Thermodynamic and structural study of metal complexes of organic ligands containing conjugated heterocycles.

GABRIELA A. IBAÑEZ; GABRIELA LEDESMA,; GRACIELA M. ESCANDAR; ALEJANDRO C. OLIVIERI

Santiago de Chile

Congreso; XXXII International Conference on Coordination Chemistry; 1997

The interaction of organic compounds containing enolazo/ketohydrazo and enolimine/ketoenamine functional groups with transition metal ions is studied. The ligands investigated are alfa-derivatives of phenol, 2-naphthol and 9-phenanthrol, all capable of suffering prototropic tautomerism. The existence of proton transfer both in the ground and excited states of the free ligands   was established   using   spectroscopic   techniques and semiempirical MO calculations (AM1 for the ground and INDO/S for the excited states), in order to know their tautomeric behaviors. Both the ligands acidity and the complexes   stability constants   were determined by potentiometric and spectrophotometric techniques. In all cases, metal /ligand 1:1 and 1:2 ratios were evaluated (in the case of a binucleating ligand a 2: 1 ratio was also studied).  The possible structures of the complexes were postulated, and the likely coordination ´sites were established.