Metal ion – biomolecule interactions. IV. Methylmercury(II) complexes of l-methylimidazoline-2-thione (methimazole), a potentially useful protective agent in organomercurial intoxication

Abstract

Two 1:1 methylmercury(II)-1-methylimidazoline-2-thione (methimazole, MeImSH) complexes, [MeHg(MeImSH)]NO3 and [MeHg(MeImS)], have been isolated from aqueous solution under acidic and basic conditions, respectively. 1H nmr and ir spectroscopy, as well as analytical data, were used to characterize the complexes. The nmr data, in particular, lead to the conclusion that the principal binding mode under both sets of conditions involves the sulfur atom at C2. However, under conditions of 2:1 (MeHgII:MeImSH) stoichiometry, binding to N3 is also found to occur. These interpretations have necessitated a reexamination of the 1H nmr spectrum of the free ligand, in particular with respect to assignment of NH and SH resonances corresponding to the two possible tautomeric forms. It has been found in this work that 1-methylimidazoline-2-thione shows a high affinity for MeHgII binding, which may be pertinent with respect to a previous report concerning the protective nature of this compound in organomercurial intoxication.