Spectroscopic studies, lead halides

Our latest results in this field stem from a matrix-spectroscopic study of the isomerization of nitrosyl halides (152) and isonitrosyl halides (153).201 Irradiation of nitrosyl bromide (152 X = Br) and nitrosyl chloride (152 X = Cl) leads to the corresponding isomers isonitrosyl bromide (153 X = Br) and isonitrosyl chloride (153 X = Cl). Both compounds, NOBr and NOC1,202 have again been identified by comparison of the experimental and calculated (BLYP/6-311+G ) IR spectra. The back-reactions 153 - 152 can be initiated by UV, visible or IR light. Astonishingly, this retransformation also occurs spontaneously even in the matrix at 10 K under exclusion of any UV/VIS or IR radiation. 

While many spectroscopic studies have been published on dimers, the most extensive polymer studies have been with Ag, Na, and Cu clusters. As might be expected much of the interest in silver relates to the photographic process where it appears that a four-atom silver cluster on a silver halide surface leads to reduction by developer, whereas a three-atom cluster does not. The electron spin resonance (ESR) spectrum of sodium in argon confirms that the trimer is covalently bonded and not an equilateral triangle. Ultraviolet photoelectron spectroscopy (UPS) of Cu clusters indicates that the d band is separate from the s band, unlike in the bulk or in the Xa calculations mentioned earlier. 

This article describes the solid state polymerization of 1,i-disubstituted butadiene derivatives in perovskite-type layer structures, in layered structures of organic ammonium halide salts, and in lipid layer structures. Recent investigations by spectroscopic methods and x-ray structure analyses are described. The studies clearly indicate that the photolysis in the crystalline state leads to the formation of 1,i-trans-polymers exclusively. Crystal structure analyses of monomeric and polymeric layer perovskites demonstrate that upon y-irradiation a stereoregular polymer is obtained in a lattice controlled polymerization. 

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