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The magnetic properties of a microcrystalline powder sample of Cr[(CH3PO3)(H2O)] have been investigated by means of dc magnetization and ac magnetic susceptibility measurements as a function of temperature, frequency and magnetic field. The magnetic measurements show the presence of a long range ordering with an hysteretic behaviour below the critical temperature TN of 40 K, which is a relatively high temperature for this class of molecule based magnets.1 The isothermal magnetization recorded at several temperatures below TN are typical of a canted antiferromagnet.2 More interesting, an analysis of the ac magnetic susceptibility vs. temperature plot reveals in the temperature region 34-40 K the presence of several features both in the ?' and ?" curves, whose nature is under investigation and will be presented and discussed. References 1)C. Bellitto in J.S. Miller and M. Drillon (Eds) Magnetism: Molecules to Materials, Wiley-VCH, Weinheim, 2001, vol. 2, 425-456. 2)C. Bellitto, F. Federici, S.A. Ibrahim, Chem.Com. 1996,759-760.

Two new layered metal(II) bis-phosphonates have been prepared by chemical assembling of a functional organic ligand with paramagnetic transition metal ions. The ligand is represented by the bifunctional R(PO3H2)2 molecule where R is the N,N'-bis(2-phosphonoethyl)perylene-3,4;9,10-tetracarboximide (hereafter PDI-BP). The latter features an extended ?- electron system, which is responsible of interesting optical properties. The PDI-BP ligand reacts with Mn(II) and Ni(II) ions to give the new metal(II) bisphosphonates of formula Mn2[(PDI-BP)(H2O)2]·0.5H2O (1) and Ni2[(PDIBP)( H2O)2]·3H2O (2). The compounds were characterized by several techniques and resulted to be scarcely crystalline red solids. The magnetic properties of both the compounds have been explored by a SQUID magnetometer in the temperature range from r. t. down to 2 K. Magnetic measurements were performed in the DC and AC modes as a function of temperature and magnetic field. The experiments in the high temperature region confirm the electronic spin configurations (d5(S = 5/2) for Mn(II) ion and d8(S = 1) for Ni(II) ion), respectively. At low temperatures, DC susceptibility vs. T measurements on compound (1) indicate the presence of antiferromagnetic coupling and AC susceptibility experiments show two peaks in the in-phase and out-of-phase signals located at 2.5 K and 25 K. The slightly frequency dependent signal at lower temperatures might be attributed to domain wall movements in the ordered state, while the frequency dependent peak at higher temperatures may be due to disorder in the Mn(II) layer. Hysteresis cycles performed below 30 K indicate the presence of spin canting below that temperature.The magnetic behavior of compound (2) is similar to the previous one. AC susceptibility measurement vs. T shows a peak located at ca. 20 K, in both, the in-phase ?' and out-of phase ?'' components of the AC susceptibility. The signals are sligthly frequency dependent, and probably associated to disorder in the Ni(II) layer. Hysteresis loops recorded at several temperatures below 20 K together with the previous data are the signature of magnetic order.

cited By 2; International audience; Reactions of the [FeIII(CN)6]3- anion with the [CuII(tn)]2+ ion (tn = 1,3-diaminopropane) afford the compounds [CuII(tn)]2[FeII(CN) 6]3·[Na3FeIII(CN) 6]·12H2O (1) and [Cun(tn)] 2[FeII(CN)6]·KCl·5H 2O (2). Despite the differences concerning their asymmetric units, both structures present strong similar features: in both structures, the Cu(II) ion presents a square-base pyramidal CuN5 environment and each [FeII(CN)6]4- anion is linked to six Cu(II) ions through its six N atoms leading to infinite [CuII(tn)] 2[FeII(CN)6] layers which can be viewed as 2-D layered arrangement generated by the defective cubane units Cu 4Fe3 involving Fe-CN-Cu bridges. The most important differences between the two structures concern essentially the inter-layer arrangement which is occupied, in compound 1, by isolated paramagnetic [Fe(CN)6]3- anions and water molecules, while in compound 2, this interlayer space is occupied by K+, Cl- ions and water molecules. Magnetic data indicate for 1 weak antiferromagnetic interactions and presence of magnetically isolated [FeIII(CN) 6]3-anion and for 2 weak ferromagnetic interactions between the Cu(II) ions. © 2005 Elsevier B.V. All rights reserved.

cited By 32; International audience; A new polynuclear copper(II) complex [Cu7(OH)6Cl2-(pn) 6(H2O)2](C(CN)3)4Cl 2 with hydroxo-bridging ligands has been prepared; the centrosymmetric cluster cation can be described as two Cu4O3Cl distorted cubane units sharing one copper cation.

cited By 19; International audience; Electrochemical combination of the magnetic dinuclear anion [MM′(C2O4)(NCS)8]4- (MM′ = CrIIICrIII, CrIIIFeIII) with the ET organic π-donor (ET = BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) gives rise to two new isostructural molecular hybrid salts ET5[MM′(C2O4)(NCS)8], with MM′ = CrCr (1), CrFe (2). The molecular structure of compound 1 has been determined by single crystal X-ray diffraction. The particular arrangement of the organic units consists of an unprecedented two-dimensional organic sublattice nearly similar to that observed in κ-phase structures. For both compounds, the magnetic susceptibility measurements indicate (i) the ET radicals do not contribute to the magnetic moment probably due to the presence of strong antiferromagnetic interaction between them, and (ii) in the anion, the magnetic coupling is antiferromagnetic for 1 (J = -3.65 cm-1) and ferromagnetic for 2 (J = 1.14 cm-1, J being the parameter of the exchange Hamiltonian H = -2JS1S2). The field dependence of the magnetization of compound 2 at 2.0 K gives further evidence of the S = 4 ground-state arising from the interaction between S = 3/2 Cr(III) and S = 5/2 Fe(III). EPR measurements confirm the nature of the magnetic interactions and the absence of any contribution from the organic part, as observed from the static magnetic measurement. Conductivity measurements and electronic band structure calculations show that both salts are semiconductors with low activation energies.