Abstract
This Thesis aims to increase the understanding of the way in which herbicides inhibit plant photosynthesis by interference at the site of photosystem II. Two structurally dissimilar series of compounds, provided by Schering Agrochemicals (Saffron Walden, U.K.), one rigid, one flexible, both series showing varying herbicidal activity, were submitted to X-ray crystallography, NMR spectroscopy and molecular modelling studies. As a result of these investigations, an explanation is given for the observed trend in activity of both series of compounds. A template for the herbicide binding site is also presented.. The most active molecules in the two series of' compounds were compared using molecular modelling. A model is presented which suggests that both molecules may interact with the same binding site at the photosystem II reaction centre.