Latest ArticlesCitrinsorbicillin A (1), a novel homotrimeric sorbicillinoid, along with two new monomers citrinsorbicillins B (2) and C (3), were isolated from the Coptis chinensis endophyte Trichoderma citrinoviride HT-9 by liquid chromatograph mass spectrometer (LC-MS)-guided strategy. 1 was the first trimeric-example from terrestrial fungi, which possessed a unique carbon skeleton with two bicyclo[2.2.2]octanedione ring connected through an enolated carbon forming by [4 + 2] cycloaddition. Their structures were elucidated by spectroscopic analysis and X-ray diffraction. 1 exhibited moderate cytotoxicity against human colon cancer HT29 cells, and it induced significant cell cycle arrest by reducing the protein expression of cyclin D1.
We report here the synthesis and characterization of two new members of the M2E12 family of endohedral Zintl clusters, [Fe2Sn4Bi8]3– and [Cr2Sb12]3–, both of which contain open-shell metal dimers encapsulated inside a triple-decker cluster of main-group atoms. The 75-electron [Fe2Sn4Bi8]3– cluster has a D4h-symmetric structure, while [Cr2Sb12]3–, despite having the same 75-electron count, is strongly distorted to a geometry that resembles a CrSb8 crown capped by a CrSb4 unit. The structural differences between the two are driven by the increasing availability of 3d electron density in the earlier transition metal, which leads, ultimately, to different electronic configurations in the two clusters. The trends precisely mirror those observed in the ME10 and ME12 families containing a single transition metal ion.
Electron-deficient viologens are widely used as ligands or structure-directing agents (SDAs) to synthesize crystalline X-ray induced photochromic materials. Here, a new rational strategy of anion-directed folding a flexible cation (H2imb)2+ ((H2imb)2+ = di-protonated 2,3-bis(imidazolin-2-yl)-2,3-dimethylbutane) has been developed. Electron-donating Cl− and (ZnCl4)2− are used to direct folding a flexible electron-deficient (H2imb)2+ cation. Three complexes (H2imb)(NO3)2 (1), (H2imb)Cl2·H2O (2), and (H2imb)ZnCl4 (3) have been synthesized in which (H2imb)2+ crystallize in an anti-conformation, 88.8°-gauche, and 51.8°-gauche, respectively. In contrary to X-ray silent complex 1, X-ray induced photochromism has been achieved in both complex 2 and 3. An intermolecular charge-transfer mechanism has been elucidated and the anion directed folding of (H2imb)2+ has been validated to be critical to yield colored long-lived charge-separated states.
The selective oxidative esterification of aldehydes with alcohols to the corresponding esters has been one of the hot spots in scientific research and industrial synthesis. However, the application of precious metal catalytic systems is limited by their complicated synthetic steps and high cost. Thus a highly efficient, green, recyclable selective synthesis method of esters catalyzed by polyoxovanadate (POV)-based molecular catalysts has been developed in this paper. The results show that supramolecular interaction between POV and 1,3-dibenzylimidazolium bromide (Act2Im) can efficiently convert alcohols and aldehydes to the corresponding esters in high yield under much milder conditions. Mechanistic insight is also provided based on the control experiments, single crystal X-ray diffraction and cyclic voltammetry studies.
The development of circularly polarized luminescence (CPL) materials with high performance is significantly important. Herein, we develop a facial strategy for fabricating a CPL-active system by employing an achiral luminescent metal-organic cage (MOC) and chiral boron dipyrromethene (BODIPY) molecules. CPL is achieved by taking advantage of the radiative energy transfer process, in which BODIPY molecules act as energy acceptors and MOCs act as donors. The CPL performance (maximum luminescence dissymmetry factor up to ± 1.5 × 10−3) can be tuned by adjusting the ratio between MOCs and BODIPY. White-light emission with the CPL feature is obtained by using a ternary system including MOC, chiral BODIPY, and Rhodamine B. The present work provides a facile and universal strategy to construct a CPL-active system by integrating achiral luminophores and chiral molecules.
Concise chemistry leads to a family of heptanuclear CoⅡ-clusters, [Co7(N3)12(CH3CN)12] [Y2(NO3)4(piv)4]·2CH3CN (DC1) (pivH = pivalic acid), [Co7(N3)12(CH3CN)10(NO3)0.4 (Cl)1.6]·4CH3CN (DC2) and [Co7(N3)12(CH3CN)10(NO3)2]·4CH3CN (DC3), in which the metal ions are exclusively bridged by end-on azido ligands to stabilize a beautiful disk-like topology. The resulting clusters exhibit interesting structural transformations and thermodynamically-distinct steady states verified by theoretical calculations. Magnetic studies reveal the first observation of zero-field SMM behaviour in disk-like heptanuclear CoⅡ complexes.
Palladium-based alloy catalysts have been employed as one of the potential candidates for oxygen reduction reaction (ORR), but the dissolution of transition metal hinders their application. Herein, structure ordered PdTe intermetallic with Pd shell (o-PdTe@Pd) are synthesized via an electrochemical etching driven surface reconstruction strategy. The surface reconstruction could tune the electronic structure, weaken the adsorption energy of reaction intermediates on o-PdTe@Pd, resulting in enhanced electrocatalytic activity for ORR. The mass activity of o-PdTe@Pd is about 3.3 and 2.7 times higher than that of Pd/C in acid and alkaline, respectively. Besides, the half-potentials for ORR decay only about 44 mV and 12 mV after 30 k cycles accelerated durability test in acid and alkaline media, respectively. The enhanced durability originates from the resistance of Te atoms dissolve in the ordered PdTe intermetallic core and the core-shell structure. When assembled in a Zn-air battery, o-PdTe@Pd electrode delivers a higher specific capacity (794 mAh/g) and better cycling stability than Pt/C.
Recently, organic-inorganic hybrid metal halides (HMHs) have attracted extensive attention as promising multifunctional materials by virtue of their structural diversity and tunable photophysical properties. However, it remains a challenge to design HMHs with specific functions on demand. Herein, by introducing R/S-methylbenzylamine (R/S-MBA) and doping Sb3+, we have achieved both second harmonic generation (SHG) and circularly polarized luminescence (CPL) properties in lead-free indium halides. The introduction of chiral organic cations can break the symmetry and induce the indium halides to crystallize in the chiral space group. The Sb3+ with ns2 electronic configuration can serve as the dopants to promote the formation of self-trapped excitons, so as to activate highly efficient luminescence. As a result, the as-prepared Sb3+ doped (R/S-MBA)3InCl6 show not only SHG responses but also CPL signals with luminescence dissymmetry factor of −5.3 × 10−3 and 4.7 × 10−3. This work provides a new inspiration for the exploitation of chiral multifunctional materials.
Intelligent chemical sensors have been extensively used in food safety and environmental assessment, while limited sensitivity and homogeneity bring about huge obstacles to their practical application. Herein, novel ionically conductive sensitive materials were elaborately designed based on metal ion decorated graphene oxide (GO) via a facile and general in-situ spin-coating strategy, where the abundant functional groups (-OH and -COOH) of GO layer could provide natural binding sites for various bivalent metal cations (such as Cu2+, Ni2+, Zn2+, Co2+, and Mg2+) through coordination and electrostatic interaction. The intercalated metal cations on the layered GO nanosheets can be regarded as charge carriers and complexation with targeted gas (cadaverine, Cad), which is a typical metabolites production and food degradants. By contrast, the designed GO@Cu(Ⅱ) sensor exhibited the optimal sensing performance toward Cad molecules at room temperature, including ultra-low detection limit (ca. 3 nL), excellent sensitivity, and rapid low concentration detection rate (only 16 s). Interestingly, the sensor exhibited an irreversible and specific response toward Cad, while it showed a transient and reversible response to other interfering gases, implying its outstanding selectivity. In addition, the GO@Cu(Ⅱ) sensor enabled real-time monitoring of the decay progression of cheese, and it exhibited great potential for large-scale production via its excellent homogeneity. It provides an efficient approach to tailoring intelligent chemical sensors for real-time food safety monitoring and human health warning.
Electrocatalysis is a surface-sensitive process, in which the catalytic activity of electrocatalyst highly relates to the surface adsorption/desorption behaviors of the reactants/intermediates/products on the catalytically active sites. Surface chemical microenvironment engineering via organic molecules functionalization is a promising strategy to tune the electrocatalytic activity since it can well modify the electrode/electrolyte interface and alter the reaction pathways. In this review, we summarize the recent progress of surface microenvironment engineering of electrocatalysts induced by organic molecules functionalization, with the special focus on the organic molecule-assisted growth mechanism and unique electronic effect. More importantly, the applications of organic molecule functionalized catalysts in various electrocatalytic reactions are also systematically summarized, along with a deep discussion on the conclusion and perspective. This work will open a new avenue for the construction and modification of advanced electrocatalysts based on organic molecule-mediated interface engineering.