Chiroptical Helices of N‐Terminal Aryl Amino Acids through Orthogonal Noncovalent Interactions

Abstract

In the solid state, amino acids (alanine and phenylglycine) with appended pyrene segments self‐assembled into α‐helix‐like structures by asymmetrical H‐bonds between carboxylic acid and amide segments, further inducing supramolecular tilted chirality of the achiral pyrenes. These structures bind melamine and electron‐deficient units through H‐bond and charge‐transfer interactions, respectively. Charge‐transfer interactions enhance the dissymmetry g‐factor of absorption (gabs; up to 1.4×10−2) with an extended Cotton effect active region (from 250 to 600 nm). Incorporating melamine inverts the handedness of circularly polarized luminescence and boosts the dissymmetry g‐factor (glum). Melamine also induces macroscopic chirality at the nanoscale, whereby the 2D lamellar structures are transformed into 1D helices at the nanoscale, leading to giant tubular structures at the microscale.

Photoregulated “Breathing” Vesicle with Inversed Supramolecular Chirality

“…Actually, biomimetic studies on such a subject could be realized on the self-assembled liposome or vesicles which are readily fabricated by aqueous self-assembly of lipids or other amphiphiles. − Normal vesicles comprise cell membrane-like bilayer structures enclosing a cavity full of water. , Compared to the 1D aggregates, vesicle membranes are loosely constituted, allowing for the “flip-flop” of building units and dynamic exchange with free amphiphiles in bulky water . As a consequence, chirality transfer from molecular chirality to supramolecular scale is rather challenging, and relevant studies have rarely been reported to date. − Unlike the supramolecular chiral structures such as helical fibers, screw particles, or tubes, vesicles are not favorable aggregates to show chirality at the nanoscale. , Thus, the evaluation of supramolecular chirality may dominantly rely on their chiroptical properties. − Cotton effect is a key feature of self-assemblies with supramolecular chirality, which reflects the asymmetrical packing of chromophores on the basis of exciton chirality rule built by Harada and Nakanishi. − …”