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.

Stabilization and Multiple-Responsive Recognition of Natural Base Pairs in Water by a Cationic Cage

“…Similarly, CD spectra of 1 (20 μM) with a 1:1 mixture of G and C also exhibited two new negative CD signals centered at 330 nm (g abs ≈ −2.7 × 10 −4 ) and 395 nm (g abs ≈ -2.8 × 10 −4 ), and stronger negative/positive CD signals at 200-250 nm (g abs(220 nm) ≈ −4.40 × 10 −4 ) and 250-300 nm (g abs (280 nm) ≈ 1.8 × 10 −4 ) when compared with free guests (Figure 4b and Supporting Information Table S4). Based on previous reports [18][19][20]31,33,34 and theoretical calculations (Supporting Information Figure S18), the negative Cotton effect in the 300-450 nm region is attributed to the P-rotational conformation of TPE units, strongly suggesting that P-rotational conformation of TPE units on the chiral host-guest complexes is preferential. Energyminimized structures of possible chiral host-guest complexes show that the dynamic conformation transformation from MP-1/MM-1 to PP-1 is an energy-favored process when a cage binds with base pairs (Supporting Information Figure S19).…”

“…The correlation between CD and CPL signals reveals that the chiral host-guest complexes with negative Cotton effect in the 300-450 nm region display negative CPL. [18][19][20]33,34 Therefore, P-rotational conformation of TPE units in the cage has a definite chirality relationship between the negative Cotton effect in the 300-450 nm region and the negative CPL centered at 550 nm.…”

“…[12][13][14][15] The water-soluble tetraphenylethene (TPE)-based octacationic cage (1) possesses remarkable absorption, excellent fluorescence, and adaptive chirality (Scheme 1a, top). [16][17][18][19][20] Based on the left-handed (M) and right-handed (P) rotational conformation of two TPE units (Scheme 1a, bottom), in theory, 1 can have three conformational isomers. including mesomeric PM-1 and a pair of racemic MM-1 and PP-1.…”

Supramolecular Nanohelix Fabricated by Pillararene-Based Host–Guest System for Chirality Amplification, Transfer, and Circularly Polarized Luminescence in Water

“…[27][28][29] The resulting supramolecular self-assembled chiral materials were responsive to circularly polarized light and could produce active CPLsignals with higher luminescence dissymmetry factor (g lum ) in an aqueous medium than that of normal systems in organic solvents or binary solvent mixtures (g lum = 10 -5 to 10 -3 ). [30][31][32][33][34] In order to extend the application of CPL-active materials, a high g lum value of the resulting chiral luminescent materials is an important prerequisite. Therefore, the hierarchical supramolecular self-assembly approach has played an active role in improving the CPL activity.…”

Efficient Photoinduced Energy and Electron Transfers in a Tetraphenylethene-Based Octacationic Cage Through Host–Guest Complexation

“…On the other hand, pyridinium ring with electron-deficient property could be an efficient electron-transfer acceptor . Recently, we combined these two molecular building blocks to construct a series of supramolecular hosts including macrocycles, cages, and frameworks, which exhibited promising applications in host–guest recognitions, light-harvesting systems, and stimuli-responsive fluorescent materials. − Specially, combined with the TPE unit and pyridinium ring, the tetraphenylethene-based octacationic cage ( 1· 8X) has excellent fluorescence property and host–guest recognition ability for electron-rich polycyclic aromatic hydrocarbons via CH-π and π–π interactions in both the solution and the crystalline states. As a result, this cage is endowed with several features which make it well suited for studying PEnT and PET processes when forming host–guest complexes with dye guests (Figure a).…”