A new complex [Co(phen) 2 tpphz] 3+ (where tpphz is the planar ligand tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine) has been synthesized and characterized by elemental analysis, IR spectra, molar conductivity, 1 H NMR spectra, AgNO 3 titrations, UV and fluorescence spectra. The interaction of the complex with calf thymus DNA has been investigated using absorption and emission spectroscopy, viscosity, cyclic voltammetry and photochemistry. The complex shows absorption hypochromicity, fluorescence enhancement, and the specific viscosity increases when binding with calf thymus DNA. The binding constant is 3.75×10 4 M −1 . CV measurements show a change in peak current with addition of DNA. When irradiated at 254.7 nm, [Co(phen) 2 tpphz] 3+ induces strand scissions in plasmid DNA.