Einen systematischen Gang zur Auffindung und Trennung der h?ufiger vorkommenden S?uren

Ohne Zusammenfassung     

Electron transfer across modular oligo-p-phenylene bridges in Ru(bpy)2(bpy-ph(n)-DQ)4+ (n = 1-5) dyads. Unusual effects of bridge elongation

A series of dyads of general formula Ru(bpy)(2)(bpy-ph(n)-DQ)(4+) (n = 1-5), based on a Ru(II) polypyridine unit as photoexcitable donor, a set of oligo-p-phenylene bridges with 1-5 modular units, and a cyclo-diquaternarized 2,2'-bipyridine (DQ(2+)) as electron acceptor unit, have been synthesized. Their spectroscopic and photophysical properties have been investigated in CH(3)CN and CH(2)Cl(2) by time-resolved emission and absorption spectroscopy in the nanosecond and picosecond time scale. The experimental study has also been complemented with a computational investigation carried out on the whole series of dyads. The absorption spectra of the dyads show new spectroscopic transitions, in addition to those characteristic of the donor, bridge, and acceptor fragments. DFT calculations suggest the assignment of such bands as bridge-to-acceptor (π ph(n)) → (π* DQ) charge-transfer transitions. This assignment is consistent with the solvatochromic and spectroelectrochemical behavior of the new bands. For all the dyads at room temperature in fluid solution, the typical (3)MLCT luminescence of the Ru(II) polypyridine unit is strongly (>90%) quenched, supporting the occurrence of an efficient intramolecular photoinduced electron transfer. The study has revealed, however, that the photophysical mechanism is actually more complex than presumed on the basis of a simple photoinduced electron-transfer scheme. For n = 1, very fast (few picoseconds) photoinduced electron transfer from the MLCT state localized on the substituted bpy ligand to the DQ unit has been observed, followed by slower interligand hopping and charge recombination. For n = 2-5, MLCT excited-state quenching takes place without transient detection of charge-separated product, indicating that charge recombination is faster than charge separation. This behavior can be rationalized in terms of the superexchange couplings expected through this type of bridges for the two processes. The kinetics of MLCT quenching in the dyads with n = 1-5 does not follow the usual exponential falloff with bridge length: after a regular decrease for n = 1-3, the rate constants become almost insensitive to bridge length for n = 3-5. The rationale of this uncommon behavior, as suggested by DFT calculations, lies in a switch in the MLCT quenching mechanism with increasing bridge length, from oxidative quenching by the DQ acceptor to reductive quenching by the bridge.     

The morality of attitudes toward nanotechnology: about God,techno-scientific progress,and interfering with nature

Using survey data, we examine public attitudes toward and awareness of nanotechnology in Germany (N = 750). First, it is shown that a majority of the people are still not familiar with nanotechnology. In addition, diffusion of information about nanotechnology thus far mostly seems to reach men and people with a relative higher educational background. Also, pro-science and technology views are positively related with nanotech familiarity. Results further show that a majority of the people have an indifferent, ambiguous, or non-attitude toward nanotechnology. Multinomial logit analyses further reveal that nanotech familiarity is positively related with people’s attitudes. In addition, it is shown that traditional religiosity is unrelated to attitudes and that individual religiosity is weakly related to nanotechnology attitudes. However, moral covariates other than religiosity seem of major importance. In particular, our results show that more negative views on technological and scientific progress as well as more holistic views about the relation between people and the environment increase the likelihood of having a negative attitude toward nanotechnology.     

Characterization of heat-wave propagation through laser-driven Ti-doped underdense plasma

The propagation of a laser-driven heat-wave into a Ti-doped aerogel target was investigated. The temporal evolution of the electron temperature was derived by means of Ti K-shell X-ray spectroscopy, and compared with two-dimensional radiation hydrodynamic simulations. Reasonable agreement was obtained in the early stage of the heat-wave propagation. In the later phase, laser absorption, the propagation of the heat-wave, and hydrodynamic motion interact in a complex manner, and the plasma is mostly re-heated by collision and stagnation at the target central axis.     

Mechanosynthesis and characterisation of the Li–Sn system

Intermetallic phases Li–Sn were synthesized by ball-milling and characterized for their structures and electrochemical performances. All phases in Li–Sn binary phase diagram were identified by ¹¹⁹Sn Mössbauer spectroscopy, used as reference materials for the study of lithium insertion into tin-based electrode materials. The observed spectra show two distinct environments of tin; the Sn-rich phases and the Li-rich phases. An example of electrochemical properties of these phases is proposed for Li₂₂Sn₅. Irreversibility of the first cycle is related to the structural change (3D→2D) of this phase.     

Synthesis of cis‐3‐methyl‐4‐aminopiperidine Derivatives

A facile approach for the preparation of cis‐3‐methyl‐4‐aminopiperidine derivatives is described. The synthesis was carried out via regioselective ring opening of N‐benzyl‐3‐methyl‐3,4‐epoxi‐piperidine (8), which can be easily obtained in two steps from the corresponding N‐benzyl‐pyridinium salt (5). Seven new cis‐3‐methyl‐4‐amino and amido piperidines compounds were obtained.     

Chemical and electrochemical behavior of metallic technetium in acidic media

The chemical and electrochemical properties of technetium metal were studied in 1–6 M HX and in 1 M NaX (pH 1 and 2.5), X = Cl, NO₃. The chemical dissolution rates of Tc metal were higher in HNO₃ than in HCl (i.e. 8.63 × 10^?5 mol cm^?2 h^?1 in 6 M HNO₃ versus 2.05 × 10^?9 mol cm^?2 h^?1 in 6 M HCl). The electrochemical dissolution rates in HNO₃ and HCl were similar and mainly depended on the electrochemical potential and the acid concentration. The optimum dissolution of Tc metal was obtained in 1 M HNO₃ at 1 V/AgAgCl (1.70 × 10^?3 mol cm^?2 h^?1). The dissolution potentials of Tc metal in nitric acid were in the range of 0.596–0.832 V/AgAgCl. Comparison of Tc behavior with Mo and Ru indicated that in HNO₃, the dissolution rate followed the order: Mo > Tc > Ru, and for dissolution potential the order: E _diss(Ru) > E _diss(Tc) > E _diss(Mo). The corrosion products of Tc metal were analyzed in HCl solution by UV–Visible spectroscopy and showed the presence of TcO₄ ^?. The surface of the electrode was characterized by microscopic techniques; it indicated that Tc metal preferentially corroded at the scratches formed during the polishing and no oxide layer was observed.     

Chemical,Electrochemical, and Structural Properties of Endohedral Metallofullerenes

Ever since the first experimental evidence of the existence of endohedral metallofullerenes (EMFs) was obtained, the search for carbon cages with encapsulated metals and small molecules has become a very active field of research. EMFs exhibit unique electronic and structural features, with potential applications in many fields. Furthermore, functionalized EMFs offer additional potential applications because of their higher solubility and their ease of characterization by X‐ray crystallography and other techniques. Herein we review the general field of EMFs, particularly of functionalized EMFs. We also address their structures and their (electrochemical) properties, as well as applications of these fascinating compounds.     

Existence and Convergence to Equilibrium of a Kinetic Model for Cometary Flows

A kinetic equation with a relaxation time model for wave-particle collisions is considered. Similarly to the BGK-model of gas dynamics, it involves a projection onto the set of equilibrium distributions, nonlinearly dependent on moments of the distribution function. An earlier existence result is extended to bounded domains with reflecting boundaries and to initial conditions permitting vacuum regions. The long time behaviour is investigated. Convergence on compact time intervals (shifted to infinity) to the set of equilibrium solutions is proven. The set of smooth equilibrium solutions is computed.