Synthesis, Spectral Characterization, Antitumor, Antioxidant, and Antimicrobial Studies of New Potential ONS Schiff Base Complexes

Novel Co(II), Ni(II), Cu(II), and Zn(II) complexes derived from 2-aminopyridine-3-thiol and 4-oxo-4H-chromene-3-carbaldehyde were synthesized and characterized by spectroscopic (IR, H-1 NMR, UV-vis, ESR, and MS) and other analytical methods. Molar conductance data and magnetic susceptibility measurements provide evidence for the monomeric and monobasic nature of the complexes. The molar conductance measurement of the complexes in DMSO corresponds to their non-electrolytic nature. All the complexes are of high-spin type. On the basis of the different spectral studies, the six-coordinated geometry may be assigned for all the complexes. IR spectral studies indicate the binding sites of the ligand with the metal ion. The Schiff base acts as tridentate ligand coordinated through deprotonated thiolic (SH) sulfur, azomethine (-CH=N-) nitrogen, and carbonyl (-C=O) oxygen atoms. The ligand field parameters were calculated for Co(II) and Ni(II) complexes and their values were found to be in the range reported for an octahedral structure. The data show that the complexes have an ML2-type composition. The activation thermodynamic parameters are calculated using the Coast-Redfern, Horowitz-Metzger (HM), Piloyan-Novikova (PN), and Broido equations. The X-ray diffraction data suggest a triclinic system for all compounds. Different surface morphologies were identified from SEM micrographs. Human tumor cell lines A427 (lung cancer cell line), LCLC-103H (large cell lung cancer), SISO (uterine adenocarcinoma), and 5637(human bladder carcinoma) grown in RPMI-1640 medium were elevated. The biological screening data show that the complexes show growth inhibitory activity against various microorganisms. The octahedral geometry of the complexes is confirmed using density functional theory (DFT) from DMOL3 calculations, electronic and magnetic moment measurements, ESR, and ligand field parameters.