Synthesis, characterization, and sorption activity of novel azo-colorants derived from phloroglucinol and antipyrine and their metal complexes

Abstract

Two novel azo-colorants derived from phloroglucinol and antipyrine as well as 10 metal complexes with Co(II), Ni(II), Zn(II), Cu(II), and Cd(II) were isolated and studied by a set of methods (¹H, ¹³C NMR, IR, UV-VIS, EPR, X-ray structure determination). The azo-coupling of phloroglucinol with a 5-pyrazolone amino-derivative led to the isolation of a colorant H₃L¹ which was presented in the hydroxy-azo tautomeric form. At nitrosation of H₃L¹, the product H₃L² was isolated, which can be described as tri-oxo di-hydroxylamino hydrazone. According to the X-ray structure determination, the Cd-complex of H₃L¹ exhibited the dimeric form with two unionized organic ligands in the inner sphere. It was also found that chloride anions bridge two cadmium cations to form dimers. According to EPR spectra, the Cu-complex with H₃L¹ exhibited distorted tetragonal symmetry associated with the d_x²−y² ground state rather than d_z², and the corresponding Cu–H₃L² complex was described by a cubic symmetry of the coordination medium. Both H₃L¹, H₃L², and their metal complexes show coloristic activity towards wool, polyamide, and polyacetate fibers, which are strongly resistant towards UV-irradiation. The H₃L² compound possessed good sorption activity towards heavy metal cations from aqueous solutions of trace concentrations both under static and dynamic conditions.