The Circular Dichroism and Magnetic Circular Dichroism Spectra of Bis(stilbenediamine) nickel(II) Complexes

Abstract
The temperature dependence of the absorption and circular dichroism spectra for [Ni((+)-stien)2](ClO4)2 is indicative of the equilibrium between the square planar (yellow) and tetragonal (violet) species in acetone solutions. On the other hand, the square planar species is predominant in a methanol solution, even at room temperature, in the case of [Ni(meso-stien)2](ClO4)2. The Cl− as a counter anion favored an equilibrium slightly displaced to the tetragonal species. The analysis of the CD and MCD bands suggests an ordering of the d-orbital energy levels of dx2–y2>>dz2>dxz,dyz>dxy.