Controlling the thermally activated delayed fluorescence of axially chiral organic emitters and their racemate for information encryption

A pair of axially chiral organic enantiomers were facilely prepared through a one-pot sequential synthesis. They exhibit circularly polarized luminescence activities and have thermally activated delayed fluorescence (TADF) and aggregation-induced emission enhancement properties. Meanwhile, these two enantiomers present remarkable and reversible thermochromism in the crystalline state, enabling dual-colour TADF switching between orange and red. However, when they form cocrystals, the resulting racemate shows opposite thermochromic behaviors. These intriguing results probably emanate from their different optical activities, leading to distinct molecular packing modes and molecular conformation variations. Moreover, information encryption based on thermochromism of organic enantiomers and their racemate has been presented for the first time. This work may expand the application scope of chiral organic luminogens and pave a new way to construct intelligent luminescent systems.

A pair of axially chiral organic enantiomers with circularly polarized thermally activated delayed fluorescence and aggregation-induced emission enhancement properties show opposite thermochromic behaviors to their racemate.     

Polymerization of olefins with a novel dinuclear ansa-zirconocene catalyst having a biphenyl bridge

Both the rac- and meso-dinuclear ansa-zirconocene catalysts (μ-C₁₂H₈{[SiPh(Ind)₂]ZrCl₂}₂) were prepared by a coupling reaction between 2 equiv of diindenylphenylchlorosilane (rac- and meso-isomers) and 1 equiv of p-dilithiobiphenyl in diethyl ether at −80°C, followed by a successive reaction with ZrCl₄ · 2THF in THF at −78°C. Polymerizations of ethene and propene were conducted in a 1 dm³ high-pressure glass reactor equipped with a mechanical stirrer at 60, 80, 100, 120, and 150°C using methylalumoxane (MAO) as cocatalyst and toluene or decahydronaphthalene as the solvent. Copolymerization of ethene and 1-octene was also checked in brief. For ethene polymerization, the meso-catalyst was found to be more active, which displayed an extremely high activity to give linear polyethene with a high molecular weight and a narrow molar mass distribution (MMD). The apparent activity increased monotonously with rising polymerization temperature from 60°C up to 150°C, indicating that the active species are stable even at a high temperature. On the other hand, both the rac- and meso-catalysts showed very poor activities for propene polymerization. However, copolymerization of ethene and 1-octene proceeded at a high speed. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2269–2274, 1998     

Synthese und Untersuchung von Hydroxylammonium‐fluorohafnaten(IV)

Synthesis and Characterization of Hydroxylammonium Fluorohafnates(IV) Two new hydroxylammonium compounds, (NH₃OH)₂HfF₆ and (NH₃OH)₃HfF₇ were isolated from the system NH₂OH/HF/HfF₄/H₂O. The compounds were prepared by dissolving Hf‐foil in aqueous hydrofluoric acid (40 % or 20 %) followed by adding of NH₂OH in ethanolic solution. The characterization was carried out by chemical, thermal, and structural analyses. The compounds are isomorphic with the hydroxylammonium fluorozirconates. Thermal analysis of (NH₃OH)₂HfF₆ and (NH₃OH)₃HfF₇ showed that they decompose in three or two steps with HfF₄ as final product.     

薄层色谱溶剂系统的优化设计

采用复合形法,根据色谱优化函数对肾上腺皮质激素类、磺胺类药物及银杏粉针剂的薄层溶剂系统进行了最优化设计。肾上腺皮质激素类药物的最佳溶剂系统为１,２－二氯乙烷－苯－甲醇（４．８１４．４２０．７８）;磺胺类药物的最佳溶剂系统为甲苯－无水乙醇－二氯乙烷－氯仿（２．３０１．４６３．３２２．９２）;银杏粉针剂的最佳溶剂系统为氯仿－甲醇－乙酸乙酯（３．３０３．２９３．４１）,实验结果与计算结果一致。     

Precise control of microstructure of functionalized polypropylene synthesized by the ansa‐zirconocene/ MAO catalysts

We inclusively investigated polymerization behavior and structure of copolymer in the copolymerization of propylene and alkylaluminum‐protected polar allyl monomers. The control of the arrangement of polar group in the copolymer was discussed. It was proved that the location of polar group could be controlled by zirconocene catalyst and a kind of polar monomer. The indenyl or the 2‐methylindenyl ligands of zirconocene were favored to produce end‐functionalized polymers. It was also found that the trimethylaluminum‐protected allylamine and triisobutylaluminum‐protected allylmercaptan had superior ability in the synthesis of end‐functionalized polypropylene. On the other hand, the 2‐methyl‐4‐phenylindenyl ligand produced the copolymers containing both the end‐polar unit and inner‐polar unit at the polymer chains. Terpolymerization of propylene, polar allyl monomer, and 5‐hexen‐1‐ol was also conducted. The NMR study of the terpolymer revealed that both the 5‐hexen‐1‐ol and the polar allyl monomer were incorporated into the polymer chain. It has also become apparent that the polar allyl monomer units predominantly occupied the chain end, while the 5‐hexen‐1‐ol units were located at the inner of main chain. Consequently, we have achieved the synthesis of functionalized polypropylene in which the arrangement of polar group was precisely controlled. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1738–1748, 2008     

First Tests of a Linear Radiofrequency Quadrupole for the Cooling and Bunching of Radioactive Light Ions

A linear radiofrequency quadrupole has been built at the LPC-Caen for the manipulation of radioactive ions. The system was designed for the cooling and bunching of a continuous beam using the buffer gas cooling technique. The technique is being extended to its ultimate limit to apply it for the cooling of light ions using H₂ as buffer gas. The bunches are to be injected into a transparent Paul trap for further decay studies. The cooling and bunching section of the system has been successfully tested off-line with a source of stable ions. We describe here the specifications of the device and present the results of the first tests.

     

Synthesis of Zeolite L. Tuning Size and Morphology

A convenient synthesis of zeolite L is presented. The size of the crystals can be tuned between 30 and 6000nm, spanning a volume range of seven orders of magnitude. The zeolite L crystals, which typically feature a cylindrical morphology, are synthesized with various aspect ratios ranging from elongated to disc-shaped. The importance of obtaining zeolite crystals with well-defined size and morphology is discussed in view of potential applications of zeolite L containing organic dye molecules as guests.