An Ir‐catalyzed asymmetric hydrogenation of α‐imino esters with unsymmetrical hybrid chiral ferrocenylphosphine‐phosphoramidite ligands for the synthesis of optically active α‐aryl glycines has been ...described. The result indicated that the presence of the iodo‐substitutent at the 3/3’‐position of the binaphthyl unit of ligand could significantly improve the catalytic performance. This method features high asymmetric induction and reasonable functional group tolerance, thus providing a concise and efficient approach toward chiral α‐aryl glycine derivatives with up to 96% ee.
Calixarenes (CAs), representing the third generation of supramolecular hosts and one of the most widely studied macrocyclic scaffolds, offer (almost) unlimited structure and application possibilities ...due to their ease of modification, which allows one to establish a large molecular library as a material basis for diverse biomedical applications. Moreover, CAs and their derivatives engage in various noncovalent interactions for the facile recognition of guests including bioactive molecules and are also important building blocks for the fabrication of supramolecular architectures. In view of their molecular recognition and self‐assembly properties, CAs are extensively applied in biosensing, bioimaging, and drug/gene delivery. Additionally, some CA derivatives exhibit biological activities and can therefore be used as new therapeutic agents. Herein, we summarize the diverse biomedical applications of CAs including in vitro diagnosis (biosensing), in vivo diagnosis (bioimaging), and therapy.
Calixarenes (CAs) represent the third generation of supramolecular hosts and one of the most widely studied macrocyclic scaffolds. They offer almost unlimited structural possibilities due to their ease of modification, providing a tremendous molecular library as a material basis for diverse biomedical applications.
Enhanced drug delivery can improve the therapeutic efficacy of drugs and help overcome side effects. However, many reported drug‐delivery systems are too complex and irreproducible for practical use. ...In this work, the design of a hypoxia‐responsive molecular container based on calixarene, called CAC4A, which presents a significant advance in practical, hypoxia‐targeted drug‐delivery, is reported. CAC4A enables a wide variety of clinical drugs to be quantitatively loaded to improve their solubility and stability, as well as enable the administration of reduced doses. Furthermore, as a result of its azo functional groups, which are sensitive to reduction within a hypoxic environment, it is possible to achieve tumor‐targeted drug‐release with reduced side effects. CAC4A fulfils all essential requirements for a drug‐delivery system in addition to multiple advantages, including facile preparation, well‐defined molecular weight, and structure, and universal applicability. Such features collectively enable supramolecular prodrugs to be formulated simply and reproducibly, with potential for bench‐to‐bedside translation. Moreover, CAC4A is amenable to other therapy modalities and can be facilely decorated with functional groups and hybridized with nanomaterials, providing ample possibilities for its role in future drug‐delivery systems.
Carboxylated azocalix4arene is designed as a hypoxia‐responsive molecular container, which affords strong binding toward a series of chemotherapeutic drugs, and improves the drugs’ solubility and stability, demonstrating its universality as a supramolecular drug carrier. Taking one supramolecular prodrug as an example, the efficacy of this hypoxia‐targeted therapy is validated in vitro and in vivo.
In a comparative study of the electrocatalytic CO2 reduction, cobalt meso‐tetraphenylporphyrin (CoTPP) is used as a model molecular catalyst under both homogeneous and heterogeneous conditions. In ...the former case, employing N,N‐dimethylformamide as solvent, CoTPP performs poorly as an electrocatalyst giving low product selectivity in a slow reaction at a high overpotential. However, upon straightforward immobilization of CoTPP onto carbon nanotubes, a remarkable enhancement of the electrocatalytic abilities is seen with CO2 becoming selectively reduced to CO (>90 %) at a low overpotential in aqueous medium. This effect is ascribed to the particular environment created by the aqueous medium at the catalytic site of the immobilized catalyst that facilitates the adsorption and further reaction of CO2. This work highlights the significance of assessing an immobilized molecular catalyst from more than homogeneous measurements alone.
Heterogeneous vs. homogeneous: When cobalt meso‐tetraphenylporphyrin (CoTPP) is immobilized on carbon nanotubes, a remarkably enhanced catalytic activity in CO2 electroreduction is observed, with CoITPP− serving as the active species. The simple approach for heterogenization enables facile screening and evaluation of molecular catalysts under heterogeneous conditions.
A nitrogen‐stabilized single‐atom catalyst containing low‐valence zinc atoms (Znδ+‐NC) is reported. It contains saturated four‐coordinate (Zn‐N4) and unsaturated three‐coordinate (Zn‐N3) sites. The ...latter makes Zn a low‐valence state, as deduced from X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory. Znδ+‐NC catalyzes electrochemical reduction of CO2 to CO with near‐unity selectivity in water at an overpotential as low as 310 mV. A current density up to 1 A cm−2 can be achieved together with high CO selectivity of >95 % using Znδ+‐NC in a flow cell. Calculations suggest that the unsaturated Zn‐N3 could dramatically reduce the energy barrier by stabilizing the COOH* intermediate owing to the electron‐rich environment of Zn. This work sheds light on the relationship among coordination number, valence state, and catalytic performance and achieves high current densities relevant for industrial applications.
A nitrogen‐anchored low‐valence Zn single‐atom catalyst, containing coordinately unsaturated Zn‐N3 active sites, can boost electrochemical CO2 reduction to industrial application levels.
The realization of optical non-reciprocity is crucial for many applications, and also of fundamental importance for manipulating and protecting the photons with desired time-reversal symmetry. ...Recently, various new mechanisms of magnetic-free non-reciprocity have been proposed and implemented, avoiding the limitation of the strong magnetic field imposed by the Faraday effect. However, due to the difficulties in separating the signal photons from the drive laser and the noise photons induced by the drive laser, these devices exhibit limited isolation performances and their quantum noise properties are rarely studied. Here, we demonstrate an approach of magnetic-free non-reciprocity by optically-induced magnetization in an atom ensemble. Excellent isolation (highest isolation ratio is Formula: see text) is observed over a power dynamic range of 7 orders of magnitude, with the noiseless property verified by quantum statistics measurements. The approach is applicable to other atoms and atom-like emitters, paving the way for future studies of integrated photonic non-reciprocal devices.
Two-dimensional crystals are emerging materials for nanoelectronics. Development of the field requires candidate systems with both a high carrier mobility and, in contrast to graphene, a sufficiently ...large electronic bandgap. Here we present a detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) to predict its electrical and optical properties. This system has a direct bandgap, tunable from 1.51 eV for a monolayer to 0.59 eV for a five-layer sample. We predict that the mobilities are hole-dominated, rather high and highly anisotropic. The monolayer is exceptional in having an extremely high hole mobility (of order 10,000 cm(2) V(-1) s(-1)) and anomalous elastic properties which reverse the anisotropy. Light absorption spectra indicate linear dichroism between perpendicular in-plane directions, which allows optical determination of the crystalline orientation and optical activation of the anisotropic transport properties. These results make few-layer BP a promising candidate for future electronics.
A highly diastereo- and enantioselective Ir-catalyzed hydrogenation of unfunctionalized 2,3-disubstituted quinolines, especially 3-alkyl-2-arylquinolines, has been realized. The success of this ...hydrogenation is ascribed to the use of a structurally fine-tuned chiral phosphine–phosphoramidite ligand with a (S a )-3,3′-dimethyl H8-naphthyl moiety and (R c )-1-phenylethylamine backbone. The hydrogenation displayed broad functional group tolerance, thus furnishing a wide range of optically active 2,3-disubstituted tetrahydroquinolines in up to 96% ee and with perfect cis-diastereoselectivity.
Nineteen new quinoline derivatives were prepared via the Mannich reaction and evaluated for their antibacterial activities against both Gram-positive (G⁺) and Gram-negative (G
) bacteria, taking ...compound
as the lead. Among the target compounds, quinolone coupled hybrid
exerted the potential effect against most of the tested G⁺ and G
strains with MIC values of 0.125⁻8 μg/mL, much better than those of
. Molecular-docking assay showed that compound
might target both bacterial LptA and Top IV proteins, thereby displaying a broad-spectrum antibacterial effect. This hybridization strategy was an efficient way to promote the antibacterial activity of this kind, and compound
was selected for the further investigation, with an advantage of a dual-target mechanism of action.
Recently, a large number of nanostructured metal‐containing materials have been developed for the electrochemical CO2 reduction reaction (eCO2RR). However, it remains a challenge to achieve high ...activity and selectivity with respect to the metal load due to the limited concentration of surface metal atoms. Here, it is reported that the bismuth‐based metal–organic framework Bi(1,3,5‐tris(4‐carboxyphenyl)benzene), herein denoted Bi(btb), works as a precatalyst and undergoes a structural rearrangement at reducing potentials to form highly active and selective catalytic Bi‐based nanoparticles dispersed in a porous organic matrix. The structural change is investigated by electron microscopy, X‐ray diffraction, total scattering, and spectroscopic techniques. Due to the periodic arrangement of Bi cations in highly porous Bi(btb), the in situ formed Bi nanoparticles are well‐dispersed and hence highly exposed for surface catalytic reactions. As a result, high selectivity over a broad potential range in the eCO2RR toward formate production with a Faradaic efficiency up to 95(3)% is achieved. Moreover, a large current density with respect to the Bi load, i.e., a mass activity, up to 261(13) A g−1 is achieved, thereby outperforming most other nanostructured Bi materials.
A bismuth‐containing metal–organic framework transforms to an ensemble of bismuth nanoparticles dispersed in a porous organic matrix under electrochemical conditions in aqueous solution. When used as a catalyst in the electroreduction of carbon dioxide, it selectively produces formate (≈95%) with large activity relative to the metal content (≈261 A g−1), outperforming previously reported bismuth‐based materials.
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