Synthesis, spectroscopic characterization, DFT-D2 analysis and BSA binding studies of Co(II), Ni(II) and Cu(II) complexes with a novel Benzothiazole-based ligand

An equimolar mixture of 2-amino-6-methoxybenzothiazole and 2-hydroxy-4-methoxybenzaldehyde was used to produce a Schiff base ligand 5-methoxy-2-(((6-methoxybenzothiazol-2-yl)imino)methyl)phenol, HL, which was then examined by elemental analysis, IR, 1H NMR, 13C NMR and ESI-mass spectrometry. The Co(II), Ni(II) and Cu(II) chlorides, acetates and ligands were combined in ethanol in a molar ratio of 1:1 to create the metal complexes [1-C16H19CoClN2O6S, 2- C18H22CoN2O8S, 3- C16H15NiClN2O4S, 4- C18H18NiN2O6S, 5- C16H15CuClN2O4S and 6- C18H18CuN2O6S]. To identify the structure of all metal complexes 1-6, elemental analysis, molar conductance, electronic spectra and IR spectra were used. The ligand HL functions as an uninegative bidentate via phenolic O- and azomethine N- atoms, according to spectral data. Theoretical studies were performed to investigate the interaction between the metal ions and the ligand HL. This included analysis of the HOMO-LUMO gap to assess electronic properties, Hirshfeld charge distribution to understand electron density changes upon complexation and calculation of the binding energy to evaluate the stability of the metal-ligand complexes. The Co(II) complexes have been given an octahedral geometry, Ni(II) complexes a tetrahedral geometry and Cu(II) complexes a square planar geometry. Studies of the binding of the metal complex to bovine serum albumin (BSA) have been undertaken with the aid of fluorescence and circular dichroism spectrometry.