Adaptive Chirality of an Achiral Cucurbit[8]uril‐Based Supramolecular Organic Framework for Chirality Induction in Water

Abstract

Chiral framework materials have been developed for many applications including chiral recognition, chiral separation, asymmetric catalysis, and chiroptical materials. Herein, we report that an achiral cucurbit[8]uril‐based supramolecular organic framework (SOF‐1) with the dynamic rotational conformation of tetraphenylethene units can exhibit adaptive chirality to produce M‐SOF‐1 or P‐SOF‐1 with mirror‐image circular dichroism (CD) with gabs≈±10−4 and circularly polarized luminescence (CPL) with glum≈±10−4 induced by L‐/D‐phenylalanine in water, respectively. The chirality induction in CD (gabs≈−10−4) and CPL (glum≈−10−4) of P‐SOF‐1 from achiral SOF‐1 can be presented by using a small amount of adenosine‐5′‐triphosphate disodium (ATP) or adenosine‐5′‐diphosphate disodium (ADP) (only 0.4 equiv) in water. Furthermore, the adaptive chirality of SOF‐1 can be used to determine dipeptide sequences (e.g., Phe‐Ala and Ala‐Phe) and distinguish polypeptides/proteins (e.g., somatostatin and human insulin) with characteristic CD spectra. Therefore, achiral SOF‐1 as an ideal chiroptical platform with adaptive chirality may be applied to determine the enantiopurity of amino acids (e.g., L‐/D‐phenylalanine), develop aqueous CPL materials, and distinguish biological chiral macromolecules (e.g., peptides/proteins) via chirality induction in water.

Adaptive Chirality of an Achiral Cucurbit[8]uril‐Based Supramolecular Organic Framework for Chirality Induction in Water

“…Based on previous reports, M-TPE and P-TPE show positive and negative Cotton effects from long to short wavelengths, respectively. [22,24] Therefore, in these cases, L-Phe induces an M rotational conformation of the TPE units in the SOF to produce M-SOF-1, while D-Phe induces a P rotational conformation of the TPE units in the SOF to produce P-SOF-1 (Scheme 1 b and Figure 3 d). The mirror-image CD spectra confirmed that the adaptive chirality of SOF-1 with a P or M rotational conformation of the TPE units can be induced by enantiomers when the enantiomers are encapsulated inside the cavities/pores of SOF-1, respectively.…”

“…The X-ray structure of 1 exhibits a propeller-like conformation with racemic P-and M-rotation of the TPE units in the crystalline state (Figure 3 a and Table S4). [24] As expected, 1 did not exhibit any obvious Cotton effect at different concentrations (1.0 mM-1.0 mM) and temperatures (283-333 K) in water and in different solvent systems (e.g., acetone, dioxane, EtOH, MeCN, MeOH, and THF), respectively, indicating that the TPE units in free 1 adopt racemic rotational conformation in the solution state and their homodirectional rotational (P or M) conformation cannot be easily induced and stabilized in the aggregation state or under low temperature ( Figures S27-S29). Similarly, SOF-1 did not show any obvious Cotton effect under different conditions in water or other solvents, indicating that the TPE units in the framework also adopt a racemic rotational conformation in the solution state, and their homodirectional rotational conformation (P or M only) cannot be easily induced and stabilized in the supramolecular assembly ( Figures S27-S29).…”

Two Unexpected Temperature-Induced Supermolecular Isomers from Multi-Topic Carboxylic Acid: Hydrogen Bonding Layer or Helix Tube

“…Analysis of the crystal structure suggests that 1-H is a chiral supramolecular organic framework [32], which entails the self-assembly of homo-chiral (right-helix) tubes derived from the achiral semi-rigid tetra-acids being assembled via different hydrogen bond motifs. It has been confirmed in a kinetic model that an achiral artificial assembly system could spontaneously produce chirality [33].…”

Surface chiroselective assembly of enantiopure crystalline porous films containing bichiral building blocks

“…The development of chiral materials has attracted great attention to their potential applications in the pharmaceutical, 1 agricultural, 2 chemical and biological elds. [3][4][5][6] As emerging chiral materials, chiral crystalline porous materials (CPMs) including metal-organic frameworks (MOFs), [7][8][9][10] covalentorganic frameworks (COFs) [11][12][13] and supramolecular-organic frameworks (SOFs) [14][15][16] possess high specic surface area, well-dened pores and variable chemical functionalities. Chiral CPMs have been rapidly expanded in enantiomer separation, [17][18][19][20][21][22] asymmetric catalysis, [23][24][25][26] nonlinear optics, 27 circularly polarized luminescence (CPL), 28,29 drug delivery 30,31 and chiral sensing.…”