title: Cobalt complexes of terpyridine ligand: crystal structure and photocleavage of DNA.
abstract: Two new cobalt complexes, [Co(pytpy)(2)](ClO(4))(2), 1, and [Co(pytpy)(2)](ClO(4))(3), 2 where pytpy=pyridine terpyridine, have been synthesized and characterized. Single-crystal X-ray structure of both the complexes has been resolved. The structure shows the complexes to be a monomeric cobalt(II) and cobalt(III) species with two pytpy ligands coordinated to the metal ion to give a six coordinate complex. Both cobalt(II) and cobalt(III) complexes crystallize in meridional configuration. The interaction of these complexes with calf thymus DNA has been explored by using absorption, emission spectral, electrochemical studies and viscosity measurements. From the experimental results the DNA binding constants of 1 and 2 are found to be (1.97+/-0.15)x10(4)M(-1) and (2.7+/-0.20)x10(4)M(-1) respectively. The ratio of DNA binding constants of 1 and 2 have been estimated to be 0.82 from electrochemical studies, which is in close agreement with the value of 0.73 obtained from spectral studies. The observed changes in viscosity of DNA in the presence of increasing amount of complexes 1 and 2 suggest intercalating binding of these complexes to DNA. Results of DNA cleaving experiments reveal that complex 2 efficiently cleaves DNA under photolytic conditions while complex 1 does not cleave DNA under similar conditions.
authors.affiliation: Chemical Laboratory, Central Leather Research Institute, Adyar, Chennai 600020, India.
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Indumathy
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Radhika
authors.forename: Mookandi
authors.initials: M
authors.lastname: Kanthimathi
authors.forename: T
authors.initials: T
authors.lastname: Weyhermuller
authors.forename: Balachandran
authors.initials: B
authors.lastname: Unni Nair
mesh_terms: D000818:Animals; D002417:Cattle; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010782:Photolysis; D011725:Pyridines / Q000737:chemistry; D013057:Spectrum Analysis; D014783:Viscosity
chemical_list: D007364:Intercalating Agents; D009942:Organometallic Compounds; D011725:Pyridines; D003035:Cobalt; D004247:DNA; C427203:calf thymus DNA