Comprehensive Exploration of Water-Soluble Schiff Base Complexes of Ni (II), Cu (II), Mn (II), and Ce (III): Electrochemical, Computational, and Biological Studies

Abstract

Novel water-soluble Ni(II), Cu(II), Mn(II), and Ce(III) complexes of sodium 4-hydroxy-3-((2-picolinoylhydrazineylidene)methyl)benzenesulfonate ligand (NaH₂PH) were synthesized and characterized by the different analytical methods and spectroscopic techniques as well as magnetic measurements. The chemical structures of the studied chelates were supported by computational studies using DFT calculation. The ligand acts as a mono-negative tridentate (ONN) ligand in the copper (II) complex by (C=N)_py, (C=N)_az, and the deprotonated enolic oxygen atom (C-O). In [Mn₂(NaPH)Cl₂(H₂O)₂] complex, NaH₂PH ligand acts as a bi-negative tetradentate (ONNO) ligand via deprotonated (OH)_phenolic and (C=N*) groups around the first Mn (II), the (HO)_enolic, and (C=N)_az groups coordinated to another Mn(II). As a mono-negative bidentate (ON) ligand, the NaH₂PH ligand functions in the [Ni(NaHPH)Cl(H₂O)]·3H₂O complex. The ligand functions as a bi-negative tetradentate (ONNO) ligand in the [Ce(NaPH)Cl(H₂O)]·3H₂O complex. The isotropic shape of the ESR spectrum of [Cu(NaHPH)(H₂O)₂Cl].H₂O complex confirmed the octahedral geometry around the copper(II) ion. The voltammogram of the Cu(II) and Mn(II) ions exhibited two oxidation and two reduction waves. The antiradical potencies discovered have good radical scavenging activities against ABTS and DPPH radicals. Antimicrobial activities of the isolated complexes have been assessed against selected microorganism. According to the molecular docking studies, the Mn(II) complex shows higher interaction against MCF-7 (PDB ID: 3W2S), which has a good agreement with experimental data.