Kalligundi R. Sangeetha Gowda1 and M. Giridhar

Fe(II) complexes [Fe(mqs)(B)2](PF6)(1)-(3) of  2-thiol 4-methylquinoline and phenanthroline bases (B), viz 1,10-Phenanthroline (phen in 1), Dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2) and Dipyrido[3,2-a:2′,3′-c]phenazine (dppz in 3) have been prepared and characterized. The DNA-binding behaviors of these three complexes were investigated by absorption spectra, viscosity measurements and thermal denaturation studies. The DNA-binding constants for complexes 1, 2 and 3 were determined to 2.4 x104, 1.3 x 105 and 4.2 x105 M-1, respectively. The experimental results suggest that these complexes interact with DNA through groove binding mode. The photo induced cleavage studies shows that the complexes possess photonuclease property against pUC19 DNA under UV–Visible irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. Antibacterial PDT for E. coli strain, the control group showed a significantly higher (p0.05) in the CFU counts. The complex (3)/Light group presented a significant decrease in the CFU counts (p