Discrete Rectangles,Prisms, and Heterometallic Cages from a Conjugated Cp*Rh‐Based Building Block

By carefully selecting an existing synthetic strategy and suitable coordination subunits, constructing desired coordination geometries is no longer that difficult to accomplish. Herein, a new strategy to construct a series of unprecedented structures by using conjugated Cp*Rh‐based complex BN‐OTf (Cp*=η⁵‐C₅Me₅) as the building block is proposed. DFT calculations revealed extensive delocalized π bonds in the subunit. With BN‐OTf , rectangular macrocycles TN‐bpy and TN‐bpe were controllably synthesized. Single‐crystal XRD studies confirmed one‐dimensional stacking channels for the tetranuclear structure. Notably, the starting ligand imidazole‐4,5‐dicarboxylate was found to act not only as a tetradentate but also as a hexadentate ligand that can coordinate to further metal ions. Subsequently, [4 Rh+1 M] heterometallic complexes HMZ (M=Cu and Zn) were accessed by chelating borderline hard/soft Lewis acids. With TN‐Linker or HMZ , two routes resulted in the [8 Rh+2 M] heterometallic cages HMC (M=Cu and Zn) with excellent crystallinity and stability. Surprisingly, when BN‐OTf bonded to rhodium itself, triangular prisms TP‐Linker were obtained with high solubility after being linked by bipyridine linkers. Both the X‐ray structure and ¹H NMR spectrum confirmed the novel isomerization of the triangular structures. All of the compounds were obtained in high yields and were fully characterized by ¹H NMR spectroscopy, elemental analysis, IR spectroscopy, and in most cases single‐crystal X‐ray structure determination.     

Synthesis and biological activity of novel phenyltriazolinone derivatives

Phenyltriazolinones are one of the most important classes of herbicides targeting the protoporphyrinogen oxidase enzyme. A series of triazolinone derivatives containing a strobilurin pharmacophore were designed and synthesized with the aim of discovering new phenyltriazolinone analogues with high activity. The herbicidal activity of the synthesized compounds was assayed and some of the test compounds displayed moderate herbicidal activity at 150 g ai/ha.     

Oligomers of a 5-carboxy-methanopyrrolidine β-amino acid. A search for order

CD spectra for homooligomers (n = 4, 6, 8) of (1S,4R,5R)-5-syn-carboxy-2-azabicyclo[2.1.1]hexane (MPCA), a methano-bridged pyrrolidine β-carboxylic acid, suggest an ordered secondary structure. Even in the absence of internal hydrogen bonding, solution NMR, X-ray, and in silico analyses of the tetramer are indicative of conformations with trans-amides and C(5)-amide-carbonyls oriented toward the C(4) bridgehead. This highly constrained β-amino acid could prove useful in the ongoing development of well-defined foldamers.     

Real-time monitoring of induced adaptation of redox active Escherichia coli biofilm by EQCM-controlled extracellular redox environment

In this paper we report the anaerobic Escherichia coli biofilm formation on solid substrate under redox-controlled extracellular environment by an electrochemical quartz crystal microbalance (EQCM) method. Both biomass and electrochemical activity were monitored in situ. Larger biomass was yielded under redox-controlled condition comparing with natural biofilm growth, which was also confirmed by optical observation. Surface-colonizing cells responded more sensitively to their redox environment than planktonic cells. Cyclic voltammogram (CV) obtained during the time course of biofilm development indicates the emergence of redox active phenotype under redox-controlled condition but not in natural condition. Our results suggest an effective means to control biofilm development with desired metabolic adaptation and also to in situ monitor the biomass yield and the emergent catalytic property simultaneously.     

Antibacterial Constituents from Isodon Excisoides

Two new ent‐kaurane diterpenoids, taihangexcisoidesin C (1) and its acetonide, taihangexcisoidesin D (2), along with 9 known compounds were isolated from the leaves of Isodon excisoides. The structures of the new compounds were elucidated using 1D and 2D NMR spectroscopy analysis. Compounds 3‐6 and 8‐9 were tested for their antibacterial activity against Escherichia coli, Staphylococcus aureus, S. epidermidis and S. saprophyticus. Compound 6 showed inhibitory effects on Staphylococcus aureus, S. epidermidis and S. saprophyticus MIC values 32, 16 and 16 μg/mL, respectively. All of the compounds didn't show effects on Escherichia coli (MIC > 10 mg/mL).     

Structural and electrochemical properties of high-capacity Ml-Mg-Ni-based hydrogen storage alloys

The Ml-Mg-Ni-based (Ml = La-rich mixed lanthanide) hydrogen storage alloy Ml_0.88Mg_0.12Ni_3.0-Mn_0.10Co_0.55Al_0.10 was prepared by inductive melting. The micro-structure was analyzed by XRD and SEM. The alloy consists mainly of CaCu₅-type phase, Ce₂Ni₇-type phase and Pr₅Co₁₉-type phase. The electrochemical measurements show that the maximum discharge capacity is 386 mAh/g, 16.3% higher than that of the commercial AB₅-type alloy (332 mAh/g). At discharge current density of 1 100 mA/g, high rate dischargeability is 62%, while that of the AB5-type alloy is only 45%. The discharge capacity decreases to 315 mAh/g after 300 charge/ discharge cycles, 81.5% of the maximum discharge capacity. __________ Translated from Journal of Xi’an Jiao Tong University, 2008, 42(3) (in Chinese)     

Fabrication of a high-strength hydrogel with an interpenetrating network structure

Hydrogels have potential applications in many fields, but the poor mechanical strength has limited their further development. In this article, we designed a high-strength hydrogel with an interpenetrating network (IPN) structure from polyacrylamide (PAM) and poly(vinyl alcohol) (PVA). Synthesis parameters, such as PVA/AM mass ratio, crosslinker dosage and elongation time were carried out for high tensile strength and elongation. The results showed that chemical crosslinking, physical entanglement and PVA precipitates were the dominant parameters for the improvement of mechanical properties. The PVA structure transferred from crystal to amorphous due to intermolecular and intramolecular interactions (such as hydrogen bond and self-crosslinking). PVA precipitates scatterred in the brittle PAM matrix homogeneously which dispersed the applied stress and improved the hydrogel toughness. The tensile strength and elongation were extremely high, they were 2.4 MPa and 3100%, respectively. The simple method is versatile in synthesizing high-strength IPN hydrogels using many kinds of polymer species.     

Cobalt(II)‐Catalyzed C?H Alkynylation/Annulation with Terminal Alkynes: Selective Access to 3‐Methyleneisoindolin‐1‐one

A highly efficient cobalt(II)‐catalyzed alkynylation/annulation of terminal alkynes assisted by an N,O‐bidentate directing group is described. This protocol is characterized by wide substrate scope utilizing cheap cobalt catalysts, and offers a new approach to 3‐methyleneisoindolin‐1‐one, which can be converted into an oxadiazine salt in one step. Moreover, the directing group could be removed in three steps.     

基于蛋白质骨架的人工水解酶的理性设计

蛋白质是生命体的重要组成部分,其中生物酶在生命体系中发挥至关重要的作用。蛋白质分子设计是研究生物酶结构与功能关系的重要手段。本文综述了基于蛋白质骨架的人工水解酶的理性设计与功能研究进展,包括对天然蛋白的重新利用和重新改造,基于3-股螺旋、4-股螺旋或锌指蛋白的分子设计,以及血红蛋白(如细胞色素b₅和肌红蛋白突变体)水解酶催化活性的调控等,阐明了人工水解酶分子设计的基本思路与研究方法,为合理构建人工水解酶或其他生物酶提供了重要的信息。人工水解酶的理性设计进展,不但深化我们对天然酶结构-性质-反应-功能关系的认识,而且还提升我们创造具有优越功能的人工生物酶的能力。     

Carteraol E, a potent polyhydroxyl ichthyotoxin from the dinoflagellate Amphidinium carterae

Carteraol E (1), C₇₄H₁₂₆O₂₄, a polyhydroxyl ichthyotoxin, was isolated from the lab-cultured marine dinoflagellate Amphidinium carterae. Carteraol E possessed three tetrahydropyrans, and 19 hydroxyl groups on a C69-linear aliphatic chain with a ketone moiety, an exo-methylene, and three methyl branches. The structure was elucidated by extensive analyses of 2D NMR spectra. Cateraol E exhibited potent ichthyotoxicity with LD₅₀ value of 0.28 μM, and antifungal activity against Aspergillus niger.