Structural Study of the Complex of Al(III) with 1,2,-Benezenediol. Solvent Effects

M.I. SANCHO; A.H. JUBERT; S.E. BLANCO; F.H. FERRETTI; E.A. CASTRO

Global J. Mol. Sci.

Año: 2006 vol. 1 p. 33 - 41

Abstract: The stability of the complex formed by two molecules of 1,2-dihydroxybenzene and one molecule of AlCl3 in solutions with different permittivity and temperature was investigated by means of the B3LYP/6-31G (d) method and using the IPCM model. It was assumed that the formation of the complex takes place by simple reactions between ions of opposite charges. It was also proposed an equation that explains the changes of the complexation equilibrium constant with the permittivity of the reaction medium. The calculations performed allowed to prove that the increase of the hydrogen-bond donor ability of the solvents favor a higher thermodynamic stability of the reactants with respect to the complex and therefore a decrease of the corresponding equilibrium constants. The non-planar structure proposed for the complex is coherent with the small batochromic shift experimentally observed. In the complex molecule the planes containing the phenyl rings are inclined by 9.2º with respect to the plane that includes the aluminum and oxygen atoms. It was concluded that the formation of the complex is an endothermic process which involves covalent bonds between metal atom and oxygen atoms of catechol and stronger coulombic attractions between the referred atoms and water molecules.