Chelation of ThIV, EuIII and NdIII by dianionic N,N′-bis(pyridoxylideneiminato)ethylene, (Pyr2en)2-.: On the search of feasible modelings for heavy metals damage inhibition in living beings

The neutral Schiff base N,N'-bis(pyridoxylideneiminato)ethylene {H(2)pyr(2)en} reacts with Th(NO3)(4)center dot 4H(2)O, NdCl3 center dot 6H(2)O and EuCl3 center dot 6H(2)O to give [Th(pyr(2)en)(2)(H2O)] (1), [Nd(pyr(2)en)(Hpyr(2)en)]center dot 12H(2)O (2) and [Eu(pyr(2)en)(Hpyr(2)en)] (3). In the three not yet reported bimolecular chelate systems the endo hydroxyl groups of the rings undergo deprotonation confirming the remarkable ability of the pyridoxal-containing ligand H(2)pyr(2)en to yield stable heavy metal chelates with unusual coordination polyhedra. Complexes 2 and 3 show a coordination number 8 for Nd and Eu, achieving a distorted quadratic antiprism. In complex 1 the additional water molecule increases the coordination number of Th to 9 producing a capped square antiprism. The synthesis and structural elucidation of the title complexes starting from a probably non-toxic metabolite like H(2)pyr(2)en should represent a useful contribution to the research on models of prevention and therapy of damage caused by radioactive and heavy elements. (c) 2007 Elsevier Inc. All rights reserved.