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.     

含氟β-氨基酸及其衍生物的合成进展

含氟β-氨基酸及其衍生物具有特殊的生理活性, 其合成方法的研究近年来受到广泛关注. 以直接氟化法和间接氟化法分类, 概述了含氟β-氨基酸及其衍生物的合成方法及最新研究进展, 对一些已知化合物的生理活性及药用价值作了初步归纳.     

Hierarchical self-assembly of bolaamphiphiles with a hybrid spacer and L-glutamic acid headgroup: pH- and surface-triggered hydrogels, vesicles, nanofibers, and nanotubes

Bolaamphiphiles with L-glutamic acid headgroups and hybrid linkers, each composed of two rigid benzene rings and different polymethylene units, were designed, and morphological controls of the hierarchical self-assemblies were realized via changing solution pH and application to solid surfaces. At a low pH of 3, bolaamphiphiles formed hydrogels with water and molecules with short and long spacers formed nanofibers and helical nanoribbon-nanotubes, respectively. In a pH 12 aqueous solution, vesicles were observed from cryo-TEM measurements for amphiphiles with short spacers that could transfer to huge vesicles when cast onto a mica surface. Amphiphiles with longer spacers self-assembled into nanoparticles in a pH 12 aqueous solution while micellar fibers were formed on a mica surface. Those assemblies were characterized with UV-vis, CD, and FT-IR spectroscopy and AFM and TEM observations. With molecular structure modification and the fine tuning of conditions, morphology transitions between various nanostructures were obtained from the self-assembled bolaamphiphiles. The environmental pH can induce different interaction modes between the headgroups, and at high pH, there are strong interactions between molecular assemblies and the mica surface. It is suggested that the active headgroups, rigid necks, and flexible linkers with different lengths render molecules with diverse aggregation morphologies.     

Theoretical analysis of initial adsorption of high-κ metal oxides on In(x)Ga(1-x)As(0 0 1)-(4×2) surfaces

Ordered, low coverage to monolayer, high-κ oxide adsorption on group III rich InAs(0 0 1)-(4×2) and In(0.53)Ga(0.47)As(0 0 1)-(4×2) was modeled via density functional theory (DFT). Initial adsorption of HfO(2) and ZrO(2) was found to remove dangling bonds on the clean surface. At full monolayer coverage, the oxide-semiconductor bonds restore the substrate surface atoms to a more bulklike bonding structure via covalent bonding, with the potential for an unpinned interface. DFT models of ordered HfO(2)/In(0.53)Ga(0.47)As(0 0 1)-(4×2) show it fully unpins the Fermi level.     

Chiral assembly of achiral pseudoisocyanine with D- and L-phenylalanine

Supramolecular chirality and molecular self-assembly are important and interesting phenomena in living and non-living systems.In this work,supramolecular chirality of achiral pseudoisocyanine(PIC) J-aggregates was successfully induced by D-,L-phenylalanine(Phe) and other amino acids in NaCl solution.The chiral J-aggregates showed a characteristic,induced circular dichroism(ICD) in the visible region of J-band chromophore which depends on the absolute configuration,concentration and side groups of α-amino ac...     

Investigations on the amalgamation of gold nanorods by iodine and the detection of tetracycline

The morphological transformation process of gold nanorods (Au-NRs) resulting from the reaction between tetracycline and iodine was monitored by the plasmon resonance absorption (PRA) spectra and the scanning electron microscope (SEM) images. It was found that iodine could fuse Au-NRs into sphericity with the lower aspect ratio and blue shift of the longitudinal PRA band. It was found, however, that the presence of tetracycline, since it can react with I₂, decreases the effective concentration of I₂ and its fusion effect on Au-NRs. As a result, the longitudinal PRA of Au-NRs shifts to longer wavelength linearly with increasing the concentration of tetracycline. With that, tetracycline can be detected in the range of 5.0×10^∮5- 5.0×10⁻⁴ mol·L⁻¹, with a limit of determination (LOD) of 2.4×10⁻⁶ mol·L⁻¹ (3σ). Most foreign substances in the samples did not interfere in the detection, and tetracycline in the synthetic samples could be detected with the recovery in the range of 92.8%–107.2%, and RSD lower than 4.3%. The concentration of tetracycline in milk detected with standard addition method was so low that it accorded with the safety regulation. Supported by the National Natural Science Foundation of China (Grant Nos. 30570465 and 20425517)     

A simple method for fabrication of sole composition nickel hexacyanoferrate modified electrode and its application

Nickel hexacyanoferrate film modified gold electrode was prepared by a simple chemical deposition procedure from a fresh prepared solution containing ferricyanide, Ni²⁺, and sodium nitrate. The resultant films have solo composition and are significantly stable as compared to the electrochemically deposited NiHCF films. For different concentrations of Na⁺ in the solution, the formal potential values of NiHCF shift according to the Nernstian behavior with a slope of 48 mV in the range of 10⁻⁴ to 1.0 M. The NiHCF film was also used for the electrocatalytic oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry increased with the ascorbic acid concentration. At a fixed potential under hydrodynamic conditions, the calibration plot was linear over the ascorbic acid concentration range 0.1-12 mM.     

Synthesis of 3-substituted 1,5-aldehyde esters via an organocatalytic highly enantioselective conjugate addition of new carbonylmethyl 2-pyridinylsulfone to enals

A highly enantioselective organocatalytic protocol for conjugate addition of new nucleophilic carbonylmethyl 2-pyridinylsulfone to enals has been developed in good yields and with high enantioselectivities. The resulting Michael adducts are versatile building blocks for a variety of organic transformations.     

Hemin-histamine-montmorillonite clay conjugate as a model biocatalyst to mimic natural peroxidase

We successfully synthesized the first hemin-montmorillonite bio-conjugate with an amino acid residue to mimic natural peroxidase enzyme. Histamine was intercalated in montmorillonite by cation exchange, then a hemin molecule was loaded onto the histamine-montmorillonite with an adsorption capacity of 7.0 mg g-1. The hemin-histamine-montmorillonite conjugate shows high peroxidase activity as indicated by the oxidation of guaiacol, which is attributed to the activation of hemin by Fe–N complex formation between the imidazole group in histamine and the iron ion in the hemin molecule. Temperature- dependent peroxidase activity for this synthesized biomimetic material indicates that raising the reaction temperature could significantly enhance the activity of the conjugate. The biomimetic catalyst has good reusability; nearly 100% activity can be retained after three cycles. Because montmorillonite clay is widely distributed in the environment, this material offers great potential for in situ and ex situ remediation of many organic contaminants in surface/subsurface soils.     

Synthesis of δ-carbolines via a Pd-catalyzed sequential reaction from 2-iodoanilines and N-tosyl-enynamines

A facile Pd-catalyzed sequential reaction has been developed for the synthesis of δ-carbolines from 2-iodoanilines and N-tosyl-enynamines. This protocol involves Larock heteroannulation/elimination/electrocyclization/oxidative aromatization cascade sequences and allows access to multisubstituted δ-carbolines in moderate to good yields.