Chirality control of self-assembled achiral nanofibers using amines in their solid state

Abstract

Although there are numerous examples of helical and spiral conformations in nature, including plant tendrils, snail shells, and even collagen, the occurrence of supramolecular systems that are able to reversibly undergo solid-to-solid helical transformation based on environmental chiral triggers is rare. In this work, we present a supramolecular, non-helical nanofiber which shows a distinct helical rearrangement in the presence of specific diamines and monoamines, such as cyclohexanediamines, alanine, lysine, and phenylalanine, depending on the molecular chirality of the surrounding analytes. A detailed investigation on the structural organization of the nanofibers using SEM and CD spectra analysis confirmed the repeatable and reversible nature of this amplification of chiral information. Further preparation of an electrospun nanofiber film was demonstrated for distinguishing chiral diamines and monoamines in solution by film immersion and CD analysis, which is the first example of amplification of chiral information in the solid-state using electrospun nanofiber films. With this system, we could demonstrate a reusable means for detecting the molecular chirality, which also provided a unique example of reversible control of solid state rearrangement in supramolecular helicity.

Mechanically Controlled and Consecutively Boosted Circularly Polarized Luminescence of Nanoassemblies from Achiral Molecules

“…Diaminocyclohexane (DAC) is usually used as chiral additive to control the supramolecular chirality of achiral molecular assemblies. 58,59 As shown in Figure S18, CPL signs of BTABA assemblies were controlled by adding an equivalent of DAC. Samples with Ror S-type DAC displayed a negative or a positive CPL, respectively.…”

“…We also compared the seeds-involved VAA method and the commonly used strategy based on “sergeant–soldier rule” with chiral molecules to control the chirality after symmetry breaking. Diaminocyclohexane (DAC) is usually used as chiral additive to control the supramolecular chirality of achiral molecular assemblies. , As shown in Figure S18, CPL signs of BTABA assemblies were controlled by adding an equivalent of DAC. Samples with R - or S -type DAC displayed a negative or a positive CPL, respectively.…”

Enantioselective Recognition by Chiral Supramolecular Gels

“…Jung et al. described gelator nanofibers formed by an achiral disc‐like azobenzoic acid that exhibited enantioselectivity to chiral amines . The CD spectra of the nanofibrous gels in the presence of asymmetric diamine ((1 R ,2 R )‐ and (1 S ,2 S )‐DACH) were observed to determine the chiroptical response.…”

“…Jung et al described gelator nanofibers formed by an achiral disc-likea zobenzoic acid that exhibited enantioselectivity to chiral amines. [56] The CD spectra of the nanofibrous gels in the presence of asymmetric diamine ((1R,2R)-and (1S,2S)-DACH) were observed to determine the chiroptical response. In the case of (1R,2R)-DACH, an egative CD signalw as obtained for the first Cotton effect at l = 432 nm, which confirmed the lefthandedh elical orientation and was consistent with SEM images.…”

Helical Mesoporous Tantalum Oxide Nanotubes: Formation, Optical Activity, and Applications

“…With the development of supramolecular chemistry, it has been found that low‐molecular‐weight compounds can self‐assemble into a variety of helical nanostructures through non‐covalent interactions. The handedness of the self‐assemblies is controlled by the chirality of the compounds and the surrounding conditions . Nanomaterials can also be shaped into helical structures.…”