Synthesis, characterization, biological activities and theoretical studies of schiff bases derived from Isophoronediamine (IPDA) and some aldehyde derivatives

Schiff bases are important compounds in the field of biochemistry due to their antibacterial activity. Schiff bases are formed by the condensation of aldehydes or ketones with a primary amine. In this study, three different L1(4-((((5-amino-1,3,3-trimethylcyclohexyl)methyl)imino)methyl)benzene-1,2,3-triol), L2(2-((((5-amino 1,3,3-trimethylcyclohexyl)methyl)imino)methyl)-4-bromophenol), L3(4-((((5-amino-1,3,3-trimethylcyclohexyl)methyl)imino)methyl)-2-methoxyphenol) Schiff bases were synthesized as a result of the reaction of 3-4 dihydroxysalicylaldehyde, 5-bromosalicylaldehyde and vanillin aldehydes with isophorondiamine (IPDA) in acidic medium. The characterization of the synthesized ligands were carried out experimentally and theoretically using FT-IR, UV-VIS and NMR spectroscopic methods. Theoretical FT-IR, NMR, UV-VIS spectra, HOMO-LUMO, band gap energies, MEP maps and some physicochemical properties of the synthesized ligands were calculated with Gaussian package program using DFT-B3LYP method and 6-311++G(d,p) base set. At the same time, the antibacterial activity of these ligands against S. aureus and E. coli bacteria was investigated using the disk diffusion method. Antibacterial activities were theoretically investigated by molecular docking method using Autodock Vina program. In FT-IR spectroscopy, the v(C=O) stretching vibrations, which show banding in the 1650-1700 cm-1 region in the aldehydes, which are the input materials, are replaced by the v(C=N) stretching vibrations in the Schiff bases, which show a band in the 1600-1650 cm-1 region, the formation of aromatic v(C-H) stretching vibrations above 3000 cm-1 and aliphatic v(C-H) stretching vibrations below 3000 cm-1 are the proofs that the compounds synthesized. The band observed in the 8-9 ppm region in the 1H NMR spectrum represents the C=N group. It was determined that the spectroscopic data obtained experimentally and theoretically were compatible with each other. Antibacterial activities of synthesized ligands against S. aureus and E. coli bacteria were investigated. It was observed that the L3 ligand formed a region on the agar with bacteria and showed antibacterial activity against these bacteria.