Inversion of Supramolecular Chirality by In Situ Hydrolyzation of Achiral Diethylene Glycol Motifs

Abstract

Chiral inversion of supramolecular assemblies is of great research interest due to its broad practical applications. However, chiral structure transition induced by in situ regulation of building molecules has remained a challenge. Herein, left-handed fibrous assemblies were constructed by C 2-symmetic l -phenylalanine coupled with diethylene glycol (LPFEG) molecules. In situ hydrolyzing terminal diethylene glycol motifs in LPFEG successfully inverted the chirality of the nanofibers from left- to right-handedness. The transition of right-handed fibers into left-handed fibers could also be achieved via hydrolyzing DPFEG molecules. Circular dichroism (CD) spectroscopy, 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy revealed that the back-folded achiral diethylene glycol played a vital role in L/DPFEG molecular arrangements and removing terminal diethylene glycol could induce the opposite rotation of molecular assemblies. Thanks to this merit, the enantioselective separation of racemic phenylalanine was obtained and the enantiomeric excess (ee) values could achieve around ±20% after separation. This study not only provides a new strategy to regulate the chiral structure via dynamic modulation of terminal substituents but also presents a promising application in the field of enantioselective separation.

Ternary Assemblies of TADF Core/TDBC-J-Aggregate Shell Nanoparticles and d/l-Phenylalanine-Based Nanohelixes for Circularly Polarized Luminescence

“…The nanohelixes in d - and l -PFEG hydrogels exhibit right- (P-type) and left-handed (M-type) helical structures, respectively. The diameters of d - and l -PFEG nanohelixes were estimated to be 100–150 nm with a 400–800 nm helical pitch without any significant difference between P- and M-type nanohelixes, which is consistent with the previous report …”

“…In H 2 O/EtOH (v/v = 5/1) solution, the dissolving temperature of d / l -PFEG monomers decreases to 70 °C, which is compatible with TDBC aggregation. By slowly cooling down to room temperature, the self-assembled d / l -PFEG hydrogels were formed (Figure a), which exhibit a slightly red-shifted absorption peak from ∼242 (in EtOH solution) to ∼247 (in H 2 O/EtOH hydrogel) nm (Figure b), indicating the supramolecular self-assembly of d / l -PFEG . The CD spectra of d - and l -PFEG hydrogels exhibit evident Cotton effect-induced mirrored peaks splitting in the deep UV regime (Figure c), − which indicates that d - and l -PFEG monomers were assembled into chiral nanohelixes with opposite handed directions.…”

“…By slowly cooling down to room temperature, the self-assembled D/L-PFEG hydrogels were formed (Figure 3a), which exhibit a slightly red-shifted absorption peak from ∼242 (in EtOH solution) to ∼247 (in H 2 O/EtOH hydrogel) nm (Figure 3b), indicating the supramolecular self-assembly of D/L-PFEG. 65 The CD spectra of D-and L-PFEG hydrogels exhibit evident Cotton effect-induced mirrored peaks splitting in the deep UV regime (Figure 3c), 66−68 which indicates that D-and L-PFEG monomers were assembled into chiral nanohelixes with opposite handed directions. The SEM images of spin-coated D-and L-PFEG hydrogels on silicon substrates are displayed in Figure 3d,e, respectively.…”

“…The diameters of D-and L-PFEG nanohelixes were estimated to be 100−150 nm with a 400−800 nm helical pitch without any significant difference between P-and M-type nanohelixes, which is consistent with the previous report. 65 The ternary hydrogels including TADF-NPs, TDBC, and D/ L-PFEG were further prepared by co-assembling in a H 2 O/ EtOH system at 70 °C, while binary hydrogels (TADF-NPs and D/L-PFEG) were prepared with identical conditions as a comparison. Optical (bright field and fluorescence) wide-field microscopy was employed to characterize the attachment of nanoparticles on nanohelixes, which is critical for chiral transfer.…”

A chiral microenvironment promotes retinal progenitor cell proliferation by activating the Akt and ERK pathways

“…S1b †). 19 Non-helical fibers (RP fibers) were obtained from racemic mixtures (RP molecules) of LP and DP molecules (molar ratio of LP and DP was 1 : 1). Circular dichroism (CD) measurements were performed to further investigate the chiroptical activities of the self-assembled fibers (Fig.…”