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.     

Photolithographic Encoding of Metal Complexes

A platform technology for the creation of spatially resolved surfaces encoded with a monolayer consisting of different metal complexes was developed. The concept entails the light‐triggered activation of a self‐ assembled monolayer (SAM) of UV‐labile anchors, that is, phenacylsulfides, and the subsequent cycloaddition of selected diene‐functionalized metal complexes at defined areas on the surface. The synthesis and characterization of the metal complexes for the UV‐light assisted anchoring on the surface and a detailed study of a short‐chain oligomer model system in solution confirm the high efficiency of the photoreaction. The hybrid materials obtained by this concept can potentially be utilized for the design of highly valuable catalytic or (opto‐)electronic devices.     

Reversible Assembly of a Supramolecular Cage Linked by Boron–Nitrogen Dative Bonds

Boron–nitrogen dative bonds provide a suitable motif for reversible, yet strong and directed interactions, leading to the highly efficient self‐assembly of small organic building blocks into supramolecular cage structures. A bipyramidal [2+3] assembly, as the first example of a supramolecular cage mediated by B?N dative bonds that exists as a discrete species in solution, is quantitatively obtained from a tribenzotriquinacene‐based trisboronate ester and 1,4‐diazabicyclo[2.2.2]octane. Thermodynamic equilibria of cage formation are investigated by isothermal titration calorimetry and fully reversible cage opening can be observed at elevated temperatures.     

Efficient Automated Solid‐Phase Synthesis of DNA and RNA 5′‐Triphosphates

A fast, high‐yielding and reliable method for the synthesis of DNA‐ and RNA 5′‐triphosphates is reported. After synthesizing DNA or RNA oligonucleotides by automated oligonucleotide synthesis, 5‐chloro‐saligenyl‐N,N‐diisopropylphosphoramidite was coupled to the 5′‐end. Oxidation of the formed 5′‐phosphite using the same oxidizing reagent used in standard oligonucleotide synthesis led to 5′‐cycloSal‐oligonucleotides. Reaction of the support‐bonded 5′‐cycloSal‐oligonucleotide with pyrophosphate yielded the corresponding 5′‐triphosphates. The 5′‐triphosphorylated DNA and RNA oligonucleotides were obtained after cleavage from the support in high purity and excellent yields. The whole reaction sequence was adapted to be used on a standard oligonucleotide synthesizer.     

Highly Dense Isolated Metal Atom Catalytic Sites: Dynamic Formation and In Situ Observations

Atomically dispersed noble‐metal catalysts with highly dense active sites are promising materials with which to maximise metal efficiency and to enhance catalytic performance; however, their fabrication remains challenging because metal atoms are prone to sintering, especially at a high metal loading. A dynamic process of formation of isolated metal atom catalytic sites on the surface of the support, which was achieved starting from silver nanoparticles by using a thermal surface‐mediated diffusion method, was observed directly by using in situ electron microscopy and in situ synchrotron X‐ray diffraction. A combination of electron microscopy images with X‐ray absorption spectra demonstrated that the silver atoms were anchored on five‐fold oxygen‐terminated cavities on the surface of the support to form highly dense isolated metal active sites, leading to excellent reactivity in catalytic oxidation at low temperature. This work provides a general strategy for designing atomically dispersed noble‐metal catalysts with highly dense active sites.     

Native Mannose‐Dominant Extraction by Pyridine–Phenol Alternating Oligomers Having an Extremely Efficient Repeating Motif of Hydrogen‐Bonding Acceptors and Donors

Pyridine–phenol alternating oligomers in which pyridine and phenol moieties are alternatingly linked through acetylene bonds at the 2,6‐positions of the aromatic rings were designed and synthesized. The pyridine nitrogen atom and the neighboring phenolic hydroxyl group were oriented so that they do not form an intramolecular hydrogen bond but cooperatively act as hydrogen‐bonding acceptor and donor in a push–pull fashion for the hydroxyl group of saccharides. The longer oligomer strongly bound to lipophilic glycosides in 1,2‐dichloroethane, and association constants approached 10⁸ M ^?1. Moreover, the oligomer extracted native saccharides from a solid phase to apolar organic solvents up to the extent of an equal amount of the oligomer and showed mannose‐dominant extraction among naturally abundant hexoses. The oligomer bound to native saccharides even in 20 % DMSO‐containing 1,2‐dichloroethane and exhibited association constants of greater than 10 M ^?1 for D ‐mannose and D ‐glucose.     

Green Approach to the Fabrication of Superhydrophobic Mesh Surface for Oil/Water Separation

We report a simple and environment friendly method to fabricate superhydrophobic metallic mesh surfaces for oil/water separation. The obtained mesh surface exhibits superhydrophobicity and superoleophilicity after it was dried in an oven at 200 °C for 10 min. A rough silver layer is formed on the mesh surface after immersion, and the spontaneous adsorption of airborne carbon contaminants on the silver surface lower the surface free energy of the mesh. No low‐surface‐energy reagents and/or volatile organic solvents are used. In addition, we demonstrate that by using the mesh box, oils can be separated and collected from the surface of water repeatedly, and that high separation efficiencies of larger than 92 % are retained for various oils. Moreover, the superhydrophobic mesh also possesses excellent corrosion resistance and thermal stability. Hence, these superhydrophobic meshes might be good candidates for the practical separation of oil from the surface of water.     

Buckycatcher polymer versus fullerene‐buckycatcher complex: Which is stronger?

The C₆₀H₂₈ buckycatcher (BC) is an excellent host for fullerenes. This receptor features two corannulene pincers which trap C₆₀/C₇₀ via π stacking interactions. Although, the formation of C₆₀@C₆₀H₂₈ complexes is readily observed, the dimerization of C₆₀H₂₈ is not a competitive process, even at high concentrations. By means of first principle calculations, we have studied the thermodynamics of the polymerization of BCs and the formation of fullerene complexes. The results obtained with the M06‐2X, B97‐D, B3LYP‐D3BJ, PBE‐D2, and PBE‐D3 functionals indicated that the interaction energy of (C₆₀H₂₈)₂ is larger than the one computed for C₆₀@C₆₀H₂₈, by 8–10 kcal/mol. Because of the greater number of atoms, and due to the presence of more hydrogens, the inclusion of free energy corrections lowers the energetic separation between (C₆₀H₂₈)₂ and C₆₀@C₆₀H₂₈, even though the dimer maintains its position as being slightly more bound than that of the C₆₀@C₆₀H₂₈. Our calculations indicated that up to the C₆₀H₂₈ trimer could be formed with a free energy change larger than that corresponding to the dimerization and fullerene complexation processes. Finally, we found that the inversion of the corannulene pincers attached to the cyclooctatetraene core is 2–3 kcal/mol lower than that corresponding to free corannulene. We expect that this work can motivate new investigations that may lead to the observation of C₆₀H₂₈ polymers. © 2015 Wiley Periodicals, Inc.     

New Cu(I) Coordination Complexes Based on Tetrathiafulvalene Substituted Triazol‐pyridine Ligand: Synthesis,Properties and Theoretical Studies

Two Cu(I) complexes based on the thioethyl‐bridged triazol‐pyridine ligand with tetrathiafulvalene unit (TTF‐TzPy, L ), [Cu(I)(Binap)(L)]BF₄ ( 5 , Binap=2,2’‐bis(diphenylphosphino)‐1,1’‐binaphthyl) and [Cu(I)(Xantphos)(L)]BF₄ ( 6 , Xantphos=9,9‐dimethyl‐4,5‐bis(diphenylphosphino)‐xanthene), have been synthesized. All new compounds are characterized by elemental analyses, ¹H NMR and mass spectroscopies. The complex 5 has been determined by X‐ray structure analyses which shows that the central copper (I) ion assumes distorted tetrahedral geometry. The photophysical, computational and electrochemical properties of L and 5 ‐ 6 have been investigated. The most representative molecular orbital energy‐level diagrams and the spin‐allowed singlet? singlet electronic transitions of the three compounds have been calculated with density functional theory (DFT) and time‐dependent DFT (TD‐DFT). The luminescence bands of Cu(I) complexes 5 ‐ 6 have been assigned as mixed intraligand and metal‐to‐ligand charge transfer ³(MLCT+π→π^*) transitions through analysis of the photophysical properties and DFT calculations. The electrochemical studies reveal that 5 ‐ 6 undergo reversible TTF/TTF^+?/TTF²⁺ redox processes and one irreversible Cu⁺→Cu²⁺ oxidation process.     

PEG化的聚合物载体树脂研究进展

组合化学已成为发现和优化新药、亲和配体和催化过程中的重要组成部分.高分子载体树脂在组合化学中起着关键的作用,各种类型的聚合物树脂在有机合成中已被广泛开发为载体、反应物和催化剂.与传统的Merrifield树脂相比较,聚乙二醇(PEG)化的聚合物树脂具有与极性溶剂更好的相容性、更高的溶剂吸收和溶胀性能.本文主要综述与PEG相关联的聚合物树脂在有机合成载体领域中的最新成果.