Highly Tin‐Selective Stille Coupling: Synthesis of a Polymer Containing a Stannole in the Main Chain

The incorporation of heavier Group 14 element heteroles into semiconducting polymers leads to unusual optoelectronic properties. However, polymers containing stannoles have not been accessible to date. We report a synthetic route to a well‐defined, stannole‐containing polymer, the first example of this class of π‐conjugated polymers. This route was made possible by developing difunctionalized stannole monomers and highly tin‐selective Stille coupling reactions that leave the tin in the stannole untouched. Compared to poly(3‐n‐hexylthiophene), the resulting polymer displays a remarkable bathochromic shift in its absorption.     

Synthesis of a C(sp2)-bridged Phosphine-Borane by Ionic Coupling

The vinyl carbenoid H₂C=CBr(Li) has been used as key precursor to prepare a geminal C(sp²)-bridged phosphine-borane. Starting from bromoethene, two sequences of lithiation/electrophilic trapping, with ClPiPr₂ and FBMes₂ respectively, affords iPr₂P–C(=CH₂)–BMes₂ 3 [Mes = 2,4,6-(H₃C)₃C₆H₂]. This new phosphine-borane 3 was characterized by multi-nuclear NMR and mass spectroscopy. It adopts a monomeric open structure without P→B interaction. A few crystals of a secondary product 4 were analyzed by X-ray diffraction, revealing an unusual dimeric structure.     

Theoretical investigations of spin-orbit coupling and intersystem crossing in reaction carbon dioxide activated by [Re(CO)2]+

In order to further explore the detailed reaction mechanism of carbon dioxide activated by [Re(CO)₂]⁺ complex, CCSD(T) methods was performed to determine related potential energy surface (PES). Crossing point is determined by using a partially optimized method. The result shows that larger spin-orbital coupling (155.37 cm⁻¹) and intersystem crossing probabilities in spin-forbidden region causes the electron to spin flip at the minimum energy crossing point and access to the lower singlet PES. Nonadiabatic rate constant k is estimated to be quite rapid, so transition state (¹TS1) is rate-controlled steps. In addition, the electronic structure of oxygen-atom transfer process is further analyzed by localized molecular orbital and Mayer bond order. The analysis finds that the form of main bonding orbital is the electron contribution from the p(O) in CO₂ to the empty d(Re) orbital.     

Facile synthesis of palladium nanoparticles supported on urea-based porous organic polymers and its catalytic properties in Suzuki-Miyaura coupling

By using urea linked porous organic polymers as template, a new nano palladium catalyst with low Pd loading can be easily prepared (1.0 wt% Pd only). Although such less amount of Pd was contained in this new catalyst, it is still an effective catalyst for the Suzuki-Miyaura coupling of aryl iodines and aryl boric acids, affording biphenyl products in excellent yields with outstandingly enhanced turnover numbers (up to 10,536) under green solvent (water).     

On the Role of Symmetry in Vibrational Strong Coupling: The Case of Charge‐Transfer Complexation

It is well known that symmetry plays a key role in chemical reactivity. Here we explore its role in vibrational strong coupling (VSC) for a charge‐transfer (CT) complexation reaction. By studying the trimethylated‐benzene–I₂ CT complex, we find that VSC induces large changes in the equilibrium constant K_DA of the CT complex, reflecting modifications in the ΔG° value of the reaction. Furthermore, by tuning the microfluidic cavity modes to the different IR vibrations of the trimethylated benzene, ΔG° either increases or decreases depending only on the symmetry of the normal mode that is coupled. This result reveals the critical role of symmetry in VSC and, in turn, provides an explanation for why the magnitude of chemical changes induced by VSC are much greater than the Rabi splitting, that is, the energy perturbation caused by VSC. These findings further confirm that VSC is powerful and versatile tool for the molecular sciences.     

Molecular dynamics in a miscible polyester blend

The dynamic mechanical and dielectric spectra of a miscible polyester and polycarbonate blend are investigated with emphasis on the latter technique. It was found that relaxation spectra for the blends from both techniques are broader than those of the constituent homopolymers. This is ascribed to greater intermolecular coupling and concentration fluctuations within the blends. The composition at which the greatest coupling occurs is dependent on the relaxation technique used and is skewed towards the component which shows the highest degree of intermolecular coupling. A number of parameters, such as relaxation time of the polymer molecules in the blend and relaxation strength, are compared as a function of reduced temperature (experimental temperature scaled by the glass transition temperature). Whereas blend behavior is generally intermediate between that of the homopolymers, it appears as though mobility of compositions with low polyester content have a greater relaxation time and possess a higher activation energy when compared to a simple, weighted average of the corresponding homopolymer values. © 1996 John Wiley & Sons, Inc.     

Total integrated reflection loss in a laser diode to single-mode fibre coupling system

A geometrical optics approach is used to analyse the reflection of a divergent beam falling onto a concave or convex surface. The polarisation state of a ray in the incident beam depends on the position where the ray impinges upon the surface. The distribution of transmittance over the surface for different polarisation states is determined. An integration of the transmittance distribution determines the total reflection loss of a coupling lens used in a laser diode to single-mode fibre coupling system.     

一种新型毫米波微带均衡器的设计与实现

分析了平面回音壁模介质谐振器的特点及其与微带线耦合产生均衡的原理,并在此基础上给出了一种新型的毫米波均衡器子结构.仿真分析证明,这种结构具有良好的Q值和耦合度可调性.最后,用此子结构级联设计出新型毫米波均衡器,并且呈现良好的特性.     

光栅选线TEA CO2激光快速调谐技术研究

已研制了一种新型的采用直驱交流伺服电机的光栅选线TEA CO2激光器快速调谐系统,介绍了该系统的构建和设计,包括激光器快速调谐系统的硬件构成、软件设计及系统的运行流程,并进行了初步的实验研究。     

自由空间光通讯中应用的光纤耦合系统设计

在分析光纤通信、光纤传感等系统光纤耦合特点的基础上,讨论了自由空间光通讯系统光纤耦合前端的设计理念和总体要求。给出了针对840m通讯波段的光纤耦合系统设计实例,并且对设计优化结果进行了分析。