A novel hexadentate ligand and its complexes with divalent metal ions (Zinc, Copper, and Cobalt): Synthesis, characterization, and electrochemical investigation

A novel hexadentate ligand, N-(pyridin-2-ylmethyl)-N,N′-(bis-(2-(pyridin-2-ylmethylthio))ethyethanamine) (L), containing “N4S2” donor-set was synthesized. Its reaction with one equivalent of divalent metal perchlorate salts, M(ClO4)2·6H2O (M = Zn, Cu, and Co), in methanol yielded three mononuclear complexes [ML](ClO4)2 (M = Zn, 1; Cu, 2; Co, 3) in octahedral geometry. The complexes were fully characterized and their structures were determined using X-ray single crystal diffraction analysis. UV–Vis spectra of the complexes revealed that metal-to-ligand charge transfer (MLCT) transition bands showed readily red-shift in the trend of Zn(II), Co(II), and Cu(II) complexes. Upon the divalent metal binding, the ligand-based reduction process shifted positively which, otherwise, is not observable in the electrochemical window.

Graphical abstractReaction of a novel hexadentate ligand possessing donor-set “N4S2”, N-(pyridin-2-ylmethyl)-N,N′-(bis-(2-(pyridin-2-ylmethylthio))ethyethanamine) (L), with one equivalent of divalent transition metal salts, M(ClO4)2·6H2O, produced three octahedral complexes, [MIIL](ClO4)2 (M = Zn, 1; Cu, 2; Co, 3).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel hexadentate ligand with “N4S2” donor-set. ► The ligand formed complexes with M(II) (M = Zn, Cu, and Co) in octahedral geometry. ► Upon binding to Zn(II), the reduction potential of the ligand shifted positively.