Ferromagnetic Coupling in “Double-Bridged” Dihydrogenpyrophosphate Complexes of Cobalt(II) and Nickel(II)

Abstract

Three isostructural compounds of the formula {[M(bipy)(H2O)(H2P2O7)]2·2H2O} [bipy = 2,2'-bipyridine; M = Ni (1), Co (2), Mn (3)] have been isolated from aqueous solutions containing the corresponding metal(II) chloride hydrate with a bipy and sodium pyrophosphate solution in a 1:1:2 molar ratio, and their structures were determined by single-crystal X-ray diffraction. The structures of 1-3 consist of neutral aqua(2,2'-bipyridine)metal(II) dinuclear units bridged by two dihydrogenpyrophosphate groups adopting a bidentate/monodentate mode. Each metal ion in 1-3 is six-coordinate in a distorted octahedral geometry, with the reduced value of the angle subtended by the chelating bipy at the metal ion [79.6(1)° (1), 77.32(7)° (2), and 72.9(1)° (3)] being the main source of this distortion. The values of the intramolecular metal-metal separation are 5.271(1) Å (1), 5.3065(8) Å (2), and 5.371(1) Å (3). Magnetic susceptibility measurements on polycrystalline samples of 1-3 in the temperature range 1.9-300 K shows weak intramolecular ferromagnetic [J = +1.86(2) cm(-1) (1) and +0.25(1) cm(-1) (2)] and antiferromagnetic [J = -0.48(1) cm(-1) (3)] coupling, with the spin Hamiltonian being defined as H = -JSM1·SM1a. This rarely observed coordination mode for dihydrogenpyrophosphate leads to ferromagnetic coupling in complexes of nickel(II) or cobalt(II).

Polymorphic Derivatives of NiII and CoII Mesocates with 3D Networks and “Brick and Mortar” Structures: Preparation, Structural Characterization, and Cryomagnetic Investigation of New Single-Molecule Magnets

“…The calculated curve (black solid line in Figure ) reproduces quite well the magnetic data over the whole temperature range investigated. The values of α, λ and Δ obtained by a fit are within the range of those reported for high-spin octahedral cobalt­(II) ions. − …”

Host–Guest Chemistry: Oxoanion Recognition Based on Combined Charge‐Assisted C−H or Halogen‐Bonding Interactions and Anion⋅⋅⋅Anion Interactions Mediated by Hydrogen Bonds

“…[42] 2) The crystallization solvent is am ixture of acetonitrile/methanol, and consequently,i ti se xpected that under the recrystallization conditions the HP 2 O 7 3À anion induces deprotonation of methanolt og ive H 2 P 2 O 7 2À .3 )Recently,t he capability of the H 2 P 2 O 7 2À anion to form dimeric complexes has been described. [43] 4) Supportf or parts of these assumptions is given by previous, related results, in which ar ecognition process of calix[4]pyrrole-basedr eceptors and HP 2 O 7 3À ,a sa nalytes in aqueous media, provided the corresponding H 2 P 2 O 7 2À complexes. [44] The structure of compound [8 2 + ][SO 4 ] 0.5 [BF 4 ]w as also determined by single-crystal XRD (Figure 6).…”

Coordination Patterns of the Diphosphate in IDP Coordination Complexes: Crystal Structure and Chirality

“…The metal-binding patterns of PP i salts and their properties in diverse areas such as catalysis, magnetism, materials, biology, etc., have been a source of considerable research efforts in recent years . The phosphate group as a part of nucleotides can polymerize in nucleic acids and occur as intermediates and coenzymes. − The great majority of the diphosphate coordination complexes reported to date contained only single PP i units or multiple bridging PP i units . The coordination pattern of the PP i unit in nucleotide complexes has not been explored systematically to date, expect for a few crystal structures of adenosine and uridine polyphosphate complexes in the Cambridge Structural Database.…”