Hydrogen-1 and carbon-13 nuclear magnetic resonance studies of gold (I) thiomalate ('Myocrisin') in aqueous solution: Dependence of the solution structure on pH and ionic strength

The conformation of thiomalate (mercaptosuccinate) in neutral aqueous solutions of the anti-arthritic drug aurothiomalate has been determined by analysis of ¹H-¹H and ¹H-¹³C three-bond n.m.r. coupling constants. The results indicate the formation of a low molecular weight polymer with only sulphur co-ordination for Au^I. At high ionic strength additional ¹H and ¹³C n.m.r. resonances appear and peaks broaden, consistent with the formation of higher molecular weight species with up to three different environments for thiomalate. Structural changes are accompanied by a new electronic absorption band at 340 nm. High molecular weight polymers are also formed at low pH, where the ¹H and ¹³C resonances are severely broadened.