New azo-azomethine dyes, L1–L3, with N2S2O2 donor set of atoms have been synthesized via condensation reaction of 1,2-bis(2-aminophenylthio)ethane with 5-(4-X-phenyl)-azo-salicylaldehyde (X = Cl, OMe and Me). The new dyes were characterized by IR, UV–Vis, 1H NMR and fluorescence spectroscopy as well as mass spectrometry and elemental analysis. Mononuclear nickel(II) complexes of the dyes have been also prepared. The crystal structure of [NiL1]·0.5H2O was determined by single-crystal X-ray diffraction. The thermal analysis data indicate that all prepared dyes, L1–L3, are thermally stable up to 320 °C. The fluorescence behavior of the prepared complexes have been also investigated and compared to those of L1–L3.
