Five novel azo-azomethine ligands with NN'OS coordination spheres were prepared by reaction of methyl-2-{N-(2′-aminoethane)}-amino-1-cyclopentenedithiocarboxylate (Hcden) with (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde and its substituted derivatives and then the corresponding nickel (II) complexes were synthesized. The structures of ligands and the complexes were characterized by elemental analyses, IR, UV–Vis, 1H ...