Electrochemical studies of DNA interaction and antimicrobial activities of MnII, FeIII, CoII and NiII Schiff base tetraazamacrocyclic complexes

Tetraazamacrocyclic complexes of Mn^II, Fe^III, Co^II and Ni^II have been synthesized by template method. These tetraazamacrocycles have been analyzed with various techniques like molar conductance, IR, UV-vis, mass spectral and cyclic voltammetric studies. On the basis of all these studies, octahedral geometry has been assigned to these tetraazamacrocyclic complexes. The DNA binding properties of these macrocyclic complexes have been investigated by electronic absorption spectra, fluorescence spectra, cyclic voltammetric and differential pulse voltammetric studies. The cyclic voltammetric data showed that i_pc and i_pa were effectively decreased in the presence of calf thymus DNA, which is a strong evidence for the interaction of these macrocyclic complexes with the calf thymus DNA (ct-DNA). The heterogeneous electron transfer rate constant found in the order: K_Co^II>K_Ni^II>K_Mn^II which indicates that Co^II macrocyclic complex has formed a strong intercalated intermediate. The Stern-Volmer quenching constant (K_SV) and voltammetric binding constant were found in the order K_SV(Co^II)>K_SV(Ni^II)>K_SV(Mn^II) and K⁺(Co^II)>K⁺(Ni^II)>K⁺(Mn^II) which shows that Co^II macrocyclic complex exhibits the high interaction affinity towards ct-DNA by the intercalation binding. Biological studies of the macrocyclic complexes compared with the standard drug like Gentamycin, have shown antibacterial activities against E. coli, P. aeruginosa, B. cereus, S. aureus and antifungal activity against C. albicans.