Synthesis, structure and properties of [ethylpyridinium][Ni(mnt)2]: evidence for an unusual magnetically ordered ground state

[Ethylpyridinium][Ni(mnt) 2 ] has been prepared by electrochemical oxidation of the corresponding dianionic salt. The X-ray structure has been determined. Three different environments were observed for the paramagnetic anions with two in a stacking mode and one approximately orthogonal to the stack. The stacking showed an ACA-type repeat unit with an inversion centre on complex C. Magnetic susceptibility measurements show Curie-Weiss behaviour with a change in parameters at around 50 K. Above this temperature a Curie constant of 0.3 emu K mol –1 and a Weiss constant of –150 K were observed and below 50 K these values were 0.08 emu K mol –1 and +2 K respectively. A maximum in the susceptibility was observed at 285 mK which suggests low temperature ordering to a phase with a non-cancelled alignment of the spins. Intermolecular interactions and the effect of temperature were assessed in terms of transfer integral calculations.

[1]  Kentaro Suzuki,et al.  Magnetism of a Two-Dimensional Weak-Ferromagnetic Organic Radical Crystal, 1,3,5-Triphenyl-6-Oxoverdazyl , 1997 .

[2]  J. Rawson,et al.  Spontaneous Magnetization in a Sulfur–Nitrogen Radical at 36 K , 1996 .

[3]  David A. Fletcher,et al.  The United Kingdom Chemical Database Service , 1996, J. Chem. Inf. Comput. Sci..

[4]  R. Friend,et al.  Intermolecular interactions in the molecular ferromagnetic NH4Ni(mnt)2· H2O , 1996, Nature.

[5]  R. Friend,et al.  Single Crystal Magnetic Measurements of the Molecular Magnet NH4Ni(mnt)2.H2O , 1995 .

[6]  R. Friend,et al.  Structure and Physical Properties of the Tetraphenylphosphonium-[Ni(dmit)2]3 (dmit = 2-thioxo-1,3-dithiol-4,5-dithiolate) Salt , 1995 .

[7]  A. Underhill,et al.  Molecular metals and superconductors derived from metal complexes of 1,3-dithiol-2-thione-4,5-dithiolate (dmit) , 1991 .

[8]  P. I. Clemenson.  The chemistry and solid state properties of nickel, palladium and platinum bis(maleonitriledithiolate) compounds , 1990 .

[9]  H. Kisch,et al.  Charge‐Transfer‐Komplexe von Metalldithiolenen, IV. Viologene als redoxaktive Akzeptoren – Synthese und elektrische Leitfähigkeit , 1989 .

[10]  W. Reith,et al.  Synthesis and Structure of (ET)[Ni{SC(CN)C(CN)S}2], a Radical Cation Salt of Bis(ethylenedithio)tetrathiafulvalene† , 1988 .

[11]  A. Underhill,et al.  Preparation, structure and properties of [Ni(S2C2(CN)2)2]− salts with small cations , 1987 .

[12]  A. Underhill,et al.  Structure and properties of [M(S2C2(CN)2)2] (where M is Ni, Pd, or Pt) monoanions with small cations , 1986 .

[13]  P. Manoharan,et al.  Structural and magnetic investigations on the CT ion-radical salt [p-(dimethylamino)phenyl]dimethylammonium bis(maleonitriledithiolato)nickelate(III) , 1983 .

[14]  P. Manoharan,et al.  Exchange interactions in tropylium bis(1,2‐dicyanoethylene dithiolato) nickelate (III) , 1981 .

[15]  L. R. Melby,et al.  1,2-Dicyanoethylene-1,2-dithiolate Chelates , 1964 .

[16]  H. Gray,et al.  A Spin-Free Square Planar Cobaltous Complex , 1962 .