Bulk spontaneous magnetization in the new radical cation salt TM-TTF[Cr(NCS)(4)(isoquinoline)(2)] (TM-TTF = tetramethyltetrathiafulvalene).
ABSTRACT A new organic-inorganic hybrid salt [TM-TTF][Cr(NCS)(4)(isoquinoline)(2)] (1) (TM-TTF = Tetramethyltetrathiafulvalene) has been synthesized. Compound 1 crystallizes in the triclinic P space group with a = 8.269(1), b = 10.211(2), and c = 11.176(2) A, alpha = 89.244(9), beta = 88.114(6), and gamma = 74.277(7) degrees, V = 907.6(3) A(3), and Z = 1. The crystal structure was resolved in the temperature range between 223 and 123 K, showing that changes in the crystal structure at low temperature result in stronger interactions between anions and cations. The packing of 1 consists of mixed anion-cation layers in the bc plane containing S.S and pi-pi anion-cation interactions, the layers being connected by very short S.S contacts between anions and cations. Magnetic measurements in a small external field show bulk spontaneous magnetization with a T(c) of 6.6 K consistent with the presence of weakly coupled ferrimagnetic order in compound 1. The EPR measurements also demonstrate the interaction between the d and pi electrons and the presence of an internal magnetic field brought about by the magnetic ordering.
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ABSTRACT: The 2 : 1 salts of a new donor molecule, benzotetrathiafulvalenothioquinone-1,3-dithiolemethide (Benzo-TTFVS) with magnetic FeCl4− and FeBr4− ions, and with non-magnetic GaCl4− and GaBr4− ions were obtained as single crystals by an electrochemical oxidation method. All of the crystals have very similar structures to each other, in which two different layers of the donor molecules and the counteranions are stacked alternately, although the separation distance between the neighboring donor layers in the FeCl4− and GaCl4− salts is shorter by 0.43–0.47 Å than that in the FeBr4− and GaBr4− salts. The donor molecules formed a β-like stacking structure with almost the same interplanar distances and effective overlaps along the stacking direction, such that these salts showed high electrical conductivities (9–33 S cm−1) at room temperature, as well as metallic behavior. However, owing to a quasi one-dimensional character of the calculated band structures, a transition of metal-to-semiconductor with a very small activation energy of <30 meV occurred at comparatively high temperatures of 100–150 K. The Fe(III) d spins of the FeCl4− ions were subject to weakly antiferromagnetic interaction (Weiss temperature, θ = −4.3 K). While, the interaction between the Fe(III) d spins of the FeBr4− ions was fairly strong (θ = −16.1 K), eventually giving rise to an antiferromagnetic ordering at the temperature of 5.8 K. In the magnetization measurement of the FeBr4− salt up to 320 kOe at 0.5 K, a spin-flop occurred near 20 kOe and a saturation near 156 kOe.Journal of Materials Chemistry 01/2005; 15(34). · 5.97 Impact Factor
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ABSTRACT: A charge-transfer compound [(CH3)3CNH3]3[PMo12O40] · 2H2O was synthesized and characterized by IR, UV, ESR, diffusion reflectance electronic spectrum, cyclic voltammogram and X-ray crystallography. Oxygen atoms of the polyoxometalate anion, N atoms of organic substrates (CH3)3CNH2 and O atoms of water molecules are involved in hydrogen bonding. The solid reflectance electronic spectra and IR data indicate the presence of interaction between the [PMo12O40]3− and the organic substrates in the solid state. Photosensitivity to ultraviolet light was assessed for the compound, showing that charge-transfer resulted from oxidation of the organic substrates and the reduction of the heteropolyanion.Transition Metal Chemistry 01/2006; 31(6). · 1.40 Impact Factor