J.R. Galán-Mascarós

Hybrid Molecular Magnets Obtained by Insertion of Decamethylmetallocenium Cations into Layered, Bimetallic Oxalate Complexes: [ZIIICp*2][MIIMIII(ox)3] (ZIII=Co, Fe; MIII=Cr, Fe; MII=Mn, Fe, Co, Cu, Zn; ox=oxalate; Cp*=pentamethylcyclopentadienyl)

A new series of hybrid organometallic - inorganic layered magnets with the formula [Z(III)Cp*2][M(II)M(III)(ox)3] (Z(III) = Co, Fe; M(III) = Cr, Fe; M(II) = Mn, Fe, Co, Cu, Zn; ox = oxalate; Cp* = pentamethylcyclopentadienyl) has been prepared. All of these compounds are isostructural and crystallize in the monoclinic space group C2/m, as found by X-ray structure analysis. Their structure consists of an eclipsed stacking of the bimetallic oxalate-based extended layers separated by layers of organometallic cations. These salts show spontaneous magnetization below To, which corresponds to the presence of ferro-, ferri-, or canted antiferromagnetism. Compounds in which the paramagnetic deca-methylferrocenium is used instead of the diamagnetic decamethylcobaltocenium are good examples of chemically constructed magnetic multilayers with alternating ferromagnetic and paramagnetic layers. The physical properties of this series have been thoroughly studied by means of magnetic measurements and ESR and Mossbauer spectroscopy. We have found that the two layers are electronically quasiindependent. As a consequence, the bulk properties of these magnets have not been significantly affected by the insertion of a paramagnetic layer of S = 1/2 spins in between the extended layers. In fact, the critical temperatures remain unchanged even when comparing [MCp*2]+ derivatives with [XR4]+ compounds (X = N, P; R = Ph, nPr, nBu). Nevertheless, the presence of the paramagnetic layer has been shown to have some influence on the hysteresis loops of these compounds. In the same context, the spin polarization of the paramagnetic units (which arises from the internal magnetic field created by the bimetallic layers in the ordered state) has been observed by Mossbauer and ESR spectroscopy.

Multifunctionality in hybrid molecular materials: Design of ferromagnetic molecular metals

Here we report recent advances in connection with the design, crystal structures and physical properties of novel hybrid organic-inorganic molecular materials combining ferromagnetic bimetallic oxalato-based networks and organic radicals of the tetrathiafulvalene (TTF) family, including the selenium and oxygen analogs.

Bimetallic cyanide-bridged complexes based on the photochromic nitroprusside anion and paramagnetic metal complexes

The synthesis, crystal structure, and physical characterization of the coordination compounds [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]x5H2O (1), [Ni(en)2][Fe(CN)5NO]x3H2O (2), [Mn(3-MeOsalen)(H2O)]2[Fe(CN)5NO] (3), and [Mn(5-Brsalen)]2[Fe(CN)5NO] (4) are presented. 1 crystallizes in the monoclinic space group P2(1)/n (a = 7.407(4) A, b = 28.963(6) A, c = 14.744(5) A, alpha = 90 degrees, beta = 103.26(4) degrees, gamma = 90 degrees, Z = 2). Its structure consists of branched linear chains formed by cis-[Ni(en)2]2+ cations and ferrocyanide and nitroprusside anions. The presence of two kinds of iron(II) sites has been demonstrated by Mössbauer spectroscopy. 2 crystallizes in the monoclinic space group P2(1)/c (a = 11.076(3) A, b = 10.983(2) A, c = 17.018(5) A, alpha = 90 degrees, beta = 107.25(2) degrees, gamma = 90 degrees, Z = 4). Its structure consists of zigzag chains formed by an alternated array of cis-[Ni(en)2]2+ cations and nitroprusside anions. 3 crystallizes in the triclinic space group P1 (a = 8.896(5) A, b = 10.430(5) A, c = 12.699(5) A, alpha = 71.110(5) degrees, beta = 79.990(5) degrees, gamma = 89.470(5) degrees, Z = 1). Its structure comprises neutral trinuclear bimetallic complexes in which a central [Fe(CN)5NO]2- anion is linked to two [Mn(3-MeOsalen)]+ cations. 4 crystallizes in the tetragonal space group P4/ncc (a = 13.630(5) A, c = 21.420(8) A, Z = 4). Its structure shows an extended 2D neutral network formed by cyclic octameric [-Mn-NC-Fe-CN-]4 units. The magnetic properties of these compounds indicate the presence of quasi-isolated paramagnetic Ni2+ and Mn3+. Irradiated samples of the four compounds have been studied by differential scanning calorimetry to detect the existence of the long-lived metastable states of nitroprusside.

Hybrid molecular materials based on organic molecules and the inorganic magnetic cluster [M4(H2O)2(PW9O34)2]10–(M2+=Co, Mn)

The synthesis and physical characterization of new organic–inorganic hybrids formed by conducting and magnetic networks are reported. The crystalline radical salts are formed by BEDT-TTF type donors as the organic part, and by large metal–oxide clusters of the type [M4(H2O)2(PW9O34)2 ]10– (M2+=Co, Mn) as the inorganic part. We also show how these magnetic clusters can be incorporated in conducting organic polymers to give hybrid organic–inorganic films.

Multifunctionality in hybrid molecular materials: design of ferromagnetic molecular metals and hybrid magnets

We report on the synthesis and physical properties of novel hybrid organic–inorganic molecular materials combining ferromagnetic bimetallic oxalato-based networks and functional organic molecules as the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) or cationic nitroxide free radicals. # 2002 Elsevier Science B.V. All rights reserved.

Magnetic conductors. Current approaches and achievements

Abstract The recent achievements of our group in the synthesis of molecular and polymeric materials combining conductivity and magnetism are presented. These results will be grouped in three main areas: (1) molecular magnetic conductors based upon TTF-type donors and discrete metal complexes and clusters (metal halides, metal cyanides, metal oxalates, polyoxometalate clusters,…), (2) conducting molecular ferromagnets based upon extended magnetic layers incorporating donors in between the inorganic layers and (3) conducting polymers incorporating magnetic complexes and clusters.

Hybrid molecular materials having conducting and magnetic networks: Charge transfer salts based on organic π-donor molecules and inorganic magnetic clusters.

Abstract The synthesis and physical characterization of new organic-inorganic hybrids formed by conducting and magnetic networks are reported. The crystalline radical salts are formed by BEDT-TTF type donors as conducting component, and by large metaloxide clusters of variable sizes and shapes (polyoxometalates) as magnetic component. We also show how these magnetic clusters can be incorporated in conducting organic polymers to give hybrid organic/inorganic films.

A new approach for the synthesis of magnetic materials based on nitroxide free radicals and inorganic coordination polymers

The use of nitronyl nitroxide (NN) radicals as spectators inside extended inorganic magnetic lattices is described. Two possibilities are presently being explored, namely, the design of oxalato-bridged bimetallic networks by using cationic NN radicals of the N-alkylpyridinium type as templating agents, and the design of bimetallic lattices based on hexacyanometalates and nickel(II) diaminocomplexes incorporating anionic NN radicals of the carboxyphenyl type.

Radical cation salts based on BEDT-TTF and the paramagnetic anion [Cr(NCS)6]3-

Abstract A new radical cation salt formulated as (ET)5.5[Cr(NCS)6] (ET = BEDT-TTF = bis(ethylene)dithiotetrathiafulvalene) has been synthesised and characterised by X-ray diffraction and magnetic measurements. The structure shows the presence of alternating layers of the ET units and mixed layers of anions and an isolated ET molecule. The magnetic susceptibility data in the temperature range 2–300 K show a Curie law with C = 1.771 cm3.K.mol−1 and Nα = 1.20.10−5 cm3.mol−1, in agreement with the presence of isolated Cr(III) without any contribution from the organic part.

π-facial interactions between Cl− and [S4N3]+. X-ray crystal structure of [S4N3]Cl

Abstract The X-ray structure of [S 4 N 3 ]Cl reveals three independent molecules, which all display π-facial interactions between the Cl − and the pseudo-aromatic [S 4 N 3 ] + rings to produce a structure containing “inverse sandwich” systems.