Synthesis, Characterization, Cyclic Voltammetry, and Biological Studies of Co(II), Ni(II), and Cu(II) Complexes of a Tridentate Schiff Base, 1-((E)-(2-Mercaptophenylimino) Methyl) Naphthalen-2-ol (H2L1)

Abstract

A novel tridentate Schiff base, 1-((E)-(2-mercaptophenylimino) methyl) naphthalen-2-ol (H2L1), was synthesized by the condensation reaction of 2-hydroxy-1-naphthaldehyde with 2-aminothiophenol in absolute ethanol. The resulting ligand was reacted with Co(II), Ni(II), and Cu(II) ions to obtain tetrahedral CoL1, NiL1, and square planar CuL1 complexes. The Schiff base and its metal complexes were characterized using 1H-NMR, microanalysis, FT-IR, UV-visible, and mass spectroscopy (ESI-MS). All the compounds are soluble in DMSO and DMF. Spectroscopic studies show that the ligand coordinates to the metal center through the azomethine nitrogen, naphthoxide oxygen, and thiophenoxide sulfur to form a tridentate chelate system. Conductance measurements show that these compounds are molecular in solution. Cyclic voltammetry studies show Co(III)/Co(II) and Cu(II)/Cu(I) redox systems to be quasi-reversible involving a monoelectronic transfer while Ni(III)/Ni(II) was irreversible. In vitro antibacterial and antifungal activity against five bacterial strains (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, and Proteus mirabilis) and five fungal strains (Candida albicans, Candida glabrata, Candida tropicalis, Candida krusei, and Candida parapsilosis) showed no antifungal activity but moderate antibacterial activity on E. coli, S. aureus, P. aeruginosa, and P. mirabilis bacterial strains. Antioxidant studies reveal that the ligand and its Cu(II) complex are more potent than Co(II) and Ni(II) complexes to eliminate free radicals.

Novel Nano Copper Complexes of a New Schiff Base: Green Synthesis, a New Series of Solid Cr(II), Co(II), Cu(II), Pd(II) and Cd(II) Chelates, Characterization, DFT, DNA, Antitumor and Molecular Docking Studies

“…X‐ray powder diffractometry (XRD) techniques [ 24 ] were carried out for Cu nano complexes prepared in different media (Figure 6). The diffraction peaks for all Cu nano complexes (except for Cu nano complex prepared in Corchorus olitorius ) are sharp and intense, which confirm the crystalline nature of these nano complexes.…”

Schiff bases as analytical tools: synthesis, chemo-sensor, and computational studies of 2-aminophenol Schiff bases

“…12e revealed two pairs of peaks as two distinct steps of reduction in the forward scan and oxidation in the reverse scan representing Cu 2+ /Cu + and Cu + /Cu redox couples. The steps and potential values determined are as follows: step I corresponds to the Cu 2+ /Cu + redox pair with cathodic and anodic peak potentials of E pc (I) = +200 mV and E pa (I) = +850 mV, respectively; the peak separation DE p (I) = 650 mV indicates a quasi-reversible behaviour; 56,57 step II corresponds to the Cu + /Cu redox couple with cathodic and anodic peak potentials of E pc (II) = -900 mV and E pa (II) = -50 mV, respectively, with DE p (II) = 850 mV. The latter process is metallic copper deposition during a cathodic scan with a characteristic stripping response on the anodic scan for copper dissolution.…”

“…The appearance of a slightly resolved irreversible anodic peak might indicate the slow formation of Zn + during its dissolution after Zn deposition from the forward reduction scan. The steps and potential values displayed were as follows: step I corresponds to the Zn 2+ /Zn redox pair with cathodic and anodic peak potentials of E pc (I) = +100 mV and E pa (I) = +880 mV, respectively, and the peak separation DE p (I) = 780 mV indicates a quasi-reversible behaviour; 56,57 step II corresponds to the Zn/Zn + oxidation with anodic peak potentials of E pa (II) = +325 mV. The shift in oxidation and reduction peaks is also indicative of the complexation of Zn 2+ to MJ 2 .…”

Electrochemical and Biological Studies of Synthesized Schiff base and It's Zinc Complex

“…Electrochemical measurements of GMBPI and its zinc complex have been carried out using 3-electrode cell containing glassy carbon (GCE) as working electrode, Pt as counter electrode and Ag/AgCl as reference electrode. By using alumina suspension, GCE was polished previous to every experiment 12 . The experimental solutions of Schiff base ligand and complex were degassed by passing nitrogen gas for 15 min to remove the dissolved oxygen and were blanketed with the nitrogen gas during the experiments.…”