title: Metamorphosis of a butterfly: synthesis, structural, thermal, magnetic and DFT characterisation of a ferromagnetically coupled tetranuclear copper(II) complex.
abstract: The reaction in water of Cu(OH)(2) with 2,2'-bipyridine (bipy) and (NH(4))(2)HPO(4) in a 4 : 4 : 2 molar ratio under an inert atmosphere leads to the formation of a tetranuclear copper(II) complex of formula {[(H(2)O)(2)Cu(4)(bipy)(4)(mu(4)-PO(4))(2)(mu(2)-OH)] x 0.5 HPO(4) x 15.5 H(2)O}, 1, with butterfly topology. The structure of the tetranuclear core in 1 consists of four crystallographically unique copper(II) ions in approximate square-pyramidal geometry with each coordinated to a bipy ligand and interacting through two mu(4)-O,O',O''-phosphate bridges. Additional bridging between Cu(3) and Cu(4) is provided by a hydroxide ligand, whereas two water molecules cap the Cu(1) and Cu(2) square pyramids to yield a N(2)O(3) chromophore at each copper atom. Adjacent tetranuclear units align in anti-parallel fashion where proximate metal-bound water molecules interact with each other through both intra- and inter-molecular H-bonding to link two such clusters. These pairs then further associate through pi[...]pi interactions between bipy ligands to form a 2D sheet with neighbouring sheets separated by H-bonded lattice water molecules, which form a 2D H-bonded network. Variable-temperature magnetic susceptibility measurements performed upon 1 reveal net intramolecular ferromagnetic coupling between the copper(II) ions and this is supported and rationalized by a DFT study.
authors.affiliation: Department of Chemistry, Syracuse University, Syracuse, New York, 13244-4100, USA. rpdoyle@syr.edu
authors.forename: Robert P
authors.initials: RP
authors.lastname: Doyle
authors.forename: Thomas
authors.initials: T
authors.lastname: Bauer
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.forename: Joan
authors.initials: J
authors.lastname: Cano
authors.forename: Mark
authors.initials: M
authors.lastname: Nieuwenhuyzen
authors.forename: Paul E
authors.initials: PE
authors.lastname: Kruger
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008280:Magnetics; D008956:Models, Chemical; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D013696:Temperature
chemical_list: D009942:Organometallic Compounds; D003300:Copper