In vitro antibacterial, radical scavenging and solvato-chromism properties of some 4-((4-R-phenyldiazenyl-2-(pyridin-2-ylimino)methyl) phenols

The 4-((4-R-phenyldiazenyl-2-(pyridin-2-ylimino) methyl) phenols were synthesized from the reaction of 5-((4-R-phenyl)diazenyl)-2-hydroxybenzaldehyde with aminopyridines in absolute ethanol and characterized by elemental analysis, mass, FT-IR, UV and NMR spectroscopy. The absorption maxima of synthesized compounds show bathochromic shift in various solvents. The nature of substitutions, solvent environment, hydrogen bonds, temperature, pH and dipole moment of the molecules are the key factors in deciding the solvato-chromism of azo–azomethine dyes. Antibacterial activity was studied by disk diffusion and broth microdilution methods. Diphenylpicrylhydrazyl assay was used to determine the radical scavenging properties. Compounds having electron donating groups in the aryl azo component showed significant antibacterial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Klebsiella pneumonia. Derivative 2-((E)-(pyridin-4-ylimino) methyl)-4-((E)-p-tolyldiazenyl) phenol (2h) with excellent antibacterial activity showed the highest scavenging effect, while the minimum antibacterial and scavenging activity was observed by 4-((E)-(4-chlorophenyl)diazenyl)-2-((E)-(pyridin-2-ylimino)methyl) phenol (2f) having electron withdrawing Cl substituent in the aryl azo component. The antibacterial and scavenging activity of synthesized derivatives are affected by the nature and position of the substituent groups and position of the nitrogen atoms in the pyridine ring.