A Nanoscale Multiresponsive Luminescent Sensor Based on a Terbium(III) Metal–Organic Framework

A nanoscale terbium‐containing metal–organic framework ( nTbL ), with a layer‐like structure and [H₂NMe₂]⁺ cations located in the framework channels, was synthesized under hydrothermal conditions. The structure of the as‐prepared sample was systematically confirmed by powder XRD and elemental analysis; the morphology was characterized by field‐emission SEM and TEM. The photoluminescence studies revealed that rod‐like nTbL exhibited bright‐green emission, corresponding to ⁵D₄→⁷F_J (J=6–3) transitions of the Tb³⁺ ion under excitation. Further sensing measurements revealed that as‐prepared nTbL could be utilized as a multiresponsive luminescent sensor, which showed significant and exclusive detection ability for Fe³⁺ ions and phenylmethanol. These results highlight the practical applications of lanthanide‐containing metal–organic frameworks as fluorescent probes.     

Tetraphenylpyrazine-based AIEgens: facile preparation and tunable light emission

Research on aggregation-induced emission (AIE) has been a hot topic. Due to enthusiastic efforts by many researchers, hundreds of AIE luminogens (AIEgens) have been generated which were mainly based on archetypal silole, tetraphenylethene, distyrylanthracene, triphenylethene, and tetraphenyl-1,4-butadiene, etc. To enlarge the family of AIEgens and to enrich their functions, new AIEgens are in high demand. In this work, we report a new kind of AIEgen based on tetraphenylpyrazine (TPP), which could be readily prepared under mild reaction conditions. Furthermore, we show that the TPP derivatives possess a good thermal stability and their emission could be fine-tuned by varying the substituents on their phenyl rings. It is anticipated that TPP derivatives could serve as a new type of widely utilized AIEgen, based on their facile preparation, good thermo-, photo- and chemostabilities, and efficient emission.     

Efficient chemoenzymatic synthesis of an N-glycan isomer library

Quantification, characterization and biofunctional studies of N-glycans on proteins remain challenging tasks due to the complexity, diversity and low abundance of these glycans. The availability of structurally defined N-glycan (especially isomer) libraries is essential to help solve these tasks. We report herein an efficient chemoenzymatic strategy, namely Core Synthesis/Enzymatic Extension (CSEE), for rapid production of diverse N-glycans. Starting with 5 chemically prepared building blocks, 8 N-glycan core structures containing one or two terminal N-acetyl-d-glucosamine (GlcNAc) residue(s) were chemically synthesized via consistent use of oligosaccharyl thioethers as glycosylation donors in a convergent fragment coupling strategy. Each of these core structures was then extended to 5 to 15 N-glycan sequences by enzymatic reactions catalyzed by 4 robust glycosyltransferases. Success in synthesizing N-glycans with Neu5Gc and core-fucosylation further expanded the ability of the enzymatic extension. Meanwhile, high performance liquid chromatography with an amide column enabled rapid and efficient purification (>98% purity) of N-glycans in milligram scales. A total of 73 N-glycans (63 isomers) were successfully prepared and characterized by MS² and NMR. In summary, the CSEE strategy provides a practical approach for “mass production” of structurally defined N-glycans, which are important standards and probes for glycoscience.     

A two‐dimensional layered CdII coordination polymer with a three‐dimensional supramolecular architecture incorporating mixed multidentate N‐ and O‐donor ligands

The combination of N‐heterocyclic and multicarboxylate ligands is a good choice for the construction of metal–organic frameworks. In the title coordination polymer, poly[bis{μ₂‐1‐[(1H‐benzimidazol‐2‐yl)methyl]‐1H‐tetrazole‐κ²N³:N⁴}(μ₄‐butanedioato‐κ⁴O¹:O^1′:O⁴:O^4′)(μ₂‐butanedioato‐κ²O¹:O⁴)dicadmium], [Cd(C₄H₄O₄)(C₉H₈N₆)]_n, each Cd^II ion exhibits an irregular octahedral CdO₄N₂ coordination geometry and is coordinated by four O atoms from three carboxylate groups of three succinate (butanedioate) ligands and two N atoms from two 1‐[(1H‐benzimidazol‐2‐yl)methyl]‐1H‐tetrazole (bimt) ligands. Cd^II ions are connected by two kinds of crystallographically independent succinate ligands to generate a two‐dimensional layered structure with bimt ligands located on each side of the layer. Adjacent layers are further connected by hydrogen bonding, leading to a three‐dimensional supramolecular architecture in the solid state. Thermogravimetric analysis of the title polymer shows that it is stable up to 529 K and then loses weight from 529 to 918 K, corresponding to the decomposition of the bimt ligands and succinate groups. The polymer exhibits a strong fluorescence emission in the solid state at room temperature.     

Hydrothermal synthesis,crystal structure and photoluminescence of two homochiral zinc(II) coordination polymers

Metal–organic frameworks (MOFs) have potentially useful applications and an intriguing variety of architectures and topologies. Two homochiral coordination polymers have been synthesized by the hydrothermal method, namely poly[(μ‐N‐benzyl‐L‐phenylalaninato‐κ⁴O,O′:O,N)(μ‐formato‐κ²O:O′)zinc(II)], [Zn(C₁₆H₁₆NO₂)(HCOO)]_n, (1), and poly[(μ‐N‐benzyl‐L‐leucinato‐κ⁴O,O′:O,N)(μ‐formato‐κ²O:O′)zinc(II)], [Zn(C₁₃H₁₈NO₂)(HCOO)]_n, (2), and studied by single‐crystal X‐ray diffraction, elemental analyses, IR spectroscopy and fluorescence spectroscopy. Compounds (1) and (2) each have a two‐dimensional layer structure, with the benzyl or isobutyl groups of the ligands directed towards the interlayer interface. Photoluminescence investigations show that both (1) and (2) display a strong emission in the blue region.     

Evolution of highly symmetric curves under the shrinking curvature flow

Under the shrinking curvature flow with inner normal velocity V = k^α(α > 1), it is shown that highly symmetric, locally convex initial curves evolve into a point asymptotically like an multi‐circles. The proof relies on a crucial use of Bonnensen inequality for highly symmetric, locally convex curves. Copyright © 2016 John Wiley & Sons, Ltd.     

Nickel‐Catalyzed Barton Decarboxylation and Giese Reactions: A Practical Take on Classic Transforms

Two named reactions of fundamental importance and paramount utility in organic synthesis have been reinvestigated, the Barton decarboxylation and Giese radical conjugate addition. N ‐hydroxyphthalimide (NHPI) based redox‐active esters were found to be convenient starting materials for simple, thermal, Ni‐catalyzed radical formation and subsequent trapping with either a hydrogen atom source (PhSiH₃) or an electron‐deficient olefin. These reactions feature operational simplicity, inexpensive reagents, and enhanced scope as evidenced by examples in the realm of peptide chemistry.     

Monotonicity,uniqueness, and stability of traveling waves in a nonlocal reaction‐diffusion system with delay

The purpose of this paper is to study the traveling wave solutions of a nonlocal reaction‐diffusion system with delay arising from the spread of an epidemic by oral‐faecal transmission. Under monostable and quasimonotone it is well known that the system has a minimal wave speed c* of traveling wave fronts. In this paper, we first prove the monotonicity and uniqueness of traveling waves with speed c ?c _?. Then we show that the traveling wave fronts with speed c >c _? are exponentially asymptotically stable.     

Contraction of the proximal mapping and applications to the equilibrium problem

In this paper, we introduce a new definition of Lipschitz-type continuity of a bifunction. Using this definition, we prove the contraction of the proximal mapping and apply it to the equilibrium problem over the fixed-point set of a nonexpansive mapping. We present a new algorithm for this problem. Under classical conditions, the convergence of the algorithm is proved. Finally, we present some numerical results for the proposed algorithm.     

Certain properties related to well posedness of switching diffusions

This work is devoted to switching diffusions that have two components (a continuous component and a discrete component). Different from the so-called Markovian switching diffusions, in the setup, the discrete component (the switching) depends on the continuous component (the diffusion process). The objective of this paper is to provide a number of properties related to the well posedness. First, the differentiability with respect to initial data of the continuous component is established. Then, further properties including uniform continuity with respect to initial data, and smoothness of certain functionals are obtained. Moreover, Feller property is obtained under only local Lipschitz continuity. Finally, an example of Lotka–Volterra model under regime switching is provided as an illustration.