Electrolyte effect on the stereochemistry of copper(II) and nickel(II) polyamine complexes. Thermodynamic considerations

The electronic spectra of some Cu(II) and Ni(II) complexes with the tetradentate polyamines 3,2,3-(tet) (1,5,8,12-tetraazadodecane), trien, (2,3,2-tet) (1,4,8,11-tetraazaundecane), (3,3,3-tet) (1,4,9,13-tetraazatridecane), en, and (tn) (trimethylenediamine) in solns. of different concns. of the inert electrolyte NaClO4 are shown. The change of the compn. of the soln. causes considerable changes in the spectral properties of these complexes: this is ascribed to a variation of the solute-solvent interactions and of the stereochemistry of the chromophore. In Cu(II) complexes, an increase in electrolyte concn. causes in increase in the tetragonal distortion of the complex. In solns. of Ni(II) complexes, a paramagnetic species and a diamagnetic species are present at equil.: an increase in the ionic strength favors markedly the formation of the diamagnetic complex.