Synthesis and characterization of new unsymmetrical bis-Schiff bases

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Faculty of Science, University of Ilorin


The literature is replete with symmetrical tetradentate bis-Schiff bases of 1,2-diamines with o-hydroxyaldehyde or ketones, but less attention has been focused on the analogous unsymmetrical tetradentate ones. Unsymmetrical Schiff bases of aromatic diamines are very difficult to obtain and are not easily isolated. This class of Schiff bases have very simple synthetic procedure and versatile coordination behavior. Metal complexes containing these Schiff bases in their structure usually possess exceptional antibacterial, antifungal and antitumor activities including anti-HIV activity. In this regard, two new unsymmetrical bis-Schiff bases, (Z)-N-(2-nitrophenyl)-N'-(2-((Z)-(2-oxoindolin-3-ylidene)amino)phenyl)acetimidamide (1) and (Z)-N-(2-nitrophenyl)-N'-((Z)-N-(2-oxoindolin-3-ylidene)carbamimidoyl)acetimidamide (2), were prepared from the condensation reactions of 2’-nitroacetanilide and 1H-indole-2,3-dione with o-phenylenediamine and guanidinium ions in ethanol. The corresponding symmetrical bis-Schiff bases (Z,Z)-1,3-bis(2-oxoindolin-3-ylidene)guanidine (3) and N-((2-(1-iminoethyl)-2-(2-nitrophenyl)hydrazinyl)methyl)-N-(2-nitrophenyl)acetimidamide (4) were also prepared. The data obtained from the elemental, IR and NMR spectroscopic analyses were used to propose structures for the four compounds.



Bis-Schiff bases, guanidinium ions, 2’-nitroacetanilide, 1H-indole-2,3-dione, o-phenylenediamine