Electronic Properties of Biologically Important Molecules

Abstract

The magnetron technique, which had been developed for the measurement of gaseous electron affinities from observations on the equilibrium between atoms electrons and ions at a heated metal surface, was applied to the measurement of electron affinities of some classes of aromatic compounds which show biological activity. The stabilities of a number of anions derived from molecules and radicals were obtained, but it was found that the limitations of the method precluded useful measurements from being made on large polyatomic molecules. Methods were therefore considered which would enable relative electron affinities of these larger molecules to be estimated, and which would also give values for the molecules studied successfully by the magnetron technique. These could then be used as reference values. It has been claimed that an electron capture detector developed for use in gas chromatography could be used to measure electron affinities. After some preliminary experiments to determine the optimum operating conditions of such a detector the compounds which have been previously investigated in the magnetron were introduced into the carrier gas stream flowing through an electron capture detector. The attenuation in electron concentration produced by a known number of acceptor molecules was measured and the results analysed. It was found however that the detector response was proportional to the total collision cross section of the molecules rather than the electron affinity and it was not therefore possible to compare the results from the two methods.12.2 Finally some other methods which have been used to estimate electron affinities were considered. The results obtained by these techniques i.e. charge transfer spectroscopy and polarography, together with some calculated values are discussed and compared with the results obtained in the magnetron.