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Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, were performed for the 1 hydrated platinum(II) and palladium(II) ions and cis-diammineplatinum(II) complex in acidic aqueous solutions. Simplified Density Functional Theory (DFT) calculations were made for the equatorial plane of the platinum complexes. Careful subtraction of solvent spectra allowed a number of 'internal' modes of coordinated H(2)O and NH(3) to be determined as weak residual bands. The [Pt(OH(2))(6)](2+) and [cis-Pt(NH(3))(2)(OH(2))(4)](2+) complexes were found to be six-coordinated with four ligands strongly bound in an equatorial plane. The assignments of the vibrational modes in the equatorial plane could be performed on the basis of the experimental observations and by comparison with metal-ligand vibrations of square-planar complexes, aided by normal coordinate calculations. For the weakly coordinated axial aqua ligands, the low wavenumber range and the polarizibility properties allowed the assignments of the bands at about 365 and 325 cm(-1) to the stretching modes of one short and one longer Pt - O* bound to axial aqua ligands, respectively. A similar picture with even less strongly bound axial water molecules emerges from Raman spectroscopy data for the hydrated palladium(II) ion, [Pd(OH(2))(6)](2+). The results are consistent with a description of the [Pt(OH(2))(6)](2+) and [Pd(OH(2))(6)](2+) aqua ions in C(4v) symmetry, and with the [cis-Pt(NH(3))(2)(OH(2))(4)](2+) complex in the Cs point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements.

The permeable polymer film-formation behavior of a Eudragit RS dispersion was investigated in response to stirring at various rates and for various times in an Ultra Turrax instrument. No additives were used. The minimum film-forming temperature of the liquid, the thermal behavior of the film and the compositions of the dispersion and the foam arising were investigated. It was found that, at a given mixing time, shape-retaining foam formation could be detected at over 17,500 rpm. The polymer was enriched in the foam, while its quantity was decreased in the liquid. The minimum film-forming temperature of the liquid phase did not vary significantly, with the exception of the rate of 24,000 rpm, when a uniform film was not formed because of the bubbles. The glass-transition temperatures of the films formed did not exhibit any differences. Film formation was not influenced by the stirring time at a given rate. It was found that the efficiency of homogenization should not be increased by using a high stirring rate, as a uniform, smooth film did not develop, such a film being indispensable to ensure appropriate drug release. Copyright © 2006 John Wiley & Sons, Ltd.

Twenty-two samples of zinc carboxylates were prepared from saturated, non-cyclic carboxylic acids with systematically altered hydrocarbon chain structures under well-defined conditions. Essential temperature- and solvent-induced changes concerning the coordination of the carboxylate group are shown using selected prepared samples, and general rules for systems containing zinc carboxylates in nonpolar media are presented. It is shown that there are three possible structural forms for zinc carboxylates: polymeric sheet, polymeric chain, and closed tetranuclear oxo complex molecules. These forms are closely related through their physical and chemical transitions. The results show that the spatial structure of the hydrocarbon chain is a crucial factor, besides physical and chemical conditions, limiting the possible forms of zinc carboxylates present in the system. The principles presented enable us to predict and design the behaviour of a system containing zinc carboxylate additives.