Latest ArticlesPalladium-catalyzed cycloaddition reactions via Pd-π-allyl zwitterions have been established as significant synthetic transformations to enable numerous carbon- or heterocycles compounds that are key constituents of various biologically active natural products and pharmaceuticals. In addition to the well-known Pd-π-allyl zwitterions,including palladium-trimethylenemethane and Pd-1,3/1,4-zwitterions,chemists have recently discovered new applications of several long ago reported but less-studied Pd-π-allyl zwitterions,which can straightforwardly and efficiently construct novel cyclic architectures. Meanwhile,some impressive newly designed zwitterions have been also developed. Those zwitterions are diverse and can serve as transient and highly reactive intermediates for the subsequent cyclization with various acceptors. In this review,we highlight recent advances in applications of these two types of zwitterions in the synthesis of complex polycyclics and medium-sized cyclic compounds.
Identification of lymph nodes (LNs) is critical for studies of the structure, the role in disease development, and the efficacy of disease treatment. Carbonized polymer dots (CPDs) are expected to be potential LNs-targeted imaging agents due to their excellent properties with special structure, better photoluminescence (PL) and great biocompatibility. Herein, a red/near infrared (NIR) emission CPDs (RCPDs) with one and two-photon bioimaging based on citric acid (CA) and benzoylurea (BU) are prepared. Notably, the RCPDs are capable of targeting LNs for imaging. Lymphocyte homing has been demonstrated to be the cellular mechanism of RCPDs target LNs imaging. This work has developed a new nanomaterial for targeted imaging of LNs, while the biological applications of CPDs have been expanded and deepened.
An eco-friendly and convenient method is developed herein for the synthesis of S-aryl dithiocarbamates via visible-light-induced SET process of an EDA complex between thianthrenium salt functionalized arenes and dithiocarbamate anions under mild aqueous micellar conditions. This strategy indirectly realizes the method for constructing S-aryl dithiocarbamates through site-selective C−H functionalization of arenes. Most importantly, the reaction proceeded smoothly without addition of any photocatalyst, and the by-product thianthrene is recycled in quantity, ultimately minimizing the production of chemical waste. This protocol provides a promising synthesis candidate for the construction of valuable S-aryl dithiocarbamates, which also opens up a new avenue for micellar photocatalysis.
Bacterial infection is currently a serious challenge globally, causing death of thousands of human beings. New antimicrobial agents with novel mechanism of action are urgently needed. Transition metal complexes have shown great potentials in photodynamic and photocatalytic therapy. Herein, we take full advantage of metal photocatalyst and successfully developed a novel cyclometalated iridium(Ⅲ) complex (Ir1) with higher biofilm damage efficiency than the clinical antibiotics. Ir1 synergistically generates reactive oxygen species and coenzyme photocatalytic activity with high efficiency under white light irradiation. Combined with these properties, Ir1 exhibited excellent photoinactivation of S. aureus and effectively damaged the biofilm. This work provides a new approach for the development of antibacterial photodynamic therapy.
The high amount of L-lysine can increase the potential risk of cardiovascular disease. Additionally, 2-methoxy benzaldehyde (2-MB) has high toxicity and can easily pollute the environment. In this work, carbon quantum dots (CQDs) can be encapsulated into Eu-BTB (H3BTB = 1,3,5-tri(4-carboxyphenyl)benzene), forming the multi-emission composite material Eu-BTB@CQDs. It has two emissions peaks (617 nm for Eu and 470 nm for CQDs). Eu-BTB@CQDs can be applied as bi-functional ratiometric “off & on” luminescent sensor for L-lysine and 2-MB with high sensitivity and selectivity, the low limit of detection (LOD) for L-lysine is 3.68 µmol/L and for 2-MB is 0.54 µmol/L, respectively. Additionally, Eu-BTB@CQDs can quantitatively discriminate L-lysine in the mixed D- and L-lysine water solutions (five different concentrations ratio of L/D-lysine has been set) makes the chiral detection of L-lysine are more meaningful. On the other hand, Eu-BTB@CQDs also can detect 2-MB over 4-methoxybenzaldehyde (4-MB) with high selectivity. Further the detection of 2-MB and L-lysine in the lake water real samples with the reasonable recovery rate. Finally, the detection mechanisms for L-lysine and 2-MB were also investigated and discussed in detail.
Uranium and molybdenum are important strategic elements. The production of 99Mo and the hydrometallurgical process of uranium ore face difficult problems of separation of uranium and molybdenum. In this study, the four phenanthroline diamide ligands were synthesized, and extraction and stripping experiments were performed under different conditions to evaluate the potential application of these ligands for separation of U(Ⅵ) over Mo(Ⅵ). With the growth of alkyl chain, the solubility of ligands could be greatly improved, and the separation effect of U(Ⅵ) over Mo(Ⅵ) gradually increased. The SFU/Mo were around 10,000 at 4 mol/L HNO3. Three stripping agents were tested with the stripping efficiency of Na2CO3 (5%) > H2O > HNO3 (0.01 mol/L). The stripping percentages of the three stripping agents were all close to unity, indicating that the ligands had the potential to be recycled. The chemical stoichiometry of U(Ⅵ) complexes with ligands was evaluated as 1:1 using electrospray ionization mass spectrometry, ultraviolet visible spectroscopy and single-crystal X-ray diffraction. The consistency between theoretical calculation and experimental results further explains the coordination mechanism.
Direct synthesis of H2O2 from H2 and O2 via heterogeneous catalysis is an environmentally friendly and atomically economic alternative to the traditional anthraquinone oxidation (AO) process. Optimizing the electronic and geometric structures of the active metals to break the current limitations of hydrogenation rate and H2O2 selectivity is a promising and challenging topic. In this study, a series of Pd-Au bimetallic catalysts supported on TiO2 with a metal loading of 3.0 wt% and a constant Pd/Au molar ratio (Pd:Au = 2:1) were prepared. The catalysts were reduced in H2 at different temperatures (473, 573 and 673 K), and their catalytic activity for the direct H2O2 synthesis were evaluated at 283 K and 0.1 MPa. H2 reduced Pd-Au catalysts exhibited superior performance in direct H2O2 synthesis. The maximum H2O2 selectivity of 87.7% and H2O2 yield of 3116.4 mmol h−1 gPd−1 were achieved over the Pd2.0Au1.0-573 catalyst with a H2 conversion of 12.8%. The tailored local chemical environment caused by H2 reduction creates a balanced ratio of Pd0 and PdOx sites, thus improving the selectivity towards H2O2. This work developed an effective strategy for fabrication of highly active and stable Pd-based H2O2 synthesis catalysts with high H2O2 yield.
Oxygen-isotopic labelings play important roles in identifying and understanding chemical and biological processes. Direct C=O to C=18O or C=17O conversion in a single step leading to labeled compounds can alleviate synthetic burdens without the need for resynthesis. Here we describe a photocatalytic oxygen-isotopic labeling protocol that can efficiently and selectively install 18O and 17O on carbonyls of ketones and aldehydes via oxygen isotope exchange with oxygen-isotopic waters (H218O or H217O) as the sources of oxygen isotopes, in which light and oxygen-enabled sodium alkanesulfinates catalyzed this process. This strategy was extended to the in-situ formed ketones from the photocatalytic aerobic oxidation of alkyl arenes and secondary alcohols. Furthermore, reduction of the oxygen-isotopically labeled aldehydes with NaBH4 provided the corresponding oxygen-isotopically labeled primary alcohols. We believe that the oxygen-isotopically labeling method will be widely used in chemistry, biology and medicine fields.
Distortion of planar aromatics occurs in the fused rings conjugated with bulky substituents, which generates racemic enantiomers with high transformation energy barriers. However, direct synthesis of homochiral distorted aryl compounds is a very challenging task. Here, we presented a molecular folding strategy to control distorted aryl homochirality. Amino acids and their derivatives conjugated on the polycyclic aromatic hydrocarbons including benzenes, naphthalenes and triphenylenes, which formed parallel β-sheet arrays through intramolecular hydrogen bonds. The folding behavior enabled distorted or twisted geometry of aromatics, of which the handedness was associated with the absolute chirality of amino acids. X-ray crystallography, theoretical calculations and circular dichroism spectroscopy verified the distorted homochirality in the solid and solution phase. The relatively small rotational barrier between the enantiomers made the molecule sensitive to the environment and thus realized the solvent-controlled chiral inversion. The β-sheet folding strategy can be widely used in polycyclic aromatic hydrocarbons with various functions, which provided a promising strategy to control inherent chirality of aromatics with adaptive chiroptical responses.
Rhodium (Rh) has received widespread attention in fundamental catalytic research and numerous industrial catalytic applications. Compared to homogeneous catalysts, Rh-based nanomaterials as heterogeneous catalysts are much easier to separate and collect after usage, making them more suitable for commercial use. To this purpose, there has been a constant demand in constructing stable and highly active Rh-based nanomaterials. In contrast to Rh-based solid solutions with a random distribution of metallic atoms in the lattice, Rh-based intermetallic compounds (IMCs) with a fixed stoichiometric ratio and an ordered atomic arrangement can ensure the homogenous distribution of active sites and structural stability in the catalytic process. In this review, we concentrate on the fabrication of Rh-based IMCs for catalytic applications. Various synthetic methods and protocols for the controlled preparation of Rh-based IMC are illustrated. Meanwhile, the catalytic applications and corresponding catalytic mechanisms are discussed. In addition, personal perspectives about the remaining challenges and prospects in this field are provided. We believe this review will be useful in directing the development of Rh-based IMC catalysts for heterogeneous catalysis.
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