Structures of (Z)-N,N′-bis[1-pyridin-2-yl-meth-(E)-ylidene]oct-4-ene-2,6-diyne-1,8-diamine (PyED) before and after complexation with Mg2+ (Mg2+-PyED), and (Z)-N,N′-bis[1-pyridin-2-yl-meth-(E)-ylidene]oct-4-ene-2,6-diyne-1,8-diamineplatinum(II) hexafluorophosphate (Pt-PyED). A. PyED; B. Mg2+-PyED; C. Pt-PyED. See Materials and Methods for syntheses of compounds. The metallation of PyED, a bis(pyridine)enediyne ligand, with Mg2+ occurs when it forms a Mg(II) complex upon dilution in cell culture medium (8,14).