Chemical effects of the (n, gamma) reaction in some solid complexes of cobalt, rhodium and iridium.
thesisposted on 19.11.2015, 08:45 by Mary E. Gravenor
This research has been concerned with the chemical effects of the (n, gamma) reaction in the following complexes: [m(NH3)5Cl] Cl2, trans [M(NH3)4Cl2] Cl and trans [M(en)2Cl2] Cl where M is cobalt(lll), rhodium(lll) or iridium(111). The work can be divided into two parts, a) the study of the fate of the recoil metal atoms following the (n,gamma) reaction and b) the macroscopic effect caused by neutron-irradiation throughout the solid lattice. The methods which have been employed to study the different aspects were as follows. a) The fate of recoil metal atoms was determined by paper electrophoresis. Several recoil species were observed, in particular for iridium complexes, and the results are explained using the hot-zone model. b) The macroscopic effect was examined by labelling the complexes with chlorine-36, in the complex ion, prior to irradiation, and then noting any changes brought about in the distribution of the isotope as a result of neutron- irradiation. It was found that, provided the time of irradiation was long enough, almost total rupture of metal to ligand chlorine bonds occurred. The extent of the macroscopic effect was confirmed by far infrared spectroscopy and by re-irradiation of an electropherogram of irradiated [Ir(NH3)5Cl] Cl2 after decay of recoil iridium-192 activity. In general, it is found that the order of stability of the complexes to metal-ligand bond rupture appears to be the reverse of that of the complexes in normal chemical reactions. An explanation is suggested for this. In order to explain the large amount of disruption caused on a macroscopic scale, a theory is advanced of interaction of reactive species formed in the recoil zones with defects formed in the solid by the gamma radiation accompanying the thermal neutron flux.