DDQ induced oxidative cyclisations of 1,2-dihydronaptho[2,1-b]furans

The DDQ mediated oxidative cyclisation reactions of a series of dihydronaptho[2,1-b]furans were examined. In the presence of an acid catalyst, the reaction yielded polycyclic ethers and lactones in good to excellent yields.     

Modulation of Aggregation‐Induced Emission and Electroluminescence of Silole Derivatives by a Covalent Bonding Pattern

The deciphering of structure–property relationships is of high importance to rational design of functional molecules and to explore their potential applications. In this work, a series of silole derivatives substituted with benzo[b]thiophene (BT) at the 2,5‐positions of the silole ring are synthesized and characterized. The experimental investigation reveals that the covalent bonding through the 2‐position of BT (2‐BT) with silole ring allows a better conjugation of the backbone than that achieved though the 5‐position of BT (5‐BT), and results in totally different emission behaviors. The silole derivatives with 5‐BT groups are weakly fluorescent in solutions, but are induced to emit intensely in aggregates, presenting excellent aggregation‐induced emission (AIE) characteristics. Those with 2‐BT groups can fluoresce more strongly in solutions, but no obvious emission enhancements are found in aggregates, suggesting they are not AIE‐active. Theoretical calculations disclose that the good conjugation lowers the rotational motions of BT groups, which enables the molecules to emit more efficiently in solutions. But the well‐conjugated planar backbone is prone to form strong intermoelcular interactions in aggregates, which decreases the emission efficiency. Non‐doped organic light‐emitting diodes (OLEDs) are fabricated by using these siloles as emitters. AIE‐active silole derivatives show much better elecroluminescence properties than those without the AIE characterisic, demonstrating the advantage of AIE‐active emitters in OLED applications.     

GCD matrices,posets, and nonintersecting paths

We show that with any finite partially ordered set P (which need not be a lattice) one can associate a matrix whose determinant factors nicely. This was also noted by D.A. Smith, although his proof uses manipulations in the incidence algebra of P while ours is combinatorial, using nonintersecting paths in a digraph. As corollaries, we obtain new proofs for and generalizations of a number of results in the literature about GCD matrices and their relatives.     

The Synthesis and Characterization of a New Layered Chlorozincophosphate Zn(HPO4)Cl[C4H10N]

Along a systematic study of open-framework materials aiming at producing new molecular sieves, we characterized a new zincophosphate Zn(HPO₄)Cl[C₄H₁₀N]. It was synthesized under mild conditions (r.t.) in the presence of pyrrolidinium as an organic-structure directing agent. The structure of this compound, determinated by single crystal X-ray diffraction, consists of anionic parallel [Zn(HPO₄)Cl]^? sheets alternating with thick slabs of organic molecules (C₄H₁₀N)⁺. These latters are linked to the anionic sheets through hydrogen bonds. Zn(HPO₄)Cl[C₄H₁₀N] crystallizes in the monoclinic system and the space group C2/c (No. 9) with cell parameters a = 24,83(9), b = 9,258(5), c = 8.778(3), β = 110,45(4), Z = 8, V = 1891.0(14) Åt³, R = 0.045, and R_w = 0.07. Solid state ³¹P and ¹³C MAS NMR spectroscopies are in agreement with the X-ray structure.     

A New Strategy toward “Simple” Water‐Soluble AIE Probes for Hypoxia Detection

Hypoxia‐responsive fluorescent probes have emerged as a novel scaffold for tumor diagnosis. However, dilemma often exists between simple synthesis and high water solubility in traditional probes. Owing to the intrinsic property of N‐oxides, herein, a new strategy is proposed to design and synthesize probes for in vitro hypoxia imaging. Equipped with tetraphenylethene (TPE), the N‐oxides exhibit aggregation‐induced emission characteristics and emit no light in aqueous solutions. Interestingly, the N‐oxides can be reduced by ferrous ions in different rates. The aggregation of the resulting hydrophobic TPE residues restricts the intramolecular motions of the molecules, which “turns‐on” their fluorescence. The N? O covalent bond of one molecule can be specifically cleaved by cellular reductase overexpressed under hypoxic conditions, and thus turn‐on hypoxia imaging in vitro is achieved. The new strategy to design hypoxia imaging probes is extremely valuable and has great potential for application in tumor diagnosis.     

Antioxidative and DNA Protective Effects of Bacillomycin D-Like Lipopeptides Produced by B38 Strain

In the present study, we evaluated the antioxidant and the scavenging ability of C14, C15 and C16 bacillomycin D-like lipopeptides produced by B38 strain. They all displayed strong reducing power activity, hydroxyl and superoxide anion radicals scavenging activities and inhibition of lipid peroxidation. In addition, they were found to protect plasmid DNA damage from hydroxyl radical oxidation. Data suggested that their antioxidant potency can be attributed to the hydrophobic and aromatic side-chain groups of their amino acids as well as to the aliphatic chain of their beta amino fatty acids. Note that the hydrocarbon chain length did not interfere with the antioxidant power. Overall, such bacillomycin D lipopeptides which exhibit antioxidant and radical scavenging activities may be useful for cosmetic, therapeutic or pharmaceutical purposes in order to delay or prevent oxidative deterioration of manufactured products.