Liquid-assisted Mechanochemical Conversion of 2-hydroxy-3- methoxybenzaldehyde and Some Primary Aromatic Amines to Corresponding Schiff bases

Abstract

In this paper, two Schiff bases of different solid primary aromatic amines were successfully synthesized using 1:1 and 2:1 molar ratio of 2-hydroxy-3-methoxybenzaldehyde to solid amine, by Liquid-assistant grinding. The
Schiff-bases were investigated by analytical and spectroscopic techniques using FT-IR, Powder X-ray Diffraction Energy Dispersive X-ray (EDX) Melting point and CHN microanalysis. The Schiff bases were found to be soluble in polar solvent such as methanol and ethanol but insoluble in non-polar solvent such as hexane. Evidence from Infrared spectral study indicated that, the characteristics band attributed to aldehyde stretching disappeared on the final Schiff bases and the new absorption band at 1624 - 1644 cm^-1 was due to the ν(C=N) stretching vibration, which is the characteristic band of Schiff base. The Powder-XRD analysis reveals that, the PXRD patterns of the Schiff bases were different from their respective starting materials which indicate the formation of new phase of the product. The elemental  microanalysis of the Schiff base ligand is consistent with the calculated results from the empirical formula of the proposed structure of each  compound. The antimicrobial activities of the synthesized Schiff base were tested using agar well diffusion method, against different strains of bacterial and fungal isolates. The antimicrobial results indicated that, the antibacterial activity of the (H2L¹) Schiff base ligand was found to be more effective against Escherichia coli.

Keywords: Azomethine, Liquid-assistant grinding, Mechanochemistry, Powder x-ray, Schiff base