Synthesis and polyester printing applications of transition metal complexes of tridentate 5-(m-tolyldiazenyl)salicylaldehyde thiosemicarbazone derivatives

Thiosemicarbazone metal complexes are intriguing molecules with a variety of applications in several fields, including the pharmaceutical sector, analytical chemistry, and textile industries. Here, we designed and synthesized 12 transition metal complexes based on thiosemicarbazone as a tridendate group and azo moiety as a chromophore part, in addition to evaluating their color strength and fastness properties. The tridentate ligand derivatives of 5-(m-tolyldiazenyl)salicylaldehyde thiosemicarbazone reacted with four transition metal salts (copper, cobalt, nickel, and iron salts) in refluxing alkaline ethanol to afford the corresponding thiosemicarbazone complexes. The ligands behaved as double-deprotonated tridentate ligands that connected to the transition metal ions through the deprotonation of phenolic-OH and thiol-SH, as well as the azomethine nitrogen atom, to generate fused five- and six-membered heterocycle rings. The obtained metal complexes were characterized by elemental analyses, atomic absorption, IR, and UV–Vis spectra. The color strength and fastness properties of the printed fabrics were tested, showing good to excellent properties.