The reaction of both histamine (hista) and cysteine (cys) with aqueous CuCN/S2O32- produced Cu(II) ion. In the histamine case thiocyanate ion was also created leading to the production of Cu(SCN)(2)(hista)(2). With cysteine, the 2-amino-2-thiazoline-4-carboxylic acid (atca) ligand was created leading to the production of Cu(atca)(2)(H2O). The crystal structures of the two complexes are discussed, and pathways for the production of thiocyanate and the atca ligand are proposed.