Iron(III) and nickel(II) complexes of O,N,N,O-chelating benzophenone thiosemicarbazone: Electrochemistry and in situ spectroelectrochemistry

New complexes, [Fe(L)Cl] (1 and 2) and [Ni(L)]·C2H5OH (3 and 4), were synthesized by template condensation of 2,4-dihydroxy-benzophenone-S-methyl-thiosemicarbazone with 5-bromo- and 5-chloro-2-hydroxy-benzaldehyde and characterized by elemental analysis, conductivity measurements, IR, NMR and mass spectra. Complex 4 crystallizes in monoclinic space group P21/c with unit cell dimensions, a = 13.1091 (3) Å, b = 24.2308 (3) Å, c = 15.5808 (4) Å, β = 102.2632 (11)°, V = 4836.22 (18) Å3, Z = 8. The asymmetric unit of 4 contains two main molecules and two ethanol molecules. Electrochemical behaviors of 1–4 were studied using cyclic voltammetry and square wave voltammetry. Voltammetric analysis of the complexes shows a quasi-reversible metal-based reduction processes between −0.55 and −0.78 V followed by an irreversible reduction process within −0.91 and −1.27 V versus SCE. An irreversible oxidation is also observed within −1.10 to −1.23 V versus SCE during anodic potential scans. While the thiosemicarbazone moiety stabilizes +3 and +2 oxidation states for the iron complexes, only NiII is stable in solution with the same ligand in dichloromethane and dimethylsulfoxide. In-situ spectroelectrochemical studies were employed to determine the colors and spectra of electrogenerated species of the complexes.

Four tetradentate N2O2 type complexes of Fe(III) and Ni(II) were synthesized by template reaction. The compounds were characterized by analytical and spectroscopic methods. The electrochemical, in situ spectroelectrochemical and electrocolorimetric studies were employed. The asymmetric unit of 4 contains two main molecules and two ethanol molecules.Figure optionsDownload as PowerPoint slideHighlights
► Tetradentate N2O2 type complexes of Fe(III) and Ni(II) (1–4) were synthesized by template reaction.
► The compounds were characterized by analytical and spectroscopic methods.
► The electrochemical, in situ spectroelectrochemical and electrocolorimetric studies were employed.
► The asymmetric unit of 4 contains two main molecules and two ethanol molecules.