Mercury Complexes with Tripodal Pseudopeptides Derived from D ‐Penicillamine Favour a HgS 3 Coordination

The pseudopeptides L 4 and L 5 are built on a nitrilotriacetic scaffold and functionalized with three D ‐penicillamine ( D ‐Pen) units. D ‐Pen is an interesting building block and a bulkier analogue of cysteine with the β‐methylene hydrogen atoms replaced by larger methyl groups. The two sulfur ligands L 4 and L 5 are studied here with the toxic Hg II ion. The formation of the two mononuclear complexes Hg L 4 and Hg L 5 is demonstrated by 1 H NMR spectroscopy and mass spectrometry and the tristhiolato coordination is unambiguously evidenced by the UV absorption signatures. An important feature is the stabilization of the HgS 3 coordination mode at the expense of the generally preferred HgS 2 linear coordination. It appears that the hindered D ‐Pen pseudopeptide L 5 is capable of stabilizing the unusual HgS 3 coordination over a large pH range in water, pH > 5.5. This water‐soluble compound can therefore be considered as a promising chelating agent for mercury detoxification.