Synthesis and spectroscopic properties of some thermochromic copper(II) complexes ofN(2-aminoethyl) heterocyclic derivatives

Abstract

Compounds of the type CuL2X2, where L =N(2-aminoethyl)piperazine [N(2-amet)pipz],N(2-aminoethyl)-pyrrolidine [N(2-amet)pyrr] andN(2-aminoethyl)morpholine [N(2-amet)morph] and X = BF 4 − , ClO 4 − and NO 3 − , have been prepared and characterized by means of magnetic moments, e.s.r., electronic and i.r. spectra. Only forN(2-amet)pyrr and Cu[N(2-amet)morph]2(NO3)2 complexes, do the electronic and i.r. spectra suggest polyanion coordination. In particular, as their electronic and i.r. spectra in the 293–393K range are temperature-dependent, it may be ascribed to the presence of a reversible continuous thermochromism arising from a temperature-dependent axial interaction between the anion and the CuN4 plane, which diminishes as the temperature increases. In all the other complexes, the thermochromism may be associated with a geometry which is more planar forN(2-amet)morph than forN(2-amet)pipz derivatives.