A ¹³C NMR study of the interactions of Ag¹³CN and Ag(CN)₂^- with thiomalic acid, L-methionine and DL-selenomethionine

Complexation of Ag⁺ as AgNO₃, solid AgCN and Ag(CN)₂^- by labeled and unlabeled L-methionine, DL-selenomethionine and d,l-thiomalate were studied by nuclear magnetic resonance methods. The ¹³C NMR indicates that only Ag⁺ react with the both L-methionine, DL-selenomethionine at neutral and higher pH via CO₂^- and S or Se atom forming a chelate. The Ag(CN)₂^- and AgCN do not bind to either of these two ligands at any pH. The Ag¹³CN, which is an insoluble polymer, can react with thiomalate to form chelate complexes at neutral pH. Various structures for the chelate formations are proposed.