Noncyclic Diaza Ligands and Their Metal Complexes: Synthesis, Characterization, and Biological Studies

Abstract

Condensation reactions involving various ketones and amines formed noncyclic ligands denoted as L^I, L^II, L^III, and L^IV. Ethylenediamine, when reacted with acetophenone, benzoylacetone (in the presence of 70% HClO₄), and benzophenone, resulted in the following noncyclic ligands: (E,E)-N,N-bis(1-phenylethylidene)ethylenediamine (L^I), bis(1-3-hydroxy-3-phenylbut-2-ene-ylidene) (L^II) and (E,E)-N,N-bis(1,1-diphenylmethylidene)ethylenediamine (L^III), respectively. The reaction of benzophenone with 1,3-diaminopropane in a 1:1 ratio in a methanolic solution also led to the synthesis of a noncyclic ligand, (E,E)-N,N-bis(1,1-diphenylmethylidene)propylenediamine (L^IV). All the synthesized noncyclic ligands, except L^II, undergo decomposition during complexation, reverting to the initial ketones and amines. In contrast, L^II exhibits remarkable stability and can form square planar complexes with Ni(II), Cu(II), and Co(II) salts. Additionally, the Co(II) complex can convert into a six-coordinated Co(III) complex, [CoL^II(H₂O)₂](NCS), when it reacts with KNCS. All these ligands and derived metal complexes were characterized, and their antimicrobial properties were evaluated against the selected fungi and bacteria.