Studies of some Schiff's base-transition metal complexes.

This thesis describes the preparation and investigation of a number of Schiff's base-transition metal complexes and their reaction with nitric oxide, Throughout this work the aims kept in view have been (a) to obtain in a pure state air sensitive compounds, (b) to characterise the compounds using available physical techniques, and (c) to correlate their properties by means of current chemical theories and to emphasise similarities between these and related but established compounds. The metals investigated are Mn(II), Fe(II), Co(II), Ni(II) and Cu(II). The Schiff's bases are bis(salicylaldehyde)-ethylenediimine (Fig. 1(a)) and many of its derivatives. The cobalt compounds are oxygen carriers but their reaction with nitric oxide has been found irreversible. Eleven new five co-ordinate covalent nitrosyls of Co(I) have been isolated presumably possessing a tetragonal pyramidal structure. All have fractional magnetic moments (~ 0,6 Bohr Magnetons) and from magnetic studies over a temperature range 90°-300°K have been shown to exhibit temperature independent paramagnetism. Variations in the nitric oxide infra-red stretching frequency in this series of nitrosyls have been related to changes in the amount of double bond character in the cobalt-nitric oxide bond consequent upon electron withdrawal from or release to, the metal by substituents in the benzene rings. This is believed to be one of the first 'inorganic' series in which such substituent effects have been studied. Bis(salicylaldehyde)-ethylenediimineMn(II) and Fe(II) have been prepared, the latter for the first time in a pure state. These compounds reacted with nitric oxide but those of Ni(II) and Cu(II) did not. It has been reported that bis(salicylaidehyde)-ethylenediimine Co(II) contains a bridging water molecule. This has not been confirmed