Beyond Molecules: Mesoporous Supramolecular Frameworks Self‐Assembled from Coordination Cages and Inorganic Anions

Biological function arises by the assembly of individual biomolecular modules into large aggregations or highly complex architectures. A similar strategy is adopted in supramolecular chemistry to assemble complex and highly ordered structures with advanced functions from simple components. Here we report a series of diamond‐like supramolecular frameworks featuring mesoporous cavities, which are assembled from metal‐imidazolate coordination cages and various anions. Small components (metal ions, amines, aldehydes, and anions) are assembled into the hierarchical complex structures through multiple interactions including covalent bonds, dative bonds, and weak C? H???X (X=O, F, and π) hydrogen bonds. The mesoporous cavities are large enough to trap organic dye molecules, coordination cages, and vitamin B₁₂. The study is expected to inspire new types of crystalline supramolecular framework materials based on coordination motifs and inorganic ions.     

Spatial,Hysteretic, and Adaptive Host–Guest Chemistry in a Metal–Organic Framework with Open Watson–Crick Sites

Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site‐specific recognition takes advantage of cooperative spatial effects, as in local folding in protein–DNA binding. Herein, we report a new nucleobase‐tagged metal–organic framework (MOF), namely ZnBTCA (BTC=benzene‐1,3,5‐tricarboxyl, A=adenine), in which the exposed Watson–Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson–Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host–guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine–thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed.     

Solvent‐dependent structural dynamics of 2(1H)‐pyridinone in light absorbing S4(ππ*) state

The B‐band resonance Raman spectra of 2(1H)‐pyridinone (NHP) in water and acetonitrile were obtained, and their intensity patterns were found to be significantly different. To explore the underlying excited state tautomeric reaction mechanisms of NHP in water and acetonitrile, the vibrational analysis was carried out for NHP, 2(1D)‐pyridinone (NDP), NHP–(H₂O)_n (n = 1, 2) clusters, and NDP–(D₂O)_n (n = 1, 2) clusters on the basis of the FT‐Raman experiments, the B3LYP/6‐311++G(d,p) computations using PCM solvent model, and the normal mode analysis. Good agreements between experimental and theoretically predicted frequencies and intensities in different surrounding environments enabled reliable assignments of Raman bands in both the FT‐Raman and the resonance Raman spectra. The results indicated that most of the B‐band resonance Raman spectra in H₂O was assignable to the fundamental, overtones, and combination bands of about ten vibration modes of ring‐type NHP–(H₂O)₂ cluster, while most of the B‐band resonance Raman spectra in CH₃CN was assigned to the fundamental, overtones, and combination bands of about eight vibration modes of linear‐type NHP–CH₃CN. The solvent effect of the excited state enol‐keto tautomeric reaction mechanisms was explored on the basis of the significant difference in the short‐time structural dynamics of NHP in H₂O and CH₃CN. The inter‐molecular and intra‐molecular ESPT reaction mechanisms were proposed respectively to explain the Franck–Condon region structural dynamics of NHP in H₂O and CH₃CN.Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of a monolith functionalized with zinc oxide nanoparticles and its application in the enrichment of fluoroquinolone antibiotics

This study describes the enrichment ability of ZnO‐modified methacrylic acid‐co‐ethylene dimethacrylate polymer monoliths as stationary phases for the simultaneous determination of antibiotics (ofloxacin, ciprofloxacin, enoxacin, and pefloxacin) combined with high‐performance liquid chromatography. The prepared monolith was characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier‐transformed infrared spectroscopy, and thermogravimetric analysis. The polymer monolith microextraction method has been applied to the enrichment of fluoroquinolone antibiotics and satisfactory results were obtained in the analysis of water samples. Compared with the conventional methacrylic acid based monolith, the developed monolith exhibited a higher enrichment capacity because of the introduction of zinc oxide into the preparation process.     

Dispersive liquid–liquid microextraction based on amine‐functionalized Fe3O4 nanoparticles for the determination of phenolic acids in vegetable oils by high‐performance liquid chromatography with UV detection

A novel dispersive liquid–liquid microextraction method based on amine‐functionalized Fe₃O₄ magnetic nanoparticles was developed for the determination of six phenolic acids in vegetable oils by high‐performance liquid chromatography. Amine‐functionalized Fe₃O₄ was synthesized by a one‐pot solvothermal reaction between Fe₃O₄ and 1,6‐hexanediamine and characterized by transmission electron microscopy and Fourier transform infrared spectrophotometry. A trace amount of phosphate buffer solution (extractant) was adsorbed on bare Fe₃O₄‐NH₂ nanoparticles by hydrophilic interaction to form the “magnetic extractant”. Rapid extraction could be achieved while the “magnetic extractant” on amine‐functionalized Fe₃O₄ nanoparticles was dispersed in the sample solution by vortexing. After extraction, the “magnetic extractant” was collected by application of an external magnet. Some important parameters, such as pH and volume of extraction and desorption solvents, the extraction and desorption time needed were carefully investigated and optimized to achieve the best extraction efficiency. Under the optimal conditions, satisfactory extraction recoveries were obtained for the six phenolic acids in the range of 84.2–106.3%. Relative standard deviations for intra‐ and inter‐day precisions were less than 6.3 and 10.0%, respectively. Finally, the established method was successfully applied for the determination of six phenolic acids in eight kinds of vegetable oils.     

寡肽自组装纳米材料研究进展

肽类自组装是自然界普遍存在的分子自组装现象之一,研究其自组装行为对理解生命现象、仿生制备以及构建功能材料等具有重要的意义.寡肽由于合成简单,结构组成明确,同时具有良好的生物相容性、可控的降解性,其组装体在药物/基因控制释放、细胞培养、组织工程支架材料及生物矿化等领域具有很大的应用前景.本文概述了近年来寡肽自组装的研究进展,系统介绍了线性和环状寡肽的分子结构设计、自组装体形貌及组装机理以及组装体在生物医学等领域的应用.     

Hydrogen dangling bonds induce ferromagnetism in two-dimensional metal-free graphitic-C3N4 nanosheets

Ferromagnetic two-dimensional (2D) ultrathin nanosheets hold great promise for next generation electronics. Ferromagnetic metal-free materials that usually possess only an s/p electronic configuration with weak spin–orbit coupling and a large spin relaxation time, would play an important role in constructing future spintronic devices. However, the absence of an intrinsic spin ordering structure in most metal-free materials greatly hampers the widening scope of ferromagnetic 2D nanostructures as well as in-depth understanding of their ferromagnetic nature. Herein, the induction of intrinsic ferromagnetism in 2D metal-free g-C₃N₄ ultrathin nanosheets has been achieved through a new effective strategy whereby hydrogen dangling bonds are introduced. In our case, g-C₃N₄ ultrathin nanosheets with hydrogen dangling bonds showed obvious room temperature ferromagnetic behavior that could even be tuned by the concentration of hydrogen. This work will pave a new pathway to engineer the properties of 2D nanomaterial systems.