title: Synthesis, characterization, X-ray structure and DNA photocleavage by cis-dichloro bis(diimine) Co(III) complexes.
abstract: Complexes of the type [Co(LL)2Cl2]Cl, where LL = N,N'-ethylenediamine (en), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (phendione) and dipyrido[3,2-a:2',3'-c]phenazine (dppz) have been synthesized and characterized by elemental analyses, IR, UV-visible and NMR spectroscopy. Crystal structure of [Co(phendione)2Cl2]Cl x 0.5 HCl x 3.5 H2O has been solved and refined to R = 0.0552. The crystal is monoclinic with space group C2/c; a = 25.730(2) A, b = 12.375(1) A, c = 18.979(2) A, beta = 119.925(1) degrees and Z = 8. The DNA binding characteristics of the complexes, investigated by covalent binding assay, viscosity measurements and competitive binding fluorescence measurements show that the complexes interact with DNA covalently except the complex containing the planar dppz ligand which intercalates within the base pairs of DNA. The complexes containing en, phen and phendione cleave plasmid pBR 322 DNA upon irradiation under aerobic conditions while the complex containing the dppz ligand cleaves DNA upon irradiation under inert atmosphere. Molecular modeling studies show that the minimized structure of [Co(phendione)2Cl2]+, maintained the octahedral structure while binding to the N7 of guanines and the ligand fits into the major groove without disrupting the helical structure of the B-DNA.
authors.affiliation: Department of Chemistry, University of Pune, Ganeshkhind Road, Pune 411007, India.
authors.forename: Smita
authors.initials: S
authors.lastname: Ghosh
authors.forename: Archika C
authors.initials: AC
authors.lastname: Barve
authors.forename: Anupa A
authors.initials: AA
authors.lastname: Kumbhar
authors.forename: Avinash S
authors.initials: AS
authors.lastname: Kumbhar
authors.forename: Vedavati G
authors.initials: VG
authors.lastname: Puranik
authors.forename: Prasanna A
authors.initials: PA
authors.lastname: Datar
authors.forename: Uddhavesh B
authors.initials: UB
authors.lastname: Sonawane
authors.forename: Rajendra R
authors.initials: RR
authors.lastname: Joshi
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry; D001667:Binding, Competitive; D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D002713:Chlorine / Q000737:chemistry*; D002850:Chromatography, Gel; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004249:DNA Damage; D005029:Ethylenediamines / Q000737:chemistry; D007097:Imines / Q000737:chemistry*; D008027:Light; D008958:Models, Molecular; D008968:Molecular Conformation; D010618:Phenanthrolines / Q000737:chemistry; D010619:Phenazines / Q000737:chemistry; D010777:Photochemistry; D010782:Photolysis; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014783:Viscosity
chemical_list: D002614:Chelating Agents; D005029:Ethylenediamines; D007097:Imines; D010618:Phenanthrolines; D010619:Phenazines; C443808:dipyrido(3,2-a-2',3'-c)phenazine; C037153:1,10-phenanthroline-5,6-dione; D003035:Cobalt; D002713:Chlorine; D015082:2,2'-Dipyridyl; C031234:ethylenediamine; D004247:DNA; C025205:1,10-phenanthroline