The blue glow of halides
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C(sp3)–heteroatom bond formation by iron-catalyzed soft couplings
Carbon–heteroatom bonds are of great importance due to their prevalence in pharmaceuticals, agrochemicals, materials, and natural products. Despite the effective use of metal-catalyzed cross-coupling reactions between sp2-hybridized organohalides and soft heteroatomic nucleophiles for carbon–heteroatom bond formation, the use of sp3-hybridized organohalides remain limited and the coupling with thiols remains elusive. Here, we report the coupling of sp3-hybridized benzyl or tertiary halides with soft thiol nucleophiles catalyzed by iron and extend the utility to alcohol and amine nucleophiles. The reaction is broad in substrate scope for both coupling partners and applicable in the construction of congested tri- and tetrasubstituted carbon centers as well as β-quaternary heteroatomic products. The synthetic utility is further emphasized by gram-scale synthesis and rapid herbicide library synthesis. Overall, we provide an efficient method to prepare pharmaceutically and materially relevant carbon–heteroatom bonds by expanding iron-catalyzed cross-coupling reactions to the coupling of sp3-hybridized organohalides with soft nucleophiles.
Electrically chargeable inorganic persistent luminescence in an alternating current driven electroluminescent device
Persistent luminescence (PersL) in inorganic materials, lasting from seconds to even days, has attracted considerable attention. Despite the promise of electric power-driven PersL for lighting and display device applications due to its convenience and manageability, studies on electrically driven inorganic PersL are lacking. Here, we report an inorganic PersL in electroluminescent devices, which shows an energy storage effect that persists beyond 24 h after charging with an alternating current electric field at 250 K. The spin-coating method-prepared emission layer composites consist of a small bandgap copper-doped zinc sulfide core, a high dielectric constant alumina shell and a chemically passivated dielectric polydimethylsiloxane medium (ZnS:Cu@AlOx@PDMS), and these composites exhibit well-distributed electric fields and excellent operational stability. Thermoluminescence characterization reveal that PersL with an ~ 0.3 eV trap depth in electroluminescent devices mainly arises from the charge separation via hot-electron impact excitation and charge trapping within trap states in the emission layer. This study on electrically chargeable PersL in alternating current-driven electroluminescent devices can enhance our understanding of luminescence mechanisms in inorganic semiconductors.
Amphoteric chalcogen-bonding and halogen-bonding rotaxanes for anion or cation recognition
The ever-increasing demand in the development of host molecules for the recognition of charged species is stimulated by their fundamental roles in numerous biological and environmental processes. Here, capitalizing on the inherent amphoteric nature of anisotropically polarized tellurium or iodine atoms, we demonstrate a proof of concept in charged guest recognition, where the same neutral host structure binds both cations or anions solely through its chalcogen or halogen donor atoms. Through extensive 1H nuclear magnetic resonance titration experiments and computational density functional theory studies, a library of chalcogen-bonding (ChB) and halogen-bonding (XB) mechanically interlocked [2]rotaxane molecules, including seminal examples of all-ChB and mixed ChB/XB [2]rotaxanes, are shown to function as either Lewis-acidic or Lewis-basic multidentate hosts for selective halide anion and metal cation binding. Notably, the exploitation of the inherent amphoteric character of an atom for the strategic purpose of either cation or anion recognition constitutes the inception of a previously unexplored area of supramolecular host–guest chemistry.
Enantioconvergent nucleophilic substitution via synergistic phase-transfer catalysis
Catalytic enantioconvergent nucleophilic substitution reactions of alkyl halides are highly valuable transformations, but they are notoriously difficult to implement. Specifically, nucleophilic fluorination is a renowned challenge, especially when inexpensive alkali metal fluorides are used as fluorinating reagents due to their low solubility, high hygroscopicity and Brønsted basicity. Here we report a solution by developing the concept of synergistic hydrogen bonding phase-transfer catalysis. Key to our strategy is the combination of a chiral bis-urea hydrogen bond donor (HBD) and an onium salt—two phase-transfer catalysts essential for the solubilization of potassium fluoride—as a well-characterized ternary HBD–onium fluoride complex. Mechanistic investigations indicate that this chiral ternary complex is capable of enantiodiscrimination of racemic benzylic bromides and α-bromoketones, and upon fluoride delivery affords fluorinated products in high yields and enantioselectivities. This work provides a foundation for enantioconvergent fluorination chemistry enabled through the combination of a HBD catalyst with a co-catalyst specifically curated to meet the requirement of the electrophile.
Blue benzoquinone from scorpion venom shows bactericidal activity against drug-resistant strains of the priority pathogen Acinetobacter baumannii
Antibiotic-resistant bacteria pose a significant global health threat, particularly pathogens resistant to last-resort antibiotics, such as those listed as priority pathogens by the World Health Organization. Addressing this challenge requires the development of novel antimicrobial agents. Previously, we identified a blue 1,4-benzoquinone isolated from the venom of the Mexican scorpion Diplocentrus melici as a potent antimicrobial compound effective against Staphylococcus aureus and Mycobacterium tuberculosis. Moreover, we devised a cost-effective synthetic route for its production. In this study, we demonstrate that the blue benzoquinone exhibits antibacterial activity against additional pathogens, including the priority pathogen Acinetobacter baumannii. Notably, the compound effectively killed clinical strains of A. baumannii resistant to multiple antibiotics, including carbapenem and colistin. Furthermore, A. baumannii did not develop resistance to the benzoquinone even after multiple growth cycles under sub-inhibitory concentrations, unlike the tested antibiotics. These findings underscore the potential of this blue benzoquinone as a lead compound for the development of a new class of antibiotics targeting multidrug-resistant bacteria.
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