ELECTRICAL-CONDUCTIVITY AND PHASE-TRANSITION STUDIES OF SOME SELECTEDCONGO RED-METAL COMPLEXES

The electrical properties of Congo Red dye (L) and its metal (M) compl exes of M:L molar ratios of 1:1 and 2:1, where M=Cr(III), Fe(III), Cu( II), Zn(II), Zr(IV), Th(IV) and UO2(II), indicated semiconducting beha viour. The activation energies and electrical conductivities depend on the ionic charge of the metal chelates. The activation energies of 1: 1 metal complexes are greater than those of 2:1 metal complexes. The c onductivity data obtained are interpreted on the basis of the molecula r structure of the Congo Red complexes. One phase transition was obtai ned during DTA study of Congo Red dye at 212 degrees C. This phase tra nsition may be due to the rotation of the two naphthalene rings and th e N=N groups around the diphenyl group centre.