title: Synthesis and structural and magnetic characterization of {[(phen)(2)Ni](2)(micro-P(2)O(7))} . 27H(2)O and {[(phen)(2)Mn](2)(micro-P(2)O(7))} . 13H(2)O: rare examples of coordination complexes with the pyrophosphate ligand.
abstract: The reaction in water of M(II) [M = Ni or Mn] with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometry resulted in the crystallization of dinuclear complexes featuring the heretofore rare bridging pyrophosphate. Single-crystal X-ray diffraction studies revealed the complexes to be {[(phen)2Ni]2(micro-P2O7)} . 27H2O (1) and {[(phen)2Mn]2(micro-P2O7)} . 13H2O (2) where the asymmetric M(phen)2 units are bridged by bis-bidentate pyrophosphate, each metal ion exhibiting a distorted octahedral geometry. The bridging pyrophosphate places adjacent metal centers at 5.031 A in 1 and 4.700 A in 2, and its conformation also gives rise to an intramolecular pi-pi interaction between two adjacent phen ligands. Intermolecular pi-pi interactions between phen ligands from adjacent dinuclear complexes create an ornate 3D network in 1, whereas a 2D sheet results in 2. The hydrophilic nature of the pyrophosphate ligand leads to heavy hydration with the potential solvent-accessible area for 1 and 2 accounting for 45.7% and 26.4% of their unit cell volumes, respectively. Variable-temperature magnetic susceptibility measurements on polycrystalline samples of 1 and 2 revealed net weak intramolecular antiferromagnetic coupling between metal centers in both compounds with J = -3.77 cm(-1) in 1 and J = -0.88 cm(-1) in 2, the Hamiltonian being defined as H = -JSA.SB. The ability of the bis-bidentate pyrophosphate to mediate magnetic interactions between divalent first row transition metal ions is discussed bearing in mind the number and nature of the interacting magnetic orbitals.
authors.affiliation: Department of Chemistry, Syracuse University, Syracuse, NY 13244-4100, USA.
authors.forename: Oluwatayo F
authors.initials: OF
authors.lastname: Ikotun
authors.forename: N Gabriel
authors.initials: NG
authors.lastname: Armatus
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.forename: Paul E
authors.initials: PE
authors.lastname: Kruger
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.forename: Mark
authors.initials: M
authors.lastname: Nieuwenhuyzen
authors.forename: Robert P
authors.initials: RP
authors.lastname: Doyle
mesh_terms: D002621:Chemistry / Q000379:methods*; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D011756:Diphosphates / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008670:Metals / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D011756:Diphosphates; D008024:Ligands; D008670:Metals; D014867:Water; D010758:Phosphorus; D009532:Nickel