Synthesis, characterization and dna interaction studies of (N,N'-Bis(5-phenylazosalicylaldehyde)-ethylenediamine) cobalt(II) complex

Abstract

In the present study, at first, azo Schiff base ligand of (N,N'-bis(5-phenylazosalicylaldehyde)-ethylenediamine) (H2L) has been synthesized by condensation reaction of 5-phenylazosalicylaldehyde and ethylenediamine in 2:1 molar ratio, respectively. Then, its cobalt complex (CoL) was synthesized by reaction of Co(OAc)2·4H2O with ligand (H2L) in 1:1 molar ratio in ethanol solvent. This ligand and its cobalt complex containing azo functional groups were characterized using elemental analysis, 1H-NMR, UV-vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and CoL complex was investigated in 10 mM Tris/HCl buffer solution, pH = 7 using UV-vis absorption, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of CoL complex with ct-DNA was found to be (2.4 ± 0.2) × 104M -1. The thermodynamic parameters were calculated by van't Hoff equation.The enthalpy and entropy changes were 5753.94 ± 172.66 kcal/mol and 43.93 ± 1.18 cal/mol·K at 25°C, respectively. Thermal denaturation experiments represent the increasing of melting temperature of ct-DNA (about 0.93°C) due to binding of CoL complex. The results indicate that the process is entropy- driven and suggest that hydrophobic interactions are the main driving force for the complex formation.