'On and Off' intercalative binding behaviour of double chain surfactant cobalt(III) complex containing 2, 2-bipyridyl ligand in -Cyclodextrin: A detail approach on Host-guest inclusion of surfactant cobalt(III) complex and CT-DNA binding in micro-heterogeneous medium

The binding interaction of surfactant cobalt(III) complex, cis-[Co(bpy)2(HA)2](ClO4)3, in which bpy is 2,2-bipyr-idine and HA is hexadecylamine or cetylamnine with DNA was through intercalative mode via the long aliphatic chains present in the ligands. The binding was investigated by various techniques, electronic absorption, fluo-rescence spectroscopy, circular dichroism (CD), cyclic voltametry (CV) and viscosimetry measurements. The spectroscopic studies together with cyclic voltammetry and viscosity experiments support that the surfactant cobalt(III) complex binds to calf thymus DNA by intercalation through the aliphatic chain present in the complex into the base pairs of DNA. The presence of bipyridine ligand with larger pi-frame work may also enhance intercalation. UV-vis., spectrum showed 4 nm bathochromic shift of the absorption band at 352 nm along with significant hypochromicity for the absorption band of the complex. The intrinsic binding constants (at below and above CMC are Kb = 2.41 x 105M-1, Kb = 3.12 x 106M-1 respectively) is more in keeping with intercalators and suggests this binding mode. The viscosity measurements showed that the surfactant cobalt(III) complex-DNA