The Role of Radical Bridges in Polynuclear Single-Molecule Magnets

Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs.     

微波辅助合成Ru(Ⅱ)配合物及其自组装多层膜

运用微波辅助合成技术制备得到对称性钌(Ⅱ)配合物,对该配合物进行了¹H NMR,ESI-MS和TG分析。该钌配合物两端对称的磷酸基团可通过共价键作用组装到纳米铟锡金属氧化物导电玻璃(Indium Tin Oxides,ITO)表面,使ITO表面呈现亲水性。利用锆离子作为桥梁成功组装了钌多层膜,并对该多层膜进行了循环伏安法(Cyclic Voltammetry,CV)及紫外-可见吸收光谱法(Ultraviolet-visible absorption spectrometry,UV-Vis)等光电化学分析,实验结果表明层层自组装过程中膜沉积均匀,在0.53V出现可逆的氧化还原峰,在300~600nm的紫外可见区域出现强且宽的吸收峰,表明该钌配合物具有优良的光电性能。     

Preparation of ZSM‐5 Coated on Monolithic Interconnected Macroporous Al2O3 Using Cheap n‐Butylamine as Template

Using cheap n‐butylamine as template, ZSM‐5 zeolites have been successfully synthesized and coated on monolithic interconnected macroporous Al₂O₃ by the secondary growth method. The use of cheap n‐butylamine could significantly reduce the synthesis cost. Hierarchical monolithic ZSM‐5 zeolites were prepared from synthetic mixtures with different H₂O/Na₂O or SiO₂/Al₂O₃ ratio. The synthesized samples were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR) and N₂ adsorption‐desorption. The results show that the hierarchical monolithic zeolites were obtained with cheap n‐butylamine template as template. During the hydrothermal reaction process, the morphology of the micrometer‐sized support was well maintained. The irregular crystals were formed in a wide range of the H₂O/Na₂O or SiO₂/Al₂O₃ ratio of synthetic mixtures and coated on monolithic Al₂O₃. The relative crystallinity of the zeolites was highest at H₂O/Na₂O=250 or SiO₂/Al₂O₃=160. This type of composites exhibited hierarchical porous structures and relatively high specific surface areas.     

Deoxygenation of methyl laurate to hydrocarbons on silica-supported Ni-Mo phosphides: Effect of calcination temperatures of precursor

SiO2-supported Ni-Mo bimetallic phosphides were prepared by temperature-programmed reduction(TPR) method from the phosphate precursors calcined at different temperatures. Their properties were characterized by means of ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis DRS), H2temperature-programmed reduction(H2-TPR), X-ray diffraction(XRD), transmission electron microscopy(TEM), CO chemisorption, H2 and NH3temperature-programmed desorptions(H2-TPD and NH3-TPD). Their catalytic performances for the deoxygenation of methyl laurate were tested in a fixed-bed reactor. When the precursors were calcined at 400 and 500?C, respectively, Ni Mo P2 phase could be formed apart from Ni2 P and Mo P phases in the prepared C400 and C500 catalysts. However, when the precursors were calcined at600, 700 and 800°C, respectively, only Ni2 P and Mo P phases could be detected in the prepared C600, C700 and C800 catalysts. Also, in C400, C500 and C600 catalysts, Mo atoms were found to be entered in the lattice of Ni2 P phase, but the entering extent became less with the increase of calcination temperature. As the calcination temperature of the precursor increased, the interaction between Ni and Mo in the prepared catalysts decreased, and the phosphide crystallite size tended to increase, subsequently leading to the decrease in the surface metal site density and the acid amount. C600 catalyst showed the highest activity among the tested ones for the deoxygenation of methyl laurate. As the calcination temperature of the precursor increased, the selectivity to C12 hydrocarbons decreased while the selectivity to C11 hydrocarbons tended to increase. This can be mainly attributed to the decreased Ni-Mo interaction and the increased phosphide particle size. In sum, the structure and performance of Ni-Mo bimetallic phosphide catalyst can be tuned by the calcination temperature of precursor.     

Water‐Soluble Molecularly Imprinted Nanoparticles (MINPs) with Tailored,Functionalized, Modifiable Binding Pockets

Construction of receptors with binding sites of specific size, shape, and functional groups is important to both chemistry and biology. Covalent imprinting of a photocleavable template within surface–core doubly cross‐linked micelles yielded carboxylic acid‐containing hydrophobic pockets within the water‐soluble molecularly imprinted nanoparticles. The functionalized binding pockets were characterized by their binding of amine‐ and acid‐functionalized guests under different pH values. The nanoparticles, on average, contained one binding site per particle and displayed highly selective binding among structural analogues. The binding sites could be modified further by covalent chemistry to modulate their binding properties.     

On the Extreme Oxidation States of Iridium

It has recently been suggested that the oxidation states of Ir run from the putative ?III in the synthesized solid Na₃[Ir(CO)₃] to the well‐documented +IX in the species IrO₄⁺. Furthermore, [Ir(CO)₃]^3? was identified as an 18‐electron species. A closer DFT study now finds support for this picture: The orbitals spanned by the 6s,6p,5d orbitals of the iridium are all occupied. Although some have considerable ligand character, the deviations from 18 e leave the orbital symmetries unchanged. The isoelectronic systems from Os^?IV to Au^?I behave similarly, suggesting further possible species. To paraphrase Richard P. Feynmann “there is plenty of room at the bottom”.     

Glycosyl‐Templated Chiral Helix Stapling of Ethynylpyridine Oligomers by Alkene Metathesis between Inter‐Pitch Side Chains

Ethynylpyridine polymers and oligomers consisting of 4‐substituted pyridine rings linked by acetylene bonds at the 2‐ and 6‐positions have been investigated. Ethynylpyridine oligomers covalently linked with a glycosyl chiral template form chiral helical complexes by intramolecular hydrogen bonding, in which the chirality of the template is translated to the helix. With a view to fixation of the chiral architecture, D /L ‐galactosyl‐ and D /L ‐mannosyl‐linked ethynylpyridine oligomers have been developed with 4‐(3‐butenyloxy)pyridine units having alkene side chains. The helical structures are successfully stapled by alkene metathesis of the side chains. Subsequent removal of the chiral templates by acidolysis produces template‐free stapled oligomers. The chiral, template‐free, stapled oligomers show chiral helicity, which is resistant to polar solvents and heating.     

Iron‐Catalyzed C(sp2)H and C(sp3)H Methylations of Amides and Anilides

The so‐called magic methyl effect significantly boosts the bioactivities and physical properties of pharmacologically active drugs. Direct introduction of the methyl group by C?H activation was accomplished with a versatile iron catalyst, which enabled the C?H methylation of (hetero)benzamides, anilides, alkenes, and even alkanes by triazole assistance in a chemo‐, site‐ and diastereo‐selective fashion.     

Mechanism of Thyroxine Deiodination by Naphthyl‐Based Iodothyronine Deiodinase Mimics and the Halogen Bonding Role: A DFT Investigation

This paper deals with a systematic density functional theory (DFT) study aiming to unravel the mechanism of the thyroxine (T4) conversion into 3,3′,5‐triiodothyronine (rT3) by using different bio‐inspired naphthyl‐based models, which are able to reproduce the catalytic functions of the type‐3 deiodinase ID‐3. Such naphthalenes, having two selenols, two thiols, and a selenol–thiol pair in peri positions, which were previously synthesized and tested in their deiodinase activity, are able to remove iodine selectively from the inner ring of T4 to produce rT3. Calculations were performed including also an imidazole ring that, mimicking the role of the His residue, plays an essential role deprotonating the selenol/thiol moiety. For all the used complexes, the calculated potential energy surfaces show that the reaction proceeds via an intermediate, characterized by the presence of a X?I?C (X=Se, S) halogen bond, whose transformation into a subsequent intermediate in which the C?I bond is definitively cleaved and the incipient X?I bond is formed represents the rate‐determining step of the whole process. The calculated trend in the barrier heights of the corresponding transition states allows us to rationalize the experimentally observed superior deiodinase activity of the naphthyl‐based compound with two selenol groups. The role of the peri interactions between chalcogen atoms appears to be less prominent in determining the deiodination activity.     

Metal‐Chelating N,N′‐Bis(4‐dimethylaminophenyl)acetamidinyl Radical: A New Chromophore for the Near‐Infrared Region

A new non‐innocent ligand redox system, N,N′‐bis(4‐dimethylaminophenyl) substituted acetamidinato/acetamidinyl, has been designed and described by example of structurally and spectroscopically characterized ruthenium complexes. The hitherto unreported ligand is responsible for rather intense and narrow absorptions in the near‐infrared region of the one‐ and two‐electron oxidized forms. The spectroscopic, computational, and first structural characterization of an amidinyl radical complex adds to the list of established N‐based radical ligands.