Zum Schwingungsverhalten pentakoordinierter Zinn(IV)-organischer Verbindungen. IR- und Raman-Untersuchungen an 2,8,9-Tricarbastannatranen

Summary Results are reported of IR and Raman investigations on four 1-substituted 2,8,9-tricarbastannatranes (1,X=Cl;2,X=Br;3,X=I;4,X=Me). Group-theoretic investigations confirm the trigonal-bipyramidal configuration of the tin atoms. The vibrational frequencies of the coordination (SnN) are correlated to the distancesd (Sn-N). Besides the results on the vibrations of the coordination polyhedrons other results are reported concerning the enantiomerization of the chiral atran skeleton.

     

Photoionisation of ions with synchrotron radiation: from ions in space to atoms in cages

The photon-ion merged-beams technique for the photoionisation of mass/charge selected ionised atoms, molecules and clusters by x-rays from synchrotron radiation sources is introduced. Examples for photoionisation of atomic ions are discussed by going from outer shell ionisation of simple few electron systems to inner shell ionisation of complex many electron ions. Fundamental ionisation mechanisms are elucidated and the importance of the results for applications in astrophysics and plasma physics is pointed out. Finally, the unique capabilities of the photon-ion merged-beams technique for the study of photoabsorption by nanoparticles are demonstrated by the example of endohedral fullerene ions.     

A new strategy to prepare temperature-sensitive poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) microgels

In this study, a new method was developed to prepare temperature-sensitive poly(N-isopropylacrylamide) microgels by free radical precipitation polymerization using siloxane coupling agent as the new crosslinker. Ammonium persulfate acted as the initiator for the radical copolymerization as well as the catalyst for the hydrolysis/condensation of the siloxane groups. The particle diameter and polydispersity of the microgels were measured by photon correlation spectroscopy and the results display that the microgels are monodisperse. The microgels exhibit temperature sensitivity and the phase transition temperature is approximately 31 °C. Furthermore, the diameter of the microgels changes upon heating and cooling processes. These were observed to be reversible. The novel crosslinking method described herein is the condensation of siloxane groups, which is totally different from the traditional double-vinyl crosslinkers. This innovative approach offers an alternative path to prepare functional core–shell particles and inorganic/organic hybrid materials.     

Density functional calculations on cyclodextrins

Conformations of α-, β-, and γ-CDs under anhydrous conditions in the gas phase were investigated by a density functional method, B3LYP/6-31G(d,p). These calculations resulted in several symmetric conformations with different energies. The lowest energy conformations contain two rings of homodromic hydrogen bonds and are referred to “one-gate-closed” conformations. Different orientations of hydrogen bonds lead to four minima. Other conformational minima were found for “open” conformations which correspond to some extent to experimentally determined structures.     

Reversible UV-light-induced ultrahydrophobic-to-ultrahydrophilic transition in an alpha-Fe2O3 nanoflakes film

We describe a simple and robust approach to fabricating an alpha-Fe2O3 switchable surface. The hydrophobicity of alpha-Fe2O3 nanostructures was observed for the first time. A remarkable surface wettability transition can be easily achieved by ultraviolet (UV) illumination. The distinctive properties of surface defects are disclosed by X-ray photoelectron spectroscopy (XPS) analysis. The nanoscale adsorption and photocatalytic properties of Fe2+ defects account for the highly amphiphilic character of the surfaces. We believe that the experiment will further the molecular-scale understanding and manipulation of the wetting behavior on smart devices.