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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.

The structural and magnetic properties of the tris-dithiooxalato salts, A[M I I Cr(C 2 S 2 O 2 ) 3 ], have been investigated with A + = PPh 4 +, N(n-C n H 2 + 1 ) 4 +, with n = 3-5, where M I I is Mn, Fe, Co, and Ni. With the exception of A[MnCr-(C 2 S 2 O 2 ) 3 ], all the salts are ferromagnets with Curie temperatures, T c , between 5 and 16 K. In contrast to the corresponding oxalates which are ferromagnetic, the A[MnCr(C 2 S 2 O 2 ) 3 ] compounds are paramagnetic above 2 K. Powder neutron diffraction studies of d 2 0 -PPh 4 [FeCr(C 2 S 2 O 2 ) 3 ] indicate that no structural phase transitions occur between 2.4 and 285 K and that the coefficient of linear expansion is four times larger for the c-axis than for the a-axis. The crystal structure refined from powder neutron diffraction data confirms the honeycomb layer arrangement observed in the related bimetallic tris-oxalate salts. The Mossbauer spectra reveal that the iron(II) in PPh 4 [FeCr-(C 2 S 2 O 2 ) 3 ] is coordinated mainly to six oxygen atoms of the dithiooxalato ligand but with a minor component of sulfur coordination that increases with aging of the sample; the iron(II) is high-spin in both cases. Powder neutron diffraction profiles of d 2 0 -PPh 4 (FeCr(C2S202) 3 ] below T c show magnetic intensity with a q = 0 propagation vector, confirming the presence of ferromagnetic order.

Synthesis, structure determination by single-crystal X-ray diffraction, and physical properties are reported and compared for superconducting and semiconducting molecular charge-transfer salts with stoichiometry (BEDT-TTF)(4)[A(I)M(III)(C(2)O(4))(3)].PhCN, where A(I) = H(3)O, NH(4), K; M(III) = Cr, Fe, Co, Al; BEDT-TTF = bis(ethylenedithio) tetrathiafulvalene. Attempts to substitute M(III) with Ti, Ru, Rh, or Gd are also described. New compounds with M = Co and Al are prepared and detailed structural comparisons are made across the whole series. Compounds with A = H(3)O(+) and M = Cr, Fe are monoclinic (space group C2/c), at 150, 120 K a = 10.240(1) A, 10.232(12) A; b = 19.965(1) A, 20.04(3) A; c = 34.905(1) A, 34.97(2) A; beta = 93.69(1) degrees, 93.25(11) degrees, respectively, both with Z = 4. These salts are metallic at room temperature, becoming superconducting at 5.5(5) or 8.5(5) K, respectively. A polymorph with A = H(3)O(+) and M = Cr is orthorhombic (Pbcn) with a = 10.371(2) A, b = 19.518(3) A, c = 35.646(3) A, and Z = 4 at 150 K. When A = NH(4)(+), M = Fe, Co, Al, the compounds are also orthorhombic (Pbcn), with a = 10.370(5) A, 10.340(1) A, 10.318(7) A; b = 19.588(12) A, 19.502(1) A, 19.460(4) A; c = 35.790(8) A, 35.768(1) A, 35.808(8) A at 150 K, respectively, with Z = 4. All of the Pbcn phases are semiconducting with activation energies between 0.15 and 0.22 eV. For those compounds which are thought to contain H(3)O(+), Raman spectroscopy or C=C and C-S bond lengths of the BEDT-TTF molecules confirm the presence of H(3)O(+) rather than H(2)O. In the monoclinic compounds the BEDT-TTF molecules adopt a beta' ' packing motif while in the orthorhombic phases (BEDT-TTF)(2) dimers are surrounded by monomers. Raman spectra and bond length analysis for the latter confirm that each molecule of the dimer has a charge of +1 while the remaining donors are neutral. All of the compounds contain approximately hexagonal honeycomb layers of [AM(C(2)O(4))(3)] and PhCN, with the solvent occupying a cavity bounded by [M(C(2)O(4))(3)](3-) and A. In the monoclinic series each layer contains one enantiomeric conformation of the chiral [M(C(2)O(4))(3)](3-) anions with alternate layers having opposite chirality, whereas in the orthorhombic series the enantiomers form chains within each layer. Analysis of the supramolecular organization at the interface between the cation and anion layers shows that this difference is responsible for the two different BEDT-TTF packing motifs, as a consequence of weak H-bonding interactions between the terminal ethylene groups in the donor and the [M(C(2)O(4))(3)](3-) oxygen atoms.

The new charge transfer salt, beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].C(5)H(5)N, I, (bedt-ttf = bis(ethylenedithio)tetrathiafulvalene) has a crystal structure closely similar to that of the reported salt beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].C(6)H(5)CN, II, which has a superconducting critical temperature of 8.6 K. However, variable temperature magnetic and transport experiments show that I has a metal to insulator transition at 116 K. The crystal structure of I has been determined above (150 K) and below (90 K) the metal to insulator transition and comparisons are made with the structure of II. The pyridine solvate crystallizes in the monoclinic space group C2/c with a = 10.267(2) Å, b = 19.845(4) Å, c = 34.907(7) Å, beta = 93.22(3) degrees, Z = 4 at 150 K and with a = 10.2557(15) Å, b = 19.818(28) Å, c = 34.801(49) Å, beta = 93.273(14) degrees, Z = 4 at 90 K. The structures of I and II both consist of layers of bedt-ttf with +0.5 formal charge per molecule and layers of approximately hexagonal symmetry containing H(3)O(+) and [Fe(C(2)O(4))(3)](3)(-). The solvent molecules occupy hexagonal cavities formed by the anionic layer. Changing the solvent molecule from C(6)H(5)CN to C(5)H(5)N induces disorder in the bedt-ttf layer which accounts for the dramatic difference in observed physical properties. For I, at 150 K, one-half of all the bedt-ttf molecules have identical conformations to all the molecules in II where both terminal ethylene groups of each bedt-ttf molecule are twisted and eclipsed with respect to the opposite end of the molecule. The remaining 50% of bedt-ttf molecules in I have disordered ethylene groups. The disorder persists at 90 K where it can be resolved into two conformations: twisted-twisted eclipsed and twisted-twisted staggered.

The magnetic structures of the layer molecular-based ferrimagnets P(C6D5)4MIIFe(C2O4)3 (MII = Mn, Fe) have been investigated by neutron powder diffraction. The magnetic order in the MnFe compound is best represented by the R3c Shubnikov group with moments aligned along the c axis. In the FeFe compound only one magnetic reflection [201] is observed, indicating incomplete long-range order at 5 K, but with moments also parallel to c.

N&MI1P04*H20 (MI1 = Mn, Fe, Co, Ni) and KM"PO4qH20 (MI1 = Mn, Co, Ni) have been prepared and characterized by X-ray powder diffraction and bulk magnetometry, and the corresponding deuterio compounds, by neutron powder diffraction. They are isomorphous (space group Pmn21). The divalent metal ions form approximately square-planar layers of comer-sharing octahedra, the layers being bound by hydrogen bonds in the ammonium compounds and by electrostatic interactions in the potassium ones. In all cases, the M"O6 octahedra are severely distorted, the point symmetry being C2". Bulk susceptibility measurements on NH4FeP04eH20, N&MnP04aH20, and KMnP04*H2O show they are weakly ferromagnetic, with Nee1 temperatures of TN = 24.0(2), 17.5(3), and 18.0(3) K, respectively. Powder neutron diffraction was used to determine the underlying antiferromagnetic component of the structures. All three materials have simple two-sublattice structures, with the antiferromagnetic moments along &[OlO], perpendicular to the plane of the metal-containing layers. Analysis using the irreducible representations of the space group shows that the ferromagnetic moments are parallel to [OOl].

The compound (BEDT-TTF)(4). Fe-2(C2O4)(5) consists of an Fe-(III)-F-(III) oxalate bridged dimer, with a Fe-Fe distance of 5.472 Angstrom interspersed with 4 BEDT-TTF in a "checkerboard" arrangement It contains [Fe-2(C2O4)(5)](4-) anions and four dimerized BEDT-TTF cations each having an approximate charge of +1. The compound is semiconducting and exhibits short-range antiferromagnetic ordering at low temperature.

The structural and magnetic properties of the tris-dithiooxalato salts, A[M(II)Cr(C(2)S(2)O(2))(3)], have been investigated with A(+) = PPh(4)(+), N(n-C(n)()H(2)(n)()(+1))(4)(+), with n = 3-5, where M(II) is Mn, Fe, Co, and Ni. With the exception of A[MnCr(C(2)S(2)O(2))(3)], all the salts are ferromagnets with Curie temperatures, T(c), between 5 and 16 K. In contrast to the corresponding oxalates which are ferromagnetic, the A[MnCr(C(2)S(2)O(2))(3)] compounds are paramagnetic above 2 K. Powder neutron diffraction studies of d(20)-PPh(4)[FeCr(C(2)S(2)O(2))(3)] indicate that no structural phase transitions occur between 2.4 and 285 K and that the coefficient of linear expansion is four times larger for the c-axis than for the a-axis. The crystal structure refined from powder neutron diffraction data confirms the honeycomb layer arrangement observed in the related bimetallic tris-oxalate salts. The Mössbauer spectra reveal that the iron(II) in PPh(4)[FeCr(C(2)S(2)O(2))(3)] is coordinated mainly to six oxygen atoms of the dithiooxalato ligand but with a minor component of sulfur coordination that increases with aging of the sample; the iron(II) is high-spin in both cases. Powder neutron diffraction profiles of d(20)-PPh(4)[FeCr(C(2)S(2)O(2))(3)] below T(c) show magnetic intensity with a q = 0 propagation vector, confirming the presence of ferromagnetic order.

The new charge-transfer salt β″-(BEDT-TTF)[(HO)Cr(CO )]S, where BEDT-TTF = bis-(ethylenedithio)tetrathiafulvalene and S = CHCl has a broad metal-insulator transition at approximately 150 K. This differs from similar salts in the BEDT-TTF tris(oxalato) metalate series, notably the superconducting materials with S = PhCN and the salt with S = CHN, which has a sharp metal-insulator transition.

Electrolytic oxidation of BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) in the presence of anionic rhenium thiocyanato complexes has led to the crystallization of two phases containing Re(2)(NCS)(10)(n)()(-) (n = 2, 3), while Re(NCS)(6)(2)(-) and Re(2)(NCS)(8)(2)(-) gave no characterizable products. (BEDT-TTF)(3)[Re(2)(NCS)(10)].2CH(2)Cl(2) (1) and (BEDT-TTF)(2)[Re(2)(NCS)(10)].C(6)H(5)CN (2) are both triclinic (Ponemacr;) with unit cell parameters a = 12.185(3) Å, b = 13.251(3) Å, c = 14.772(2) Å, alpha = 63.69(1) degrees, beta = 86.56(2) degrees, gamma = 64.50(2) degrees (Z = 1) and a = 13.730(4) Å, b = 14.882(4) Å, c = 16.588(4) Å, alpha = 75.98(2) degrees, beta = 85.63(2) degrees, gamma = 66.95(2) degrees (Z = 2), respectively. Both salts present packing arrangements of BEDT-TTF not found before. In compound 1 mixed layers of anions and cations contain no stacks of BEDT-TTF. In 2 there are layers of segregated anions and cations, the latter having their long axes nearly parallel to the layers. This compound is the first in which Re(2)(NCS)(10)(2)(-) has been structurally characterized. In both compounds there are numerous close S-S contacts between the NCS ligands and the BEDT-TTF. The compounds are semiconductors, the conductivity being attributed to low-dimensional hopping rather than coherent transport. The magnetic properties of 1 are modeled by a superposition of a Curie-Weiss contribution for the anion and a dimer contribution from the cation.

The synthesis and structural and magnetic characterization of 16 compounds AM(II)Fe(III)(C(2)O(4))(3) (A = N(n-C(3)H(7))(4), N(n-C(4)H(9))(4), N(n-C(5)H(11))(4), P(n-C(4)H(9))(4), P(C(6)H(5))(4), N(n-C(4)H(9))(3)(C(6)H(5)CH(2)), (C(6)H(5))(3)PNP(C(6)H(5))(3), As(C(6)H(5))(4); M(II) = Mn, Fe) are reported. X-ray powder diffraction profiles are indexed in R3c or its subgroup P6(5)22 or P6/mmm to derive unit cell constants. The structures of all the compounds consist of two-dimensional honeycomb networks [M(II)Fe(III)(C(2)O(4))(3)(-)](infinity). The M(II) = Fe compounds behave as ferrimagnets with T(c) between 33 and 48 K, but five exhibit a crossover from positive to negative magnetization near 30 K when cooled in a field of 10 mT. The compounds exhibiting this unusual magnetic behavior are those that have the highest T(c). Within the set N(n-C(n)()H(2)(n)()(+1))(4)Fe(II)Fe(III)(C(2)O(4))(3) (n = 3-5), T(c) increases with interlayer separation and the low-temperature magnetization changes from positive (n = 3) to negative (n = 4, 5). In the M = Mn(II) compounds, the in-plane cell parameter a(0) is approximately 0.03 Å greater than in the corresponding M = Fe(II) ones while the interlayer separation (c(0)/6) is on average 0.08 Å smaller. All members of the M(II) = Mn series have magnetic susceptibilities showing broad maxima at 55 K characteristic of two-dimensional antiferromagnetism, but the magnetization of several of the salts increases sharply below 27 K due to the onset of spin canting, the magnitude of which varies significantly with A.

The mixed-valence iron fluoride, Fe2F5.7H2O, has been investigated by a variety of techniques including Mossbauer and electronic spectroscopy and magnetic susceptibilities. The material is found to be a Class I mixed-valence complex, and is shown to contain discrete Fe(H2O)6(++) and FeF5(H2O)(--) ions. (Author)