Fluorescence Turn-on Enantioselective Recognition of both Chiral Acidic Compounds and α‑Amino Acids by a Chiral Tetraphenylethylene Macrocycle Amine

New chiral tetraphenylethylene (TPE) macrocycles bearing optically pure amine groups were synthesized and found to have a discriminating ability between the two enantiomers of not only chiral acidic compounds but also α-amino acids by enantioselective aggregation and aggregation-induced emission (AIE) effects. NMR spectra, including 2D-NOESY, disclosed that the host–guest interaction of the macrocycle receptor played a key role in addition to the acid–base interactions

Density function study transition metal chromium-doped alkali clusters: the finding of magnetic superatom

<div><p>The structures, stabilities and magnetic properties of Cr<i>X_n</i> (<i>X</i> = Na, Rb and Cs; <i>n</i> up to 9) clusters are studied using density functional theory to search for the stable magnetic superatoms. The geometrical optimisations indicate the ground-state structures of Cr<i>X_n</i> evolve toward a close packed structure with an interior Cr atom surrounded by <i>X</i> atoms as the cluster size increase. Their stabilities are analysed by the relative energy, gain in energy (Δ<i>E</i>(<i>n</i>)) and the highest unoccupied molecular orbital and lowest unoccupied molecular orbital gaps. Furthermore, the magnetic moments of Cr<i>X_n</i> clusters show an odd–even oscillation. Here, we mainly focus on the Cr<i>X</i>₇ (<i>X</i> = Na, Rb and Cs) clusters due to the same valence count as the known stable magnetic superatoms VNa₈, VCs₈ and TiNa₉. Although these clusters all have a filled electronic configuration 1S²1P⁶ and large magnetic moment 5 μ_B, our studies indicate that only CrNa₇ is highly stable compared to its nearest neighbours, while CrRb₇ and CrCs₇ clusters are less stable. This suggests that Cr-doped Na₇ is most appropriate for filled electronic configuration and CrNa₇ is shown to be a stable magnetic superatom. More interesting, we find CrRb₈ and CrCs₈ with the filled electronic configuration 1S²1P⁶ have higher stability and large magnetic moment 6 μ_B in their respective series.</p></div

Monomer Emission and Aggregate Emission of an Imidazolium Macrocycle Based on Bridged Tetraphenylethylene and Their Quenching by C₆₀

A novel imidazolium macrocycle based on bridged tetraphenylethylene (TPE) was synthesized. Because it bears the bridged TPE units, this macrocycle not only displays an aggregation-induced emission (AIE) effect but also exhibits monomer emission, which is very rare in AIE compounds. With aggregation of the macrocycle, the aggregate emission increases while the monomer emission decreases. It was found that this imidazolium macrocycle can form a stable 2:1 complex with C₆₀, which gives rise to quenching of both the aggregate emission and the monomer emission. Unexpectedly, the aggregate emission exhibited a higher quenching efficiency than the monomer emission, probably because one adsorbed C₆₀ molecule could affect more macrocycle molecules in the aggregate

White-Light Emission of a Binary Light-Harvesting Platform Based on an Amphiphilic Organic Cage

White-light emissive materials with stable photophysical properties are of great importance for their potential applications in information display, fluorescent sensors, and optical-recording systems. Herein, an amphiphilic tetraphenylpyrazine (TPP)-based cage compound (TPP-Cage) was facilely synthesized by reaction of propeller-like TPP with aggregation-induced emission characteristics and triglycol monomethyl ether-substituted triazine. By immobilizing the twisted conformation of TPP, TPP-Cage showed obvious helical chirality in the solution and aggregated state. TPP-Cage emits strong deep blue fluorescence in solution due to the restriction of intramolecular rotation of the TPP unit. Its amphiphilic nature enables it to serve as an excellent light-harvesting platform to encapsulate diketopyrrolopyrrole (DPP) with aggregation-caused quenching effect in its hydrophobic cavity in aqueous medium, forming the DPP@TPP-Cage complex. Such inclusion prevents π–π stacking of DPP enabling it to emit strong yellow-light emission in the aggregated state. Due to the complementary emission colors of TPP-Cage and DPP, DPP@TPP-Cage exhibited stable white-light emission in the aggregated state and poly­(ethylene glycol) film. This work not only introduces a promising strategy for development of chiral compounds through immobilization of propeller-like achiral molecules but also provides a prospective pathway for white-light emission based on supramolecular assembly

The Fixed Propeller-Like Conformation of Tetraphenylethylene that Reveals Aggregation-Induced Emission Effect, Chiral Recognition, and Enhanced Chiroptical Property

The propeller-like conformation of tetraphenylethylene (TPE) with aggregation-induced emission (AIE) effect was partially and completely fixed by intramolecular cyclization for the first time. The immobilization of propeller-like conformation was found to show great advantages in determining the enantiomer purity, identifying the chiral amines. The completely fixed conformers are resolved into <i>M</i>- and <i>P</i>-enantiomer, which showed mirror imaged CD and almost quantitative fluorescence quantum yield. Furthermore, it also showed a mirror and large circularly polarized luminescence dissymmetric factor, depending on the helicity of the enantiomer. The result provides the most direct and persuasive evidence for AIE via the restriction of intramolecular rotation and finds the new insight of the compounds in chiroptical property

The Fixed Propeller-Like Conformation of Tetraphenylethylene that Reveals Aggregation-Induced Emission Effect, Chiral Recognition, and Enhanced Chiroptical Property

The propeller-like conformation of tetraphenylethylene (TPE) with aggregation-induced emission (AIE) effect was partially and completely fixed by intramolecular cyclization for the first time. The immobilization of propeller-like conformation was found to show great advantages in determining the enantiomer purity, identifying the chiral amines. The completely fixed conformers are resolved into <i>M</i>- and <i>P</i>-enantiomer, which showed mirror imaged CD and almost quantitative fluorescence quantum yield. Furthermore, it also showed a mirror and large circularly polarized luminescence dissymmetric factor, depending on the helicity of the enantiomer. The result provides the most direct and persuasive evidence for AIE via the restriction of intramolecular rotation and finds the new insight of the compounds in chiroptical property

The Fixed Propeller-Like Conformation of Tetraphenylethylene that Reveals Aggregation-Induced Emission Effect, Chiral Recognition, and Enhanced Chiroptical Property

The propeller-like conformation of tetraphenylethylene (TPE) with aggregation-induced emission (AIE) effect was partially and completely fixed by intramolecular cyclization for the first time. The immobilization of propeller-like conformation was found to show great advantages in determining the enantiomer purity, identifying the chiral amines. The completely fixed conformers are resolved into <i>M</i>- and <i>P</i>-enantiomer, which showed mirror imaged CD and almost quantitative fluorescence quantum yield. Furthermore, it also showed a mirror and large circularly polarized luminescence dissymmetric factor, depending on the helicity of the enantiomer. The result provides the most direct and persuasive evidence for AIE via the restriction of intramolecular rotation and finds the new insight of the compounds in chiroptical property

Monomer Emission and Aggregate Emission of TPE Derivatives in the Presence of γ‑Cyclodextrin

It was found for the first time that neutral amphiphilc tetraphenylethylene (TPE) derivatives showed an enhanced monomer emission and a decreased aggregate emission when they were included in the cavity of γ-cyclodextrin. This result provided a new insight into the aggregation-induced emission (AIE) effect

Enantioselective Recognition for Many Different Kinds of Chiral Guests by One Chiral Receptor Based on Tetraphenylethylene Cyclohexylbisurea

A neutral chiral receptor based on TPE cyclohexylbisurea was synthesized and could discriminate the enantiomers of many different kinds of chiral reagents, including chiral acidic compounds, basic compounds, amino acids, and even neutral alcohols. The ¹H NMR spectra disclosed that the ability of chiral recognition could be ascribed to the multiple hydrogen bonds and CH−π interactions between the TPE urea receptor and the enantiomer of the chiral guest, which led to the selective aggregation of the receptor with one of the two enantiomers. This result exhibited a great potential in enantiomer discernment and high-throughput analysis of enantiomer composition of these chiral analytes by one chiral AIE molecule