Charge transport,injection, and photovoltaic phenomena in oligo(phenylenevinylene) based diodes

We report on the charge transport and injection phenomena of (E,E,E,E)‐1,4‐bis[(4‐styryl)styryl]‐2‐methoxy‐5‐(2′‐ethylhexoxy)benzene (MEH‐OPV5) sandwiched between asymmetric contacts. The hole mobility of MEH‐OPV5 was determined by means of transient electroluminescence. The steady‐state current was injection‐limited. The electric field and temperature dependence of the current were quantitatively described by a phenomenological injection model of thermally assisted charge‐carrier tunneling in a one‐dimensional chain of hopping sites. Furthermore, we report on the photovoltaic properties of thin‐film photovoltaic cells on the basis of donor–acceptor heterojunctions. MEH‐OPV5 and buckminster fullerene were used as the donor and acceptor materials, respectively. The emphasis was on the role of morphology in such devices. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2665–2673, 2003     

Synthesis of valsartan via decarboxylative biaryl coupling

An efficient synthesis of the angiotensin II inhibitor valsartan (Diovan) is presented. Two routes were evaluated, both making use of an advanced version of our decarboxylative coupling for the construction of the biaryl moiety. Thus, in the presence of a catalyst system consisting of copper(II) oxide, 1,10-phenanthroline, and palladium(II) bromide, 2-cyanocarboxylic acid was coupled with 1-bromo(4-dimethoxymethyl)benzene in 80% yield and with 4-bromotoluene in 71% yield. The valsartan synthesis using 1-bromo(4-dimethoxymethyl)benzene was completed in four steps overall with a total yield of 39%, via a novel route that presents substantial economical and ecological advantages over the literature process, as it is more concise and stoichiometric amounts of expensive organometallic reagents are avoided.     

Reaction kinetics and magnetic properties of Ba and Sr ferrites

This Mössbauer study is concerned with the formation mechanism of hexaferrites (n=6) and of monoferrites (n=1) in the systems (1) BaCO₃+nFe₂O₃, (2) SrCO₃+nFe₂O₃ and (3) 0.5BaCO₃+0.5SrCO₃+nFe₂O₃. With a molar ratio of 1∶1 for the starting materials one gets final reaction products with different crystalline structures. The experimental results indicate that the thermodynamical final state of the hexaferrite formation is reached on different routes. Various reaction models are discussed.     

On the determination of the column dead volume from homologous series

Summary The calculation of the column dead volume from high precision gross retention times of the n-alkanes pentane to heptadecane in an ODS/MeOH system yields values showing an apparently linear decrease with increasing carbon number. This effect is thought to be related to the partial exclusion from pores. If retention data are corrected for exclusion, one uniform dead volume is obtained.     

57Fe and119Sn Mössbauer investigations on some substituted barium hexaferrites

⁵⁷Fe and¹¹⁹Sn Mössbauer measurements have been carried out on powder samples of three differently substituted M-type barium hexaferrites. By⁵⁷Fe Mössbauer measurements in an external magnetic field applied parallel to the -ray direction, we found a canted spin structure for all samples. Furthermore, we detected a strong preference of the Sn⁴⁺ ions for the 4f₂ sites. From⁵⁷Fe Mössbauer measurements aboveT _N, we conclude that the substitution does not influence the 2b sites. The analysis of the magnetically split¹¹⁹Sn Mössbauer spectra at room temperature in the case of the Co-Sn and Zn-Sn substituted samples shows a strong difference between the two. The spectra were interpreted due to the different surroundings of the Sn⁴⁺ ions.