Synthesis, Spectroscopic Characterization and DNA Binding Interactions of Co(II) Complexes with Two Twelve-Membered Tetraaza Macrocyclic Ligands

This study reports the synthesis and characterization of Co(II) complexes with two twelve-membered tetraaza macrocyclic ligands:(1) 2,3,8,9-tetraphenyl-5,11-diethyl-1,4,7,10-tetraaza- cyclododeca-1,3,7,9-tetraene (TPDET) and (2) 6,7,14,15- tetraphenyldibenzo[b,h]-1,4,7,10-tetraazacyclododeca-1,3,5,7,9,11-hexaene (TPDBT). The ligands were synthesized via condensation reactions, and chloro, nitrato and thiocyanato Co(II) complexes were prepared separately. Characterization was performed using elemental analysis, FT-IR, UV-Vis, 1H NMR, EPR, and magnetic susceptibility measurements, Spectral studies and various other physico-chemical techniques suggested octahedral geometry for all the complexes. DNA interactions were investigated using UV-Vis absorption spectroscopy and viscosity measurements, revealing intercalative binding modes with calf thymus DNA (CT-DNA). The binding constants (Kb) for the reported complexes were found in the range 1.2 × 10⁵ to 2.3 × 10⁵ M⁻¹. These findings suggested potential applications in bioinorganic chemistry and drug design.