Synthesis and characterization of an azo dibenzoic acid Schiff base and its Ni(II), Pb(II), Zn(II) and Cd(II) complexes

The new Schiff base 4,4′-(1E,1′E)-(3,3′-(1E,1′E)-(pyridine-2,6-diylbis(azan-1-yl-1-ylid ene))bis(methan-1-yl-1-ylidene)bis(4-hydroxy-3,1-phenylene))bis(diazene-2,1-diyl)dibenzoic acid (1) was prepared from the condensation reaction of 2,6-diaminopyridine with 4-((3-formyl-4-hydroxyphenyl)diazenyl)benzoic acid in methanol. The compound 1 is potentially an N, O multidentate chelating ligand which could form stable complexes with metal ions in 1:1 up to 1:3 mol ratio of metal to ligand. The 1:1 complexes of Schiff base 1 with Ni(II), Pb(II), Zn(II) and Cd(II) have been synthesized by its condensation reaction with appropriate salts of metal ions. Structures of Schiff base (1) as well as its complexes with abovementioned metal ions were characterized by elemental analysis, mass, IR, UV–vis., 1H and 13С NMR spectroscopy.

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► The azo-azimethene Schif base dye 1 has enol-keto tautomeric.
► The 1:1 complexes of Schiff base 1 with Ni(II), Pb(II), Zn(II) and Cd(II).
► In the complexes a red shift is observed for the π–π* transition.