5-Amino-pyrazoles: potent reagents in organic and medicinal synthesis

Molecular Diversity - 5-Amino-pyrazoles have proven to be a class of fascinating and privileged organic tools for the construction of diverse heterocyclic or fused heterocyclic scaffolds. This...     

Rule of five cyclizations in 5‐hexenyl radicals and photocycloadditions of 1,5‐hexadienes: effect of 4‐oxa substitution

The effect of 4‐oxa substitution on the regiochemistry and rate of 5‐hexenyl radical cyclizations was investigated, as a potential model for [2 + 2] photocycloadditions of 2‐acyl‐4‐oxa‐1,5‐hexadienes. Increasing the electron density in the alkene decreases the rate of cyclization in the 4‐oxa‐hexenyl radicals, relative to the all carbon analogs, but has little effect on the regioselectivity of the cyclization. The radical model does not reproduce the high degree of 1,6 closure, observed in the [2 + 2] photocycloadditions for 4‐oxa‐1,5‐hexadiene 1a . However, the radical model does reinforce the interpretation that ground state conformational effects, engendered by substitution remote from the reacting centers have important rate consequences for cyclization reactions. Copyright © 2007 John Wiley & Sons, Ltd.     

Electro-optical characterization of a 2-cyclo-octylamino-5-nitropyridine thin organic crystal film

2-cyclo-octylamino-5-nitropyridine (COANP) single crystals were grown between transparent plates coated with indium tin oxide. The Pockels effect of the crystals was analyzed by an ac modulation method. The figure of merit of electro-optic phase retardation of the COANP crystals is estimated to be 4.2x10(-12) m/V . The crystals were protected by the plates, and the figure of merit of the phase retardation of the crystals did not decrease with time. We believe that the crystal-growth method described is applicable to other organic compounds whose crystal growth from a melt is feasible.     

Growth and characterization of organic nonlinear optical material: 5-Nitroindole (5NI) for optical applications

Single crystals of organic nonlinear optical material 5-Nitroindole (5NI) has been grown by slow cooling solution growth technique using methanol as a solvent. The grown crystal was subjected to single crystal X-ray diffraction technique to determine the lattice parameters. Fourier transform infrared spectrum (FTIR) was recorded to identify the presence of functional groups. The optical properties such as the optical band gap, extinction coefficient (k), refractive index (n) and optical conductivity (σ) were calculated. The optical band gap of 5NI is 2.33 eV. The melting point and thermal stability of the crystal was analyzed from TG/DTA studies. Dielectric studies were carried out at different temperatures and frequencies.     

Cryo-TEM observation of 3-dimensionally ordered aggregates of 5-nm gold particles in organic solvents

In this article, we show evidence for the assembly of ordered 3-dimensional aggregates of 5-nm gold particles in toluene, 1-octanol, n-decane, and chloroform. The use of plunge-freezing allows to freeze the solution containing the aggregates at a rate which does not allow reorganisation of the particles during sample preparation. The samples were then observed using cryo-transmission electron microscopy (cryo-TEM) showing that most of the particles were part of ordered aggregates, thus proving that organisation already exists in solution. In some cases, the stability of the sample under the electron beam made it possible to record several pictures of the same aggregate at different angles and build animated tilt series.     

Solid-supported syntheses of 3-thio-1,2,4-triazoles

Two solid-supported synthesis strategies for the preparation of 3-thio-1,2,4-triazoles are described. In the first, Rink amide resin is combined with Fmoc-protected ω-amino acids, acid hydrazides, and alkyl halides to provide diverse sets of starting materials from which numerous triazoles may be prepared. The second employs t-alkylcarbamateresin (Boc resin) which permits the use of additional pools of starting materials, including isothiocyanates and α- and ω-amino esters, resulting in triazoles with patterns of functional groups that are not possible from the initial route. The combination of multiple resins and resin attachment sites allows the preparation of a diverse library based upon the3-thio-1,2,4-triazole scaffold and avoids the pitfallof having a single linker functionality present at the same position in all library members. General synthetic procedures and representative products from each route are presented. A similarity analysis of representative sublibraries from each synthesis strategy concludes that variation of the solid-phase linker chemistry and attachment site can enhance molecular diversity of the combined triazole library. This revised version was published online in August 2006 with corrections to the Cover Date.     

Industrial applications of sonochemistry in the syntheses of vitamin-building blocks

In this article, the application of ultrasound in syntheses of vitamins and fine chemicals is presented. Based on selected examples, the use of ultrasound in dehydration, isomerisation, and decarboxylation reactions is described.     

Tools for microwave-assisted parallel syntheses and combinatorial chemistry

A protocol for transferring conventional reactions to the microwave field explores the effectiveness of parallel syntheses and combination approaches. Applicability to the reaction systems combiCHEM, multiPREP, MMR8 and HPR is defined. Model reactions have been performed in laboratory equipment. Emphasis is placed on similar reaction conditions in the individual vessels and the repeatability of results. Outcomes include esterifications and multi-center reactions exhibiting a great potential for combinatorial chemistry.     

有机层界面对双层有机发光二极管复合效率的影响

建立了双层有机发光二极管中载流子在有机层界面复合的无序跳跃理论模型.由于有机分子材料的空间及能带结构的无序性，采用刚体模型处理有机层界面问题是不恰当的，而采用无序跳跃模型比较合理.复合效率及复合电流由载流子跳跃距离、有机层界面的有效势垒高度及该界面处的电场强度分布所决定：在双层器件ITO/α-NPD/Alq₃/Al中，当所加电压小于19.5V时，复合效率随着载流子跳跃距离的增加而增加，而大于19.5V时，复合效率随着其距离的增加而减少；复合效率随着有机层界面有效势垒高度的增加而增加； 关键词： 有机层界面 双层有机发光二极管 复合效率 有效势垒高度 无序跳跃模型     

Mössbauer investigations of intermolecular interactions of Fe(CO)5 in frozen organic solutions

The Mössbauer spectra of Fe(CO)₅ dissolved in 39 organic solvents were investigated. An influence on the quadrupole split was found only for those solvents containing carbonylic CO, but not for solvents containing another polar group. The change of the quadrupole split means always a reduction and is independent of temperature. The concentration dependence of the additional split indicates that it is caused only by nearest neighbours.—These results give a hint for a specific weak interaction between the carbonylic CO group of Fe(CO)₅ and the solvents. This cannot be a general dipole-dipole interaction because of the missing influence of other polar solvents, so that a weak chemical bond is suggested.     

Solvent-controlled syntheses of Ni12P5 and Ni2P nanocrystals and photocatalytic property comparison

Nickel phosphide nanocrystals with various phases have been successfully synthesized via a simple solvothermal route at 180 °C for 16 h, employing nickel chloride and white phosphorus (WP) as starting reactants in the presence of sodium dodecylbenzene sulfonate (SDBS). X-ray powder diffraction (XRD) research showed that the pure Ni₁₂P₅ phase with a high yield could be obtained in an ethanol solution, and the pure Ni₂P form was prepared in a mixed system with the volume ratio of water/ethanol of 10:10. Namely, the presence of water molecules induced the phase conversion of nickel phosphides. Furthermore, in order to investigate the correlation between properties and phases, as a case, the photocatalytic degradation abilities of two nickel phosphide phases for organic dyes were compared.     

有机电致发光研究与应用进展

在十多年的时间里，有机电致发光的研究和应用取得了长足的进展．有机电致发光器件具有许多优点，例如：自发光、视角宽、响应快、发光效率高、温度适应性好、生产工艺简单、驱动电压低、能耗低、成本低等．因此有机电致发光器件极有可能成为下一代的平板显示终端．文章介绍了最近几年这方面的研究及应用的进展．     

Progress in organic spintronics

Recent progress in organic spintronics is given an informative overview, covering spin injection, detection, and trans-port in organic spin valve devices, and the magnetic field effect in organic semiconductors （OSCs）. In particular, we focus on our own recent work in spin injection and the organic magnetic field effect （OMFE）.     

Ultrasound in organic electrosynthesis

Mechanical effects induced by ultrasonication can be very helpful for the activation of electrochemical reactions. The continuous cleaning of the electrodes by ultrasound irradiation of the electrochemical cell or the enhancement of mass transfer at the electrodes are examples of such activation. Finally, ultrasonication can play an important part for the orientation of reactions whose selectivities are very sensitive to stirring. Two very different examples have been chosen to illustrate these phenomena: the indirect electrooxidation of di-ketone-L-sorbose into the corresponding ketogulonic acid and the direct electroreduction of acetophenone into pinacol.     

Excitons in organic semiconductors

In this article, excitonic effects in organic semiconductors investigated within the framework of many-body perturbation theory are reviewed. As an example for this technologically relevant class of materials the oligoacene series is studied. The electron–hole interaction is included by solving the Bethe–Salpeter equation for the electron–hole Green's function. This approach allows for the evaluation of the exciton binding energies, which are of major interest concerning the application in organic opto-electronic devices. We start the discussion with a comparison of the Kohn–Sham band structure with recent angular resolved photo-emission data. Starting from this one-electron band structure we focus on the impact of the electron–hole interactions on the optical properties by solving the Bethe–Salpeter equation. We demonstrate the dependence of the exciton binding energy on the molecular size and emphasize the effect of the intermolecular interaction on the exciton binding energies by means of pressure investigations. To cite this article: P. Puschnig, C. Ambrosch-Draxl, C. R. Physique 10 (2009).     

有机层厚度变化的有机电致发光器件与微腔器件光谱分析

设计中心波长为520nm,改变有机层厚度,即空穴传输层NPB和发光层Alq3的厚度,分别由10nm逐渐增加至100nm,器件的总体厚度也随着改变,分别计算模拟出有机电致发光器件(OLED)和微腔有机电致发光器件(MOLED)的电致发光谱(EL),并对光谱的积分强度、峰值强度、半峰全宽、峰值位置的三维分布图进行比较分析。综合考虑光谱的峰值位置(中心波长)、最大的峰值强度和积分强度(与亮度、效率相关)、最小半峰全宽(色纯度高)进行合理的设计,可以找到最佳厚度。发现:NPB和Alq3的厚度分别为70和62nm时,器件性能最佳,并且微腔器件的结果尤为明显。结果表明,通过模拟计算,可以深入探索MOLED和OLED发光特性,设计出合理的器件结构。