Alkylation of Allyl/Alkenyl Sulfones by Deoxygenation of Alkoxyl Radicals

A challenging deoxygenation of alkoxyl radicals from readily accessible alcohol derivatives was developed, affording facile synthesis of functionalized alkenes with good functional group tolerance under mild reaction conditions. Because alkoxyl radicals can easily undergo β-fragmentations or hydrogen abstractions, this new strategy for deoxygenation of alkoxyl radicals is highly valuable. Moreover, mechanistic studies revealed that the electron-neutral phosphine acts as the deoxygenation reagent.     

Design of and Stability Studies on Trefoil Knots Featuring RhCp* Building Blocks

Four flexible ligands with different lengths, degrees of flexibility, and steric bulk were synthesized and used to prepare metal-directed assemblies. Interestingly, minor differences among the ligands led to products with dramatically different topologies: a binuclear D -shaped macrocycle, tetranuclear rectangles, and hexanuclear trefoil knots. The interconversion of the trefoil-shaped complexes was also investigated. This contribution introduces a rare ligand-controlled trefoil–rectangle shape transformation in solution.     

Imide-Functionalized Polymer Semiconductors

Imide-functionalized π-conjugated polymer semiconductors have received a great deal of interest owing to their unique physicochemical properties and optoelectronic characteristics, including excellent solubility, highly planar backbones, widely tunable band gaps and energy levels of frontier molecular orbitals, and good film morphology. The organic electronics community has witnessed rapid expansion of the materials library and remarkable improvement in device performance recently. This review summarizes the development of imide-functionalized polymer semiconductors as well as their device performance in organic thin-film transistors and polymer solar cells, mainly achieved in the past three years. The materials mainly cover naphthalene diimide, perylene diimide, and bithiophene imide, and other imide-based polymer semiconductors are also discussed. The perspective offers our insights for developing new imide-functionalized building blocks and polymer semiconductors with optimized optoelectronic properties. We hope that this review will generate more research interest in the community to realize further improved device performance by developing new imide-functionalized polymer semiconductors.     

Enantioselective C2-Alkylation of Indoles through a Redox-Relay Heck Reaction of 2-Indole Triflates

A palladium-catalyzed enantioselective redox-relay Heck reaction of 2-indole triflates and disubstituted alkenes is reported. This process combines readily available indole triflates with a variety of alkenes to afford a range of indole derivatives bearing a stereocenter adjacent to C2. Enantioselectivity is achieved through use of a simple pyridine-oxazoline ligand. Tuning the electronics of the indole, through judicious choice of N-protecting group, is required to ensure selective β-hydride elimination away from the indole core. Utility of this method is highlighted in a modular formal synthesis of an S1P₁ agonist precursor developed by Merck.     

Directing-Group-Free C7-Alkylations of N-Alkylindoles Mediated by Cationic Zirconium Complexes: Role of Brønsted Acid for Catalytic Manifold

Highly position selective alkylations of N-alkylindoles at C7-positions have been enabled by cationic zirconium complexes. The strategy provides a straightforward access to install alkyl groups at C7-positions of indoles without a complex directing group. Mechanistic studies provided support for the importance of Brønsted acids in the catalytic manifold.     

Bis-tridentate IrIII Phosphors Bearing Two Fused Five-Six-Membered Metallacycles: A Strategy to Improved Photostability of Blue Emitters

Iridium complexes bearing chelating cyclometalates are popular choices as dopant emitters in the fabrication of organic light-emitting diodes (OLEDs). In this contribution, we report a series of blue-emitting, bis-tridentate Ir^III complexes bearing chelates with two fused five-six-membered metallacycles, which are in sharp contrast to the traditional designs of tridentate chelates that form the alternative, fused five-five metallacycles. Five Ir^III complexes, Px-21 – 23 , Cz-4 , and Cz-5 , have been synthesized that contain a coordinated dicarbene pincer chelate incorporating a methylene spacer and a dianionic chromophoric chelate possessing either a phenoxy or carbazolyl appendage to tune the coordination arrangement. All these tridentate chelates afford peripheral ligand–metal–ligand bite angles of 166–170°, which are larger than the typical bite angle of 153–155° observed for their five-five-coordinated tridentate counterparts, thereby leading to reduced geometrical distortion in the octahedral frameworks. Photophysical measurements and TD-DFT studies verified the inherent transition characteristics that give rise to high emission efficiency, and photodegradation experiments confirmed the improved stability in comparison with the benchmark fac-[Ir(ppy)₃] in degassed toluene at room temperature. Phosphorescent OLED devices were also fabricated, among which the carbazolyl-functionalized emitter Cz-5 exhibited the best performance among all the studied bis-tridentate phosphors, showing a maximum external quantum efficiency (EQE_max) of 18.7 % and CIE_x,y coordinates of (0.145, 0.218), with a slightly reduced EQE of 13.7 % at 100 cd m⁻² due to efficiency roll-off.     

Liquid crystalline behaviours of some 3-perfluoroalkylbenzoate esters

A series of 3-perfluoroalkylbenzoate esters are synthesised. They tend to exhibit enantiotropic SmA and SmC phases. The clearing points are decreased with increasing the alkoxy chain length and show odd-even effect. With increasing the fluorocarbon chain length, the melting and clearing points increase; however, the SmC phase is suppressed.     

高能量密度型锂离子电池正极材料LiNi0.5Mn1.5O4改性的研究进展

尖晶石镍锰酸锂(LiNi0.5Mn1.5O4)具有工作电压高、结构稳定、适合快充快放等特性成为高能量及高功率密度型正极材料的有力竞争者.结合了近几年的研究报道,介绍了LiNi0.5 Mn1.5O4的结构、制备方法、改性方法及其应用前景,着重介绍了LiNi0.5 Mn1.5O4材料晶型结构对其性能的影响,并指出该材料目前存在的问题和研究重点.