Antibacterial and antifungal studies of macrocyclic complexes of trivalent transition metal ions with their spectroscopic approach.

A new series of complexes of the type [M(C24H16N4)X]X2, where M = Cr(III), Fe(III), and Mn(III), X = Cl-, NO3-, and CH3COO-, has been synthesized by template condensation of 1,8-diaminonaphthalene and glyoxal in the presence of trivalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analysis, conductance measurements, magnetic measurements, and electronic, NMR, IR, and mass spectral studies. On the basis of these studies, a five-coordinate square pyramidal geometry for all of these complexes has been proposed. All the synthesized metal complexes were also tested for their in vitro antimicrobial activities against some bacterial strains, viz. Bacillus subtilis, Bacillus stearothermophilus (gram-positive bacteria), Escherichia coli, and Pseudomonas putida (gram-negative bacteria), and some fungal strains, viz. Aspergillus flavus and Aspergillus niger. The results obtained were compared with standard antibiotics: chloramphenicol, streptomycin, and the antifungal drug cyclohexamide. Some of the tested complexes showed remarkable antimicrobial activities.