Syntheses, Characterization, and Antimicrobial Studies of Ni(II), Cu(II), and Co(III) Complexes with an N-Pendant Azamacrocyclic Chelator

Abstract Condensation of 1,2-diamino propane with acetone in the presence of perchloric acid furnished a 14-membered octamethyl tetraazamacrocycle, Me8[14]diene•2HClO4, which further produced a mixture of isomeric ligands, Me8[14]anes (LA, LB, and LC), on reduction with NaBH4 and subsequent extraction with CHCl3 (pH > 12). The isomers were separated by fractional crystallization from xylene. Interaction of LC with excess acrylonitrile afforded an N-pendant derivative, LCX, in which two cyanoethyl groups were attached to less crowded nitrogen atoms (N4 and N11). Upon the interaction of LCX with Ni(CH3COO)2•4H2O, Cu(ClO4)₂•6H2O, and Co(CH3COO)₂•4H₂O, square planar [Ni(LCX)](ClO4)2 and [Cu(LCX)](ClO4)2 and octahedral trans-[Co(LCX)Cl2](ClO4), respectively, were produced. Axial substitution reactions of trans-[Co(LCX)Cl2](ClO4) with KCNS, KM (M = NO3, Br, or I), and NaNO2 afforded substituted trans-[Co(LCX)(NCS)2](SCN), trans-[CoLCX(X)2](ClO4), and trans-[Co(LCX)(NO2)2](ClO4), respectively. The ligand and corresponding metal complexes were characterized based on the analytical, spectroscopic, magnetic moment, and molar conductivity data. Gram-positive and gram-negative bacteria and different fungi were used to evaluate the antibacterial and antifungal activities of the ligand and its metal complexes.