Synthesis, infra red characterization and antimicrobial evaluation of Schiff bases derived from 1, 3-diphenylprop-2-en-1-one and 1-phenyl-3-(4-chlorophenyl)-prop-2-en-1-one

Abstract

Chalcones were synthesized via Claisen-Schmidt condensation between various substituted acetophenone and benzaldehyde using 20% cold alcoholic KOH as catalyst. Two Schiff bases were synthesized through the condensation reaction of the synthesized chalcones with 2,4-dinitrophenylhydrazine using concentrated H2SO4 as catalyst. The antimicrobial properties of the Schiff bases were determined using the standard disc diffusion method of anti-microbial sensitivity according to CLSI. The results of anti-microbial analysis were compared to ciprofloxacin and ampicillin as reference standards. The first Schiff base was N-(2,4-Dinitro-phenyl)-N'-(1,3-diphenyl-allylidene)-hydrazine (SB1), a hydrazone of 1,3-diphenylprop-2-en-1-one and the second was N-[3-(4-chloro-phenyl)-1-phenyl-allylidene]-N'-(2,4-dinitro-phenyl)-hydrazine (SB2), a hydrazone of 1-phenyl-3-(4-chlorophenyl)-prop-2-en-1-one. SB1 had a percentage yield of 97.57% and a decomposition temperature of 231-2340C while SB2 gave 98.74% as percentage yield and a melting point of 216-2180C. SB1 showed anti-microbial properties while SB2 showed no anti-microbial properties when both were tested against Staphylococcus aureus and Pseudomonas aeruginosa at a concentration of 10 mg/mL. SB1 had a diameter zone of inhibition of 4-6 mm for P. aeruginosa and 7-9 mm for S. aureus. SB1 was more effective against g positive than g negative bacteria at a concentration of 10 mg/L. The presence of the major absorption band in the range of 350-375 nm, attributable to the n-Ï€* transition of aromatic ketones in the UV spectra of the synthesized chalcones gave credence to their proposed aromatic structure. The presence of strong bands at 1604 cm-1 for SB1 and 1601cm-1 for SB2 and the absence of carbonyl oxygen absorption band in their IR spectra gave credence to the formation of Schiff bases.