Abstract:

Equilibria between square planar and pseudo octahedral species of the mixed diamine/β-diketonate Ni(II) complex ([Ni(II)(Me4en)(acac)]ClO4) in four kinds of alcoholic solvents were investigated by means of Vis-spectra. Equilibriumconstants and thermodynamic parameters, which included enthalpy changes (△H) and entropy changes (△S), were evaluated from peak fitting the thermo-solvatochromic Vis-spectra of this complex in the alcoholic solutions. Spectra of the involved square planar and the pseudo octahedral species were also derived from the same analysis. △H data showed that the formation of the pseudo octahedral species was exothermic and the △H values reflect the coordination ability of alcoholic solvents with the central Ni(II) ion. Absolute values of △S relate to the number of liberated alcohol molecules or those coordinated to the central Ni(II) ion. The calculation results are helpful to thoroughly understand the thermochromic behavior of the mixed diamine/β-diketonate ligand Ni(II) complex.

Key words: Thermodynamic parameter, Mixed ligand complex, Thermo-solvatochromism, Vis-spectrum