title: Synthesis, structure, magnetism and nuclease activity of tetranuclear copper(II) phosphonates containing ancillary 2,2'-bipyridine or 1,10-phenanthroline ligands.
abstract: The reaction of cyclohexylphosphonic acid (C(6)H(11)PO(3)H(2)), anhydrous CuCl(2) and 2,2'-bipyridine (bpy) in the presence of triethylamine followed by a metathesis reaction with KNO(3) afforded [Cu(4)(mu-Cl)(2)(mu(3)-C(6)H(11)PO(3))(2)(bpy)(4)](NO(3))(2) (1). In an analogous reaction involving Cu(OAc)(2).H(2)O, the complex [Cu(4)(mu-CH(3)COO)(2)(mu(3)-C(6)H(11)PO(3))(2)(2,2'-bpy)(4)](CH(3)COO)(2) (2) has been isolated. The three-component reaction involving Cu(NO(3))(2).3H(2)O, cyclohexylphosphonic acid and 2,2'-bipyridine in the presence of triethylamine afforded the tetranuclear assembly [Cu(4)(mu-OH)(mu(3)-C(6)H(11)PO(3))(2)(2,2'-bpy)(4) (H(2)O)(2)](NO(3))(3) (3). Replacing 2,2'-bipyridine with 1,10-phenanthroline (phen) in the above reaction resulted in [Cu(4)(mu-OH)(mu(3)-C(6)H(11)PO(3))(2)(phen)(4)(H(2)O)(2)](NO(3))(3) (4). In all the copper(II) phosphonates (1-4) the two phosphonate ions bridge the four copper(II) ions in a capping coordination action. Each phosphonate ion bridges four copper(II) ions in a mu(4), eta(3) coordination mode or 4.211 of the Harris notation. Variable-temperature magnetic studies on reveal that all four complexes exhibit moderately strong intramolecular antiferromagnetic coupling. The DNA cleavage activity of complexes 1-4 is also described. Compounds 1 and 3 were able to completely convert the supercoiled pBR322 DNA form I to nick form II without any co-oxidant. In contrast, 50% conversion occurred with and 40% with 4. In the presence of magnesium monoperoxyphthalate all four compounds achieved rapid conversion of form I to form II.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, UP 208016, India. vc@iitk.ac.in
authors.forename: Vadapalli
authors.initials: V
authors.lastname: Chandrasekhar
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Azhakar
authors.forename: Tapas
authors.initials: T
authors.lastname: Senapati
authors.forename: Pakkirisamy
authors.initials: P
authors.lastname: Thilagar
authors.forename: Surajit
authors.initials: S
authors.lastname: Ghosh
authors.forename: Sandeep
authors.initials: S
authors.lastname: Verma
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Boomishankar
authors.forename: Alexander
authors.initials: A
authors.lastname: Steiner
authors.forename: Paul
authors.initials: P
authors.lastname: Kögerler
mesh_terms: D002412:Cations; D018360:Crystallography, X-Ray; D008024:Ligands; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D002412:Cations; D008024:Ligands; D009942:Organometallic Compounds