Synthesis and structural and magnetic characterization of {[(phen) 2Ni]2(μ-P2O7)}·27H 2O and {[(phen)2Mn]2(μ-P2O 7)}·13H2O: Rare examples of coordination complexes with the pyrophosphate ligand

Oluwatayo F. Ikotun, N. Gabriel Armatus, Miguel Julve, Paul E. Kruger, Francesc Lloret, Mark Nieuwenhuyzen, Robert P. Doyle

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


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(μ-P2O7)}·27H2O (1) and {[(phen)2Mn]2(μ-P2O7)}·13H 2O (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 Å in 1 and 4.700 Å in 2, and its conformation also gives rise to an intramolecular π-π interaction between two adjacent phen ligands. Intermolecular π-π 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 = -JS A·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.

Original languageEnglish (US)
Pages (from-to)6668-6674
Number of pages7
JournalInorganic Chemistry
Issue number16
StatePublished - Aug 6 2007

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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