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Magnetic fields of different strengths can be applied to chemical and biological systems to study processes involving radicals or radical pairs. This work uses two such techniques, electron paramagnetic resonance (EPR) spectroscopy (≥ 150 mT) in addition to time resolved EPR spectroscopy and time resolved infrared (TRIR) spectroscopy (≤ 37 mT). The former are used to monitor metalloproteins, and the photochemistry of phosphorus oxides, while TRIR spectroscopy is used to record the magnetic field effects on the reaction kinetics of neutral radical pairs. The thesis begins with an introduction and an overview of the experimental techniques and developments. This is followed by an EPR study of the Fe(III) binding proteins, transferrin and lactoferrin and the effect thereon of catecholamine stress hormones. Catecholamines mediate bacterial growth by sequestering iron from the iron binding proteins. The mechanism of iron capture is unknown, however, the current work reveals Fe(III) binding by the catecholamine and supports subsequent reduction as the most likely route. Since catecholamines are also administered therapeutically, the validity of EPR as a diagnostic technique is examined and iron loss from human serum transferrin is observed. Also within this work, experiments are presented in which TRIR spectroscopy is used to investigate factors that affect the development of magnetic field effects for radical pairs in different solutions. This initially involves studies on acylphosphine oxides. In addition to the reported photoprocesses, alternative chemistry is uncovered, which occurs when bisacylphosphine oxide is in solutions where the solvent is sufficiently nucleophilic. The photochemistry is investigated using time resolved EPR and density functional theory calculations to suggest three possible structures that are responsible for the additional radicals observed. Furthermore, encapsulated organic radical pairs in reverse micelles are studied. These experiments, in combination with dynamic light scattering measurements provide insight into the magnitude of the observed magnetic field effects and the differing kinetics of the radical pair in the reverse micelles.

Tributyltin hydride (TBTH) has proven to be an extremely useful synthetic reagent which has been widely used for generating free radicals, is largely responsible for the large increase in the use of free radicals in organic synthesis and is the reagent of choice for many researchers. However, the tin residues are highly toxic and difficult to separate from reaction mixtures which precludes the use of tributyltin hydride in the pharmaceutical industry. In this project, triorganogermanium compounds have been investigated as possible alternatives to tin-based radical mediators.

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The reactions of diraethylchloramine with a variety of different substrates has been studied. With basic substrates such as hydrazine and the alkyl substituted hydrazines, dimethylchloramine acts as an oxidising agent, but with ammonia and the methylamines contrast was found with the corresponding NH(_2)Cl reactions. Simple nucleophillic attack of the amine on the diraethylchloramine nitrogen explains the products found in the reactions with CH(_3)NH(_2) and NH(_3), whilst dehydrohalegonation reaction accounts for the observed products. With dimethylamine a complex reaction occurs which is most probably intimately associated with the decomposition of (CH(_3))(_2)NCl itself. Dimethylchloramine reacts in two different ways with methyl esters of certain acids. On the one hand, esters typified by CH(_3)0S0(_2)F, and including CH(_3)0Cl0(_3), yielding a cationic species identified as (CH(_3))(_3)(^+)NCl. In this cation, the nitrogen chlorine bond possesses a slight dipole, the positive end of which is directed towards the chlorine atom, in accord with the (^36)Cl NQR absorption frequency of 56.09 MHz, found in the Cl0(^-)(_4), (CH(_3))(_3)(^+)3NCl Cl0(^-)(_4), being in excess of that found for Cl2 . The application of standard approximate methods to the observed coupling constants for the CIO4 and BP4 indicate that the bonding between the nitrogen and chlorine atoms in the cation involves an almost pure chlorine p orbital. The ion, (CH(_3))(_3)(^+)NCl, is precipitable from aqueous solutions of the chlorine trimethylaraine complex, (CH(_3))(_3)NCl(_2), by Cl0(^-)(_4) and BF(^-)(_4) ions. With the methyl halides, dimethylchloramme reacts to yield, with methyl bromide, the addition complex of trimethylaraine, (CH3)3NBrCl, the infra red spectrum of which fits well with the trends observed for other (CH3)3N (Halogen)2 addition complexes, whilst with methyl iodide, a novel tetramethylammonium pseudopolyhalide, (CH(_3))(_4)(^+)N[(CH(_3))(_2)N(ICl)(_2)](^-), forms. Dimethyl bromamine, (CH(_3))(_2)NBr, reacts in a similar way to (CH(_3))(_2)NCl, with alkylating agents, the unstable (CH(_3))(_3)(^+)NBr 0S02(_)F(^-) forms with CH(_3)0S0(_2)F and (CH(_3))(_2)NBr Cl0(^-)(_4) can be precipitated from aqueous solutions of the fluorosulphate by Cl0(^-)(_4) ions. With CH(_3)I, (CH(_3))(_2)NBr yields, in a similar way to (CH(_3))(_2)NCl, (CH(_3))(_4)(^4)N[(CH(_3))(_2)N(IBr(_2))](^-).