Abstract
This thesis describes the preparation of iron(II) complexes of a variety of amino-acids and similar ligands, such as pyridine-2-carboxylic acid and and pyridine-3-carboxylie acid. All the compounds were extremely sensitive to aerial oxidation, and for this reason all the preparations were carried out under an atmosphere of nitrogen, and subsequently, all the instrumental techniques were carried out on the dry complexes handled either under nitrogen or in vacuo, All the products are 2:1 amino-acid:iron complexes with the exception of the dicarboxylic amino-acids, aspartic and glutamic acids, and the sulphur-containing acid, cystine, which all formed 1:1 complexes. Magnetic measurements and reflectance spectra indicate that in all cases the iron possesses a higher-spin d6 electronic configuration, the ligand environment being distorted octahedral. All the complexes were magnetically normal, with the exception of bis(glycylglycinato) iron(II) and the complexes of the sulphur-containing amino-acids, cysteine, cystine, S-methyl cysteine and methionine. All these showed the presence of some antiferromagnetic interactions within the complex, due, probably, to the predominantly polymeric nature of the structure. Reaction of these complexes with nitric oxide gave rise to a variety of products, rather than the expected nitrosyl complex. Nitrosyl complexes were obtained with bis(glycinato) iron(II), bis(trypto-phanato) iron(lI), bis(serinato) iron(II), bis(histid-nato) iron(II) and from a solution of cysteine and iron(II) sulphate heptahydrate. The product of the latter reaction is thought to be cystinatoiron dinitrosyl. When iron(II) complexes of the other amino-acids were reacted with nitric oxide in a similar manner, a variety of uncharachterizable, and sometimes unstable, iron(III) products was obtained. Initial studies of the reaction between iron(II) sulphate, cysteine and sodium nitrite were carried out at elevated temperature. Although no definite conclusions can be made concerning the nature of the reaction, it would appear that the complex(es) formed in the reaction are not as simple as those suggested by van Roon. Initial investigations were also carried out into the study of iron(II) amino-acid complexes in solution by the use of NMR spectrometry. This would permit study of the metal complexes in very dilute solutions by the measurement of the magnetic susceptibilities of the complexes, and by measurement of the shift of signals on the addition of iron(II), information can be gained concerning the binding sites in the complexes.