Analytical Chemistry
DOI: 10.1021/acs.analchem.3c02165
Calix[4]arene‐based Supramolecular Gels for Mercury Ions Removal in Water
A calix[4]arene-based gelator 1, with lower-rim mono triazolylpyridine group, capable of spontaneous self-assembly into microspheres in different ethanol/H2O mixtures, is synthesized. The concentration-dependent 1H NMR spectra and X-ray single crystal structure of 1 provided evidences for self-assembly of gelator 1 via cooperative interactions of intermolecular noncovalent forces. Furthermore, metallogels by self-assembly of 1 was found to exhibit remarkable selectivity toward Hg2+ ions. 1H NMR spectra support that Hg2+ ion was bound to the nitrogen atoms of two coordination sites of 1, which composed of triazole and pyridine. Moreover, the results of Field Emission Scanning Electron Microscopy and rheology experiments indicated that Hg2+ ions not only enhanced the gelling ability of gelator 1 in ethanol but also led to morphological change of its self-assembly through metal-ligand interactions. Finally, the in situ gelation, triggered by mixing a gelator solution of 1 in ethanol with water samples (DI, tap and lake water), leads to the effective removal of Hg(II) from a water sample which reduced from 400 to 1.6 ppm.
[ASAP] Rb2Sn4Q9 (Q = S and Se): Low-Dimensional Noncentrosymmetric Chalcogenides with High Laser-Induced Damage Threshold
Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c01962
Stabilizing Pseudouridimycin: Synthesis, RNA Polymerase Inhibitory Activity, and Antibacterial Activity of Dipeptide‐Modified Analogues
Strategic modification of the guanidine tail and central hydroxamate bond in the antibacterial natural product pseudouridimycin (PUM) dramatically enhances its chemical stability. Three hydroxamate-modified analogues retain much of the antibacterial activity of PUM despite reduced RNAP-inhibitory activity. Stabilization of the hydroxamate C−N bond in PUM represents a viable strategy toward clinically relevant analogues.
Abstract
Pseudouridimycin (PUM) is a microbially produced C-nucleoside dipeptide that selectively targets the nucleotide addition site of bacterial RNA polymerase (RNAP) and that has a lower rate of spontaneous resistance emergence relative to current drugs that target RNAP. Despite its promising biological profile, PUM undergoes relatively rapid decomposition in buffered aqueous solutions. Here, we describe the synthesis, RNAP-inhibitory activity, and antibacterial activity of chemically stabilized analogues of PUM. These analogues feature targeted modifications that mitigate guanidine-mediated hydroxamate bond scission. A subset of analogues in which the central hydroxamate is replaced with amide or hydrazide isosteres retain the antibacterial activity of the natural product.
Selective Excitation of Pd‐decorated Titania Enables Consecutive C−C Couplings and Hydrogenations under Ambient Conditions
Pd-decorated titania is a versatile heterogeneous photocatalyst capable of driving consecutive reactions by adjusting excitation conditions. Poisoning species generated in the first reaction step can be easily separated by alumina plugs, allowing only the alkyne product to reach the second reaction step and to undergo through the transfer hydrogenation path.
Abstract
Here, we discovered that Pd decorated TiO2 (Pd@TiO2) enables consecutive photocatalytic Sonogashira C−C coupling and hydrogenation steps by simply adjusting the excitation conditions of the reaction. We demonstrated that by-products containing iodine species generated in the first reaction step can inhibit subsequent photocatalytic processes, but they can be easily removed from solution to enable a compatible synthetic sequence for new C−C bond formation under mild reaction conditions. This work incorporates heterogeneous photocatalysts into consecutive transformations, promoting elegant reactions while meeting the demands of green chemistry.
Diphenylpyrrole‐Strapped Calix[4]pyrrole Extractant for the Fluoride and Chloride Anions
![Diphenylpyrrole-Strapped Calix[4]pyrrole Extractant for the Fluoride and Chloride Anions](https://onlinelibrary.wiley.com/cms/asset/4bcfa8dc-25ef-403f-b5f3-39ad7f130461/chem202302410-toc-0001-m.png)
Extractants: The diphenylpyrrole-strapped calix[4]pyrrole and its dual host systems involving crown ethers enable the extraction of various fluoride and chloride salts from water.
Abstract
The anion binding features of diphenylpyrrole-strapped calix[4]pyrrole 1 have been investigated by means of 1H NMR spectroscopy and ITC (isothermal titration calorimetry), as well as single crystal X-ray diffraction analyses. Receptor 1 bearing an auxiliary pyrrolic NH donor and solubilizing phenyl groups on the strap was found to bind F−, Cl−, and Br− as their tetrabutylammonium salts with high affinity in DMSO-d6 . In addition, receptor 1 was found to extract the fluoride anion (as both its tetraethylammonium (TEA+) and tetrabutylammonium (TBA+) salts), as well as the chloride anion into chloroform-d from an aqueous source phase. Cation metathesis using TBAI or the use of a dual host approach involving crown ethers enabled receptor 1 to extract simple alkali metal fluoride or chloride salts from water. Quantitative binding of NaF by receptor 1 was observed in 20 % D2O-DMSO-d6 allowing for the direct determination of the NaF concentration in an unknown sample.
Facile Fabrication of Dual‐Activatable Gastrointestinal‐Based Nanocarriers for Safe Delivery and Controlled Release of Methotrexate
An oral gastrointestinal-based anticancer nanocarrier (Am7CD/SDS NPs) was equipped with both pH and temperature sensitivity, which could effectively prevent MTX@Am7CD/SDS NPs from being degraded in the acidic environment mimicking the stomach and small intestine, thus harboring the potential to accumulate at the site of colon lesions and further release drugs under mild conditions.
Abstract
Colon cancer is emerging as one of the most common cancers worldwide, ranking in the top three in morbidity and mortality. Oral methotrexate (MTX) has been employed as a first-line treatment for various cancers, such as colon, breast, and lung cancer. However, the complexity and particularity of the gastrointestinal microenvironment and the limitations of MTX itself, including severe adverse effects and instability, are the main obstacles to the safe delivery of MTX to colon tumor sites. Herein, an innovative oral administrated anticancer therapeutic MTX@Am7CD/SDS NPs equipped with both pH and temperature sensitivity, which could effectively prevent MTX@Am7CD/SDS NPs from being degraded in the acidic environment mimicking the stomach and small intestine, thus harboring the potential to accumulate at the site of colon lesions and further release intestinal drug under mild conditions. In cellular assays, compared with free MTX, MTX@Am7CD/SDS NPs showed a favorable tumor inhibition effect on three tumor cell lines, as well as excellent cell uptake and apoptosis-inducing effect on SW480 cells. Therefore, this work provides a feasible solution for the safe use of MTX in the treatment of colon cancer and even other intestinal diseases.
From Natural Insulin to Designed Analogs: A Chemical Biology Exploration
Insulin has been at the forefront of scientific breakthroughs in the past century. In this article, we highlight the pivotal role of chemical biology in driving these innovations and discuss how it continues to shape the future trajectory of insulin research.
Abstract
Since its discovery in 1921, insulin has been at the forefront of scientific breakthroughs. From its amino acid sequencing to the revelation of its three-dimensional structure, the progress in insulin research has spurred significant therapeutic breakthroughs. In recent years, protein engineering has introduced innovative chemical and enzymatic methods for insulin modification, fostering the development of therapeutics with tailored pharmacological profiles. Alongside these advances, the quest for self-regulated, glucose-responsive insulin remains a holy grail in the field. In this article, we highlight the pivotal role of chemical biology in driving these innovations and discuss how it continues to shape the future trajectory of insulin research.
Towards the Operational Window for Nitridic and Carbidic Palladium Nanoparticles for Directed Catalysis
Three interstitial structures of palladium which can form under reactive conditions, PdNx, PdCx, and PdHx, have been characterised using in situ X-ray absorption spectroscopy. The thermal stability of the carbide and nitride under both inert and reducing conditions were assessed. Solid-state NMR and DFT measurements were performed for palladium nitride to further unravel its structure and stability.
Abstract
The reactions under which interstitial structures of Pd form are profoundly important and prevalent in catalysis; the formation and stability of Pd hydride structures are well understood, however, interstitial structures of the carbide and nitride are relatively under explored. This work reports a systematic study of the formation and stability of PdCx and PdNx at elevated temperatures and different atmospheres using in situ Pd L3 edge XANES spectroscopy. These studies were further complemented by the application of 14N MAS-NMR experiments and computational DFT investigations. The experiments confirmed that PdCx was significantly more stable than PdNx; 14N MAS-NMR provided direct confirmation on the formation of the nitride, however, the XANES studies evidenced very limited stability under the conditions employed. Moreover, the results suggest that the formation of the nitride imparts some structural changes that are not entirely reversible under the conditions used in these experiments. This work provides important insights into the stability of interstitial structures of Pd and the conditions in which they could be employed for directed catalytic processes.
2D Non‐van der Waals Nanoplatelets of Hematene and Magnetene: Nonlinear Optical Response and Optical Limiting Performance from UV to NIR
The present study reports that non-van der Waals 2D materials, hematene and magnetene, show very efficient optical limiting (OL) from UV to visible, with their optical limiting onset (OLon) values exhibiting a decreasing trend towards UV irradiation wavelengths. The obtained results render these materials very promising candidates for OL-related applications, such as the protection of human retinal from high-power laser.
Abstract
Recently, the preparation of some hematene and magnetene ultrathin non van der Waals (non-vdW) 2D nanoplatelets was reported starting from hematite and magnetite natural iron ores. The present work reports on the determination and evaluation of the nonlinear optical response and the optical limiting (OL) action of these 2D nanoplatelets dispersed in water under ns laser excitation. The obtained results show that both hematene and magnetene exhibit strong nonlinear absorption and refraction, comparable and even larger than those of other van der Waals (vdW) 2D counterpart materials. In addition, due to their strong nonlinear absorption, both hematene and magnetene show exceptional OL performance from the UV to visible, attaining very low values of optical limiting onset (OLon), comparable and even lower than that of vdW 2D nanomaterials, such as graphene, graphene oxide, other transition metal dichalcogenides like MoS2, WS2 and MoSe2, black phosphorous and antimonene. Moreover, hematene was found to exhibit more efficient OL action than magnetene for all the excitation wavelengths studied, attributed to more efficient ligand to metal charge transfer. The present findings open new possibilities for the potential use of these non-vdW 2D materials in photonics and optoelectronics, e. g., as optical limiters and optical switchers.