Synthesis, characterization, biological activities and theoretical studies of schiff bases of 4-Hydroxysalicylaldehyde and Isophorondiamine

Nowadays, Schiff bases have an important place due to their easy synthesis and their use in many fields such as chemistry, biology, pharmaceutical chemistry. Schiff bases are formed when any primary amine reacts with an aldehyde or a ketone under certain conditions. It is known that Schiff bases are effective in application areas such as antibacterial, antifungal, anticancer, antioxidant, anti-inflammatory, antimalarial, antiviral activity. Considering this situation, synthesizing new schiff bases, performing their experimental and theoretical characterization, and examining their experimental and theoretical antibacterial activities were considered. In this study, 4 hydroxy salicylaldehyde and isophorondiamine (IPDA) were used in 1:1, 2:1 ratios to synthesize (((((5-amino1,3,3trimethylcyclohexyl)methyl)imino)methyl) benzene-1,3diol (L1) and ((((2, 4-dihydroxybenzylidene)amino)1,3,3trimethylcyclohexyl)methylimino)methyl)benzene-1,3-diol (L2) ligands. The synthesized ligands were characterized using FT-IR, Uv-Vis., NMR spectroscopic methods and elemental analysis. Optimization of synthesized ligands, bond angles, bond lengths, HOMO-LUMO, band gap energies, MEP maps, some physicochemical properties and spectroscopic data such as NMR, elemental analysis FT-IR and Uv-Vis. were calculated using the DFT/B3LYP method 6-311++G(d,p) base set with the help of the gaussian package program. To support the characterization of the L2 ligand, its structure was elucidated by elemental analysis. Antibacterial properties of the synthesized ligands against E.coli and S.aureus bacteria were investigated using disk diffusion method. The antibacterial properties of the synthesized ligands against E.coli and S.aureus bacteria were calculated with the autodock vina program using the molecular docking method. When the FT-IR spectroscopy of the synthesized ligands was examined, it was observed that the carbonyl (C=O) band in 4 hydroxy salicylaldehyde disappeared and replaced by the imine (C=N) band on the Schiff basis. The band in the region above 3000 cm-1 wavelength indicates the aromatic ring and the band in the region below 3000 cm-1 wavelength indicates aliphatic groups. The peaks of the synthesized ligands in the range of 8-8.50 ppm in 1H-NMR spectroscopy and in the range of 160-170 ppm in 13C-NMR spectroscopy are indicative of the imine (-CH=N-) group. The fact that the synthesized ligands did not form any area on the agar with bacteria indicates that these ligands do not have antibacterial activity