Synthesis and spectroscopic properties of new azo-dyes and azo-metal complexes derived from barbituric acid and aminoquinoline

Two new azo-dyes, 5-(quinoly-8-azo)pyrimidine-2,4,6-trione (L1) and 5-(quinoly-8-azo)-1,3-dimethylpyrimidine-2,4,6-trione (L2) were prepared by linking 8-aminoquinoline to barbituric acid and 1,3-dimethylbarbituric acid through diazo-coupling reactions. Reaction of new azo-dyes with Cu(II) or Ni(II) salts and unidentated ion gave mononuclear complexes with general stoichiometry [MLX], [M: Ni(II) or Cu(II); X: NO3−, SCN−, CN− or N3−]. On the other hand, two kinds of cobalt(II) complexes with different stoichiometries were prepared. Reaction of azo-dyes with Co(AcO)2 with 2:1 molar ratio gave azo complexes with stoichiometry Co(L)2 while reaction of cobalt salts with tridentate azo-dyes, bidentate ligand, 1,10-phenanthroline (B), and unidentate ion (X: NO3−, SCN−, CN− or N3−), mixed hard–soft donor sets, produced a new set of complexes with general stoichiometry CoLBX. The structures of both azo-dyes and their complexes were identified by elemental analyses, FTIR, 1H NMR, UV–vis, magnetic susceptibility and mass spectral data. The elemental analyses and spectral data indicate that azo-dyes act as monobasic O,N,N′-tridentate ligand. The difference in absorption maximum from ligands to metal complexes was also studied.