Abstract
The acid-base properties of 2-(P-substituted benzene-azo)-1, 5-dihydroxynaphthalene have been investigated spectro-photoraetrically. The influence of p-substituents on the ionisation of the O-OH group is discussed. Mesomerically electron repelling substituents prevent ionisation of O-OH by increasing negative centers. Infrared and electronic spectral studies provide proof of the existence of a tautomeric equilibrium between azo and quinone-hydrazone forms in the solid and solution states. Additionally, a number of cobalt(II), nickel(II) and copper(II) complexes of these ligands have been characterized in the solid state. On the basis of elemental analyses, magnetic and spectral data, a distorted octahedral geometry is proposed for all the complexes.