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Title: Szilard chalmers studies on some chromium, cobalt and ruthenium complexes.
Authors: Lee, Byung Hun.
Award date: 1972
Presented at: University of Leicester
Abstract: This research has been concerned with the chemical consequences of neutron capture in chromium(III), cobalt(III) and ruthenium(III) ammine complexes: pentammine, ethylenediamine and tetraethylene-pentamine. The isotopic exchange of ligand chlorine atoms of complexed ions with outer anionic chloride ions during neutron bombardment of the solid chromium(III), ruthenium(III) and cobalt(III) ammine complexes has been studied with chlorine-36 labelled chlorine atoms and anionic chloride ions. The order of stability of the complexes is: [M(NH3)5C1]C12<cis- and trans-[M(en)2C12] C1<[M(tetren)C1]C12. Although the retention was increased gradually during prolonged neutron irradiation, which is described as a result of pile annealing (thermal and radiation), a few recoil species were observed on paper electrophoresis. The macroscopic distribution of recoil products in Cr(III) and Ru(III) ammine complexes, determined by the re-irradiation of paper electrophoregram, showed that the rupture of metal-ligand bond is about 2-3% in acid media and about 9-11% in neutral media. The recoil atom reaction was explained using the disorder model, which postulates that the recoil atom generates about its starting point only small changes in the lattice arrangement without producing a melt, and the final fate of the recoil atom is determined by the structure of the immediate environment it has reached after losing its kinetic energy. The chemical effects of internal conversion of outer energetic bromine atoms in Cr(III) ammine complexes (-NM3, ethylenediamine), and 58mCo and 60mCo in the Co (III) tetren complex have been investigated. The experimental observations on isotope exchange and paper electrophoresis indicated that there is no significant evidence for an additional chemical effect. The results were discussed in view of the possibility that the effect of large crystal field stabilization for Cr(III) and Co(III) plays an important role in determining the recoil reactions. Thermal annealing reactions differ from system to system depending on the physical and chemical properties of the host crystal. The isochronal thermal annealing of neutron irradiated [Cr(NH3)5C1] C12 and cis-[Cr(en)2C12] C1 was discussed using the exciton model. Thermal transfer, or exchange, in chlorine-36 labelled [Ir(NH3)5C1] C12 and trans-[Ir(en)2C12] C1 has been shown to give a heating curve similar to that obtained during annealing of neutron irradiated complexes. The substitution of chlorine-36 labelled chlorine atoms in the complex by anionic chloride ions in [Ir(NH3)5C1] C12 was explained by the isotope exchange model, involving a single step chemical exchange. The oscillating isotherm of chlorine-36 labelled trans-[Ir(en)2C12] C1 was explained by a mechanism involving a series of thermal decomposition reaction.
Level: Doctoral
Qualification: Ph.D.
Rights: Copyright © the author. All rights reserved.
Appears in Collections:Theses, Dept. of Chemistry
Leicester Theses

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