Latest ArticlesThe enantioselective separation of racemate, particularly those containing C(sp3)-H bonds knowns for their high bond dissociation energies and significant polarity, presents a significant challenge in pharmaceutical synthesis. Recent advances have witnessed the fusion of photocatalysis with hydrogen atom transfer (HAT) methodologies, marking a notable trend in synthesis of chiral molecules. This technique uses the excitation of a catalyst to activate substrates, enabling the selective isomerization of chiral centers containing C(sp3) configurations. This process distinctively facilitates the direct activation of the C(sp3)-H bond in targeted reagents. This review systematically discusses the photocatalytic isomerization of various chiral molecule featuring C(sp3)-H centers, capable of undergoing deracemization through two primary HAT mechanisms: direct and indirect pathways. From the perspective of synthetic organic chemistry, this field has progressed towards the development of isomerization strategies for molecules that incorporate an activating group at the α-position adjacent to the C(sp3) chiral center. Moreover, it covers methodologies applicable to molecules characterized by specific C-C and C-S bond configurations. The integration of photocatalysis with HAT technology thus provides valuable strategies for the synthesis of enantiopure compounds with enhanced selectivity and efficiency.
Carbon dots (CDs) are an emerging class of zero-dimensional carbon nano optical materials that are as promising candidates for various applications. Through the exploration of scientific researchers, the optical band gap of CDs has been continuously regulated and red-shifted from the initial blue-violet light to longer wavelengths. In recent years, CDs with near-infrared (NIR) absorption/emission have been gradually reported. Because NIR light has deeper penetration and lower scattering and is invisible to the human eye, it has great application prospects in the fields of biological imaging and treatment, information encryption, optical communications, etc. Although there are a few reviews on deep red to NIR CDs, they only focus on the single biomedical direction. There is still a lack of comprehensive reviews focusing on NIR (≥700 nm) absorption and luminescent CDs and their multifunctional applications. Based on our research group’s findings on NIR CDs, this review summarizes recent advancements in their preparation strategies and applications, points out the current shortcomings and challenges, and anticipates future development trajectories.
A series of “half-sandwich” bis(imino)pyridyl iron complexes with a substituted 8-(p-X-phenyl)naphthylamine (X = OMe, Me, CF3) was designed and synthesized by combining weak π-π interaction with steric and electronic tunings. The weak noncovalent π-π interaction as well as the steric and electronic effects of bis(imino)pyridyl iron complexes were identified by experimental analyses and calculations. The roles of weak π-π interaction, steric bulk, and electronic tuning on the ethylene polymerization performance of bis(imino)pyridyl iron catalysts were studied in detail. The combination of π-π interaction with steric and electronic tunings can access to thermally stable bis(imino)pyridyl iron at 130 ℃.
Polycyclic compounds are widely found in natural products and drug molecules with important biological activities, which attracted the attention of many chemists. Phosphine-catalyzed nucleophilic addition is one of the most powerful tools for the construction of various cyclic compounds with the advantages of atom economy, mild reaction conditions and simplicity of operation. Allenolates, Morita−Baylis−Hillman (MBH) alcohols and their derivatives (MBHADs), electron-deficient olefins and alkynes are very efficient substrates in phosphine mediated annulations, which formed many phosphonium species such as β-phosphonium enolates, β-phosphonium dienolates and vinyl phosphonium ylides as intermediates. This review describes the reactivities of these phosphonium zwitterions and summarizes the synthesis of polycycle compounds through phosphine-mediated intramolecular and intermolecular sequential annulations. Thus, a systematic summary of the research process based on the phosphine-mediated sequential annulations of allenolates, MBH alcohols and MBHADs, electron-deficient olefins and alkynes are presented in Chapters 2–6, respectively.
To get large dissymmetric factor (glum) of organic circularly polarized luminescence (CPL) materials is still a great challenge. Although helical chirality and planar chirality are usual efficient access to enhancement of CPL, they are not combined together to boost CPL. Here, a new tetraphenylethylene (TPE) tetracycle acid helicate bearing both helical chirality and planar chirality was designed and synthesized. Uniquely, synergy of the helical chirality and planar chirality was used to boost CPL signals both in solution and in helical self-assemblies. In the presence of octadecylamine, the TPE helicate could form helical nanofibers that emitted strong CPL signals with an absolute glum value up to 0.237. Exceptionally, followed by addition of para-phenylenediamine, the glum value was successively increased to 0.387 due to formation of bigger helical nanofibers. Compared with that of TPE helicate itself, the CPL signal of the self-assemblies was not only magnified by 104-fold but also inversed, which was very rare result for CPL-active materials. Surprisingly, the interaction of TPE helicate with xylylenediamine even gave a gel, which was transformed into suspension by shaking. Unexpectedly, the suspension showed 40-fold stronger CPL signals than the gel with signal direction inversion each other. Using synergy of the helical chirality and planar chirality to significantly boost CPL intensity provides a new strategy in preparation of organic CPL materials having very large glum value.
Generally, gaining fundamental insights into chain processes during the combustion of flame-retardant polymers relies on the qualitative and quantitative characterization of key chain carriers. However, polymer combustion processes based on conventional solid-fuel combustion strategies, due to the high coupling of pyrolysis, combustion, soot formation and oxidation, exhibit relatively high complexity and poor flame stability, and lead to a huge obstacle to the use of optical diagnostics. Herein, a spatial-confinement combustion strategy, which can produce a special staged flame with multi-jets secondary wave, is devised to provide a highly decoupled combustion environment. Glowing soot particles are therefore decoupled from main chemiluminescence region and confined to the flame tip to provide a well-controlled, optical-thin test environment for combustion diagnostic. Based on this strategy, a multi-nozzle-separation (MNS) burner is designed and fabricated, and the combustion processes associated with four model compounds, PVC, PS, PP/TBBA blends and PP/RP blends are investigated by spontaneous spectral diagnosis, and the chemiluminescence fingerprint of key diatomic/triatomic intermediates (such as OH, CH, C2, ClO, Br2, and PHO) are clearly observed. This encouraging result means that the strategy of spatial-confinement combustion we proposed shows promising prospect in many subjects associated with combustion chain regulation, such as efficient design of flame retardants.
On-demand droplet manipulation plays a critical role in microfluidics, bio/chemical detection and micro-reactions. Acoustic droplet manipulation has emerged as a promising technique due to its non-contact nature, biocompatibility and precision, circumventing the complexities associated with other methods requiring surface or droplet pretreatment. Despite their promise, existing methods for acoustic droplet manipulation often involve complex hardware setups and difficulty for controlling individual droplet amidst multiple ones. Here we fabricate simple yet effective acoustic tweezers for in-surface and out-of-surface droplet manipulation. It is found that droplets can be transported on the superhydrophobic surfaces when the acoustic radiation force surpasses the friction force. Using a two-axis acoustic tweezer, droplets can be maneuvered along arbitrarily programmed paths on the surfaces. By introducing multiple labyrinthine structures on the superhydrophobic surface, individual droplet manipulation is realized by constraining the unselected droplets in the labyrinthine structures. In addition, a three-axis acoustic tweezer is developed for manipulating droplets in three-dimensional space. Potential applications of the acoustic tweezers for micro-reaction, bio-assay and chemical analysis are also demonstrated.
Crystalized CeO2 structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’ size and ability to absorb light. However, the controllable fabrication of well-defined hierarchical structures of CeO2 with high reactive facets is significant and challenging. Herein, a series of CeO2 supports including hierarchical flower-like (F-CeO2), ball-like (B-CeO2), cube-like (CCeO2), and rod-like CeO2(R-CeO2) supports were prepared by hydrothermal method (B-CeO2, R-CeO2 and CCeO2) or ice-bath method (F-CeO2) respectively. V atoms were selected as the active atoms and loaded on these supports. Their structure-activity relationship in photo-assisted thermal propane dehydrogenation (PTPDH) was investigated systematically. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption isotherms, and Fourier transform infrared spectrum. Results show that R-CeO2 support exhibits the biggest surface area thus achieving the best dispersion of VOx species. UV–vis spectrum and photoluminescence spectrum indicate that V/F-CeO2 has the best light adsorption property and V/R-CeO2 has the best carrier migration capacity. The activity tests demonstrate that the V/R-CeO2 has the largest net growth rate and the V/F-CeO2 has the biggest relative growth ratio. Furthermore, the non-thermal effect was confirmed by the kinetic method, which lowers the propane reaction orders, selectively promoting the first C–H bond activation. The light radiation TPSR experiment confirmed this point. DFT calculations show a good linear relationship between the energy barrier and the exchanged electron number. It inspires the design of high-reactive facets for boosting the intrinsic activity of the C–H bond in photo-assisted thermal chemical processes.
Recent advances in drug development and bioactive molecules that covalently target lysine residues have shown substantial progress. Both reversible and irreversible covalent inhibitors are developed for targeting lysine residues. The identification of protein targets and binding sites of these lysine-targeting molecules in the whole proteome is crucial to understand their proteome-wide selectivity. For covalent inhibitors, the pull down-based methods including activity-based protein profiling (ABPP) are commonly used to profile their target proteins. For covalent reversible inhibitors, it is not easy to pull down the potential protein targets as the captured proteins may get off beads because of the reversible manner. Here, we report a pair of isotope-labelled click-free probes to competitively identify the protein targets of lysine-targeting covalent reversible small molecules. This pair of isotopic probes consists of a lysine-reactive warhead, a desthiobiotin moiety and isotopicable linker. This integrated probe could eliminate the background proteins induced by the click chemistry during the pull-down process. To demonstrate the feasibility of our newly-developed probes for the protein target identification, we selected the natural product Gossypol in that we proved for the first time that it could modify the lysine residue in a covalent reversible manner. Finally, we confirmed that this pair of integrated probes can be used in a competitive manner to precisely identify the protein target as well as binding sites of Gossypol. Interestingly, pretreatment of Gossypol could stop the antibody from recognizing Gossypol-binding proteins. Together, our isotope-labeled click-free probes could be used for whole-proteome profiling of lysine-targeting covalent reversible small molecules.
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