Mercury Complexes with Tripodal Pseudopeptides Derived from D-Penicillamine Favour a HgS sub(3) Coordination

The pseudopeptides L super(4) and L super(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 beta -methylene hydrogen atoms replaced by larger methyl groups. The two sulfur ligands L super(4) and L super(5) are studied here with the toxic Hg super(II) ion. The formation of the two mononuclear complexes HgL super(4) and HgL super(5) is demonstrated by super(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 sub(3) coordination mode at the expense of the generally preferred HgS sub(2) linear coordination. It appears that the hindered D-Pen pseudopeptide L super(5) is capable of stabilizing the unusual HgS sub(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. Tripodal pseudopeptides anchored on a nitrilotriacetic chemical scaffold and extended with three D-penicillamine units stabilize the unusual HgS sub(3) coordination over a large pH range in a hindered coordination environment.