Multistep synthesis of novel tris-Schiff bases – azobenzene hybrids as antimicrobial agents

The target compounds 4-(((1H-heteraryl)imino)methyl)-N,N-bis(4-(((4-((4-nitrophenyl) diazenyl)phenyl)imino)methyl)phenyl)aniline (7a-q) were prepared starting with 4,4′-diformyltriphenyl amine (2) which subjected to react with N-bromosuccinimide to give bromodiformyltriphenyl amine (4). Compound 4 reacted with two moles of 4-nitro-4′-aminoazobenzene to give the di-Schiff base 5. Compound 5 converted to its corresponding formyl derivative 6 by reaction with n-BuLi. The reaction of the formyl derivative 6 with seventeen amino heteraryl compounds afforded the target compounds 7a-q. All the newly prepared compounds were characterized by different spectroscopic and elemental analyses. Compounds 7a-q were screened for their antimicrobial activities against yeast-like fungi (C. albicans), Gram-negative (GN) bacteria (P. aeruginosa and E. coli), and Gram-positive (GP) bacteria (S. thuringiensis and B. subtilis). Compounds 7d, 7k, 7l, and 7q showed the highest activity against Gram-positive bacteria. The results of antimicrobial activity showed that it is highly affected by the used amine basicity.