the resulting products are discontinuous, which may not be conducive to practice applications. Delightedly, the past few years have witnessed the rapid development of an electrospinning technique, and it has proved to be an effective method for constructing flexible and continuous CPL nanofibers with a controlled morphology, uniformity, and the desired optical properties. − The advantages of electrospinning include ease of operation, reliable reproducibility, and low cost.…”