Gerhard Resch

Lecture notes on solution chemistry

Fundamental considerations the extended donor - acceptor approach influence of solvent properties on solute properties differentiation of liquid water influence of solute properties on solution properties the concept of supramoleuclar system organization concluding remarks.

Fragen der molekularen Systemorganisation, II. Solvatochrome Komplexe

Several mixed complexes, such as Fe(phen)2(CN)2 are subject to variations in color, according to the acceptor properties of the molecular environment. The charge transfer band is gradually shifted to decreasing wave length of the absorption maximum, as the acceptor number of the solution is increased. Likewise, the charge transfer band of the copper(II)-complex with tetramethyl-ethylenediamine and acetylacetonate as ligands is shifted to greater wave length as the donor number of the solution is increased, thus providing evidence for gradual changes from the planar into octahedral arrangement. All complexes have in common that their coordination centre is hard enough to respond to changes of an essentially hard environment and soft enough to redistribute any changes in charge density over the whole system in such ways that the basic characteristics of the complex molecule under consideration is retained. The charge density pattern around the coordination centre, which is at the same time an integral part of the molecular outer regions, appears to retain locally a nearly invariant charge density. The redistribution of the charge density pattern appears to be subject to the regulating actions around the coordination centre. This is therefore considered as representing the highest hierarchic level, to which the charge densities in all other boundary areas are subordinated. Reorganization of the charge density pattern is performed due to the mobilities of the π-electron systems under control of the said superordinated levels. The lowest hierarchic level seems to be represented by the charge density areas along the structural framework, which provides the static boundary conditions for the more highly developed dynamic properties of the higher levels.

Fragen der molekularen Systemorganisation — I Eisen-Phenantrolin-Komplexe

The rationalization of the properties of iron-phenantroline complexes has lead to their description in terms of Molecular System Organizations. In tris(phenantroline)iron complexes the coordination centre and its immediate environment, i.e. the FeN6 group is highly symmetrical and found nearly invariant towards changes in oxidation number, in substitution and in molecular environment. Its decisive regulating functions suggest its operation as the highest hierarchic level of the system. Subordinated to this hierarchic level appear the peripheric charge density regions of the complex ion, which are responsible for flexible adaptation of the system to its environment. The actions of this level are supported by the high flexibility of the π-electron system of the ligands and by the structural framework, both of which are considered to provide the lowest level.As long as the highest level can provide for the invariance of the symmetrical framework of the FeN6 group, the complex is maintained in a low spin state. Distortion of the symmetry of the FeN6 group, as for example effectuated by a substituent in 2-position leads to an increase in dynamic properties and to the establishment of the high spin state, which is found also in bis(phenantroline)iron complexes (with less symmetrically arranged central regions). It is emphasized that anLS →HS transition involves passage of a state of high dynamic order. It is suggested to useArrhenius plots of the rate coefficients of homologous reactions as a measure of the system organization, which appears to be improved as thek-values are approaching those evaluated for the isokinetic temperature. It is finally emphasized that it is principally impossible to acquire full and precise knowledge of the molecular organization of a real system. The limited knowledge accessible may, however, lead to new aspects both in materials science and in biochemical aspects of biological systems.

Thermisch stimulierte Lumineszenzerscheinungen II: Einfluß der Vorbehandlung auf das Verhalten verschiedener Metallpulver

Thermoluminescence of metals is not expected on ground of the theory. The effects which have been found for Cu, Fe, Cr, Zn, W and Mo might be regarded as due to the formation of oxygen containing superstructures with semiconducting properties in the surface regions. Both the emitted thermoluminescence energy and the temperature at which its peak in the glow curve is found for Cu and Mo, are influenced by the mode of the pretreatment of the sample. The values are found lower after previous cooling and higher after previous grinding or heating in a vacuum. For all metals under investigation the phenomenon of the so-called “contact-memory” has been found. The effects of thermal or mechanical pretreatment of the metal powders are also reflected in corresponding changes in adsorption behaviour. The results allow certain conclusions about the energy distribution over the various hierarchic levels.

Mechano-elektrochemische Effekte, VI. Einfluß der Elektrodengeometrie auf Potentialverschiebungen bei der plastischen Deformation von Kupfer und Hinweise auf die Systemorganisationen

SummaryPlastic deformation of a copper electrode in an aqueous 10−4M Cu(ClO4)2 solution leads to greater potential shifts, to smaller “post strain effects” and to greater relaxation rates as the ratio interfacial area: volume of copper is increased. It is suggested that its system organization is improved, as the interfacial area is increased. The system organization appears also to be improved as oxidic superstructures are developing at the interface, where the highest hierarchic levels of both electrode and electrolyte are in immediate contact. Further hints as to the system organization of the whole system Cu/CuSO4 solution are obtained from the fact that atpH=2 andcCu + +=10−1 mol/l the redox potential is independent of the pretreatment of the electrode and independent of the presence of oxidic superstructures. It is underlined that the passivity due to the presence of an oxidic superstructure is maintained only atpH >2, whereas at lowerpH-values copper is more readily dissolved. It is suggested that atpH=2 the system is in an optimal state of system organization (OSO), similar to those reported in the course of phase transformations, in extremely thin metal films and in solutions at the isokinetic temperature.