Concerning the thermochromic mechanism of copper(II) and nickel(II) complexes of N,N-diethylethylenediamine

Abstract

The thermochromic mechanism of several Cu(II) and Ni(II) complexes of the type M(dieten)/sub 2/X/sub 2/, where dieten = N,-N-diethylethylenediamine and X = inorganic anion, has not been clearly established. Pressure and thermal studies in the electronic and infrared region (mid-infrared and far-infrared) have been made. In the electronic region, the ''d-d'' transitions shift red with an increase in temperature for both Cu(II) and Ni(II) complexes. With pressure these transitions are toward the red with Cu(II) complexes and toward the blue with Ni(II) complexes. Mid-infrared data are indicative of axial interaction occurring with an increase in temperature and the lack of interaction with pressure increases. Although many factors are involved in determining these differences and anion and steric effects are important, the dominant factor appears to be the distortion of the tetragonal metal atom environment and axial interaction between the anions and the M-N/sub 4/ plane.