Electron spin resonance studies of chemical systems.

This thesis contains three structural studies of inorganic systems, made by the use of electron spin resonance techniques. They are on dipotassium penta-cyanonltrosylmanganate II, trisodium pentacyanonitrosyl- ferrate I, and solutions of sulphur, enriched with sulphur-33, in 65% oleum. Preliminary studies had already been made on polarographically reduced sodium nitroprusside in form- dimethylamide, and these were extended to 8-irradiated powder, and a 8-irradiated single crystal, of sodium nitroprusside. The results obtained from all these studies concurred, and showed the unpaired electron to be primarily in the dZ2 orbital on iron. This conclusion was confirmed from, observations made on trapped pairs of paramagnetic anions in the irradiated crystal. This was in contrast to the conclusions of Gray and co-workers, who suggested, from their analysis of absorption spectra, that the electron was localised in a ? orbital on the nitrosyl ligand. An E.S.R. study of the dipotassium pentacyanonitrosy1-manganate II (d5) showed that the unpaired electron was primarily in a dxy orbital on the manganese. This conclusion was the same as that reached from work on the isoelectronic chromium complex, by other workers. Solutions of sulphur in 65% oleum are blue, and contain free radicals, uncharged and in low abundance, which slowly decompose to a diamagnetic species. Using sulphur enriched with sulphur-33 in these solutions, it was shown, by E.S.R., that each unpaired electron is located in ?H orbital between two sulphur atoms.