title: Tri-, tetra-, and hexanuclear copper(II) phosphonates containing N-donor chelating ligands: synthesis, structure, magnetic properties, and nuclease activity.
abstract: Reaction of Cu(ClO(4))(2).6H(2)O with cyclopentyl phosphonic acid and 2,2'-bipyridine (bpy) in presence of triethylamine afforded a trinuclear compound [Cu(3)(C(5)H(9)PO(3))(2)(bpy)(3)(MeOH)(H(2)O)](ClO(4))(2) (2). The latter dimerizes to a hexanuclear derivative [Cu(6)(C(5)H(9)PO(3))(4)(bpy)(6)(MeOH)(4)](ClO(4))(4) (1) under prolonged reaction conditions. Reaction of CuCl(2) with cyclopentyl phosphonic acid and 2,2'-bipyridylamine (bpya) affords a tetranuclear derivative [Cu(4)(C(5)H(9)PO(3))(2)(mu-Cl)(2)(bpya)(4)](Cl)(2), (MeOH)(2) (3). Reaction of the latter with NaClO(4) also affords a trinuclear compound [Cu(3)(C(5)H(9)PO(3))(2)(mu-Cl)(bpya)(3)(H(2)O)](ClO(4)) (4). Double and single-bridged hexanuclear species, [{Cu(3)(C(5)H(9)PO(3))(2)(bpy)(3)(bpp)}(MeOH)(2)(H(2)O)(CH(2)Cl(2))(ClO(4))(2)](2) (5), [{Cu(3)(i-PrPO(3))(2)(bpy)(3)(4.4'-bpy)(H(2)O)}(H(2)O)(2)(ClO(4))(2)](2) (6), [{Cu(3)(C(5)H(9)PO(3))(2)(bpya)(3)(4.4'-bpy)(H(2)O)}(MeOH)(H(2)O)(ClO(4))(2)](2) (7), and [Cu(6)(t-BuPO(3))(4)(phen)(6)(4,4'-bpy)(MeOH)(4)](CH(2)Cl(2))(H(2)O)(ClO(4))(4) (8) (phen = 1,10-phenanthroline) were obtained by the reaction of an in situ generated trinuclear complex with appropriate bridging ligands 4,4'-bipyridine (4,4'-bpy) or 1,3-bis(4-pyridyl)propane (bpp). ESI-MS studies of these complexes reveal that 2-4 retain their structures in solution. Molecular structures of 2-8 were determined by X-ray crystallography. All the compounds reveal a capping coordination mode by tridentate phosphonate [RPO(3)](2-) ligands. Detailed magnetic studies on 2 and 4-8 reveal intramolecular antiferromagnetic interactions between Cu(II) S = 1/2 spins. 2 and 4 are excellent artificial nucleases and can convert supercoiled plasmid DNA (pBR322) into its nicked form without the aid of an external oxidant.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India. vc@iitk.ac.in
authors.forename: Vadapalli
authors.initials: V
authors.lastname: Chandrasekhar
authors.forename: Tapas
authors.initials: T
authors.lastname: Senapati
authors.forename: E Carolina
authors.initials: EC
authors.lastname: Sañudo
authors.forename: R
authors.initials: R
authors.lastname: Clérac
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008024:Ligands; D008280:Magnetics; D015394:Molecular Structure; D063065:Organophosphonates / Q000138:chemical synthesis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002614:Chelating Agents; D008024:Ligands; D063065:Organophosphonates; D003300:Copper