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Research has been conducted on the coordinate complexes. The reaction of M{N(SiMe (sub)3) (sub)2} (sub)2 (M= Mn, Re, Co) with different beta-diketimines has produced three-coordinate complexes characterized via magnetic measurements, X-ray crystallography and NMR and IR spectroscopy and the details are included.

A new rare earth metal Zintl phase, Eu3In2P4 is synthesized by utilizing a metal flux method. At the magnetic ordering temperature, this compound shows a negative magnetoresistance and there are two crystallographically different Eu(super 2) sites in this compound.

Eu3InP3 is prepared as large single crystals with an indium flux reaction. The temperature dependence of the conductivity indicates that Eu3InP3 is a small band gap semiconductor.

Research has been conducted on transitio-metal-containing Zintl compound Eu (sub)10 Mn (sub)6 Sb (sub)13. The authors describe the preparation of this compound via high-temperature tin-flux synthesis, and report that its structure has been investigated via the use of single-crystal X-ray diffraction.

Large, high quality single crystals of a new Zintl phase, Euln2As2, have been synthesized from a reactive indium flux. Euln2As2 is isostructural to the recently reported phase Euln2P2, and it is only the second reported member of the group of compounds with formula AM2X2 (A = alkali, alkaline earth, or rare earth cation; M = transition or post-transition metal; and X = Group 14 or 15 element) that crystallizes in the hexagonal space group P63/mmc (a = 4.2067(3) Å, c = 17.889(2) Å and Z = 2). The structure type contains layers of A2+ cations separated by [M2X2]2- layers along the crystallographic c-axis. Crystals of the title compound were mounted for magnetic measurements, with the crystallographic c-axis oriented either parallel or perpendicular to the direction of the applied field. The collective magnetization versus temperature and field data indicate two magnetic exchange interactions near 16 K, one involving Eu2+ … Eu2+ intralayer coupling and the other involving Eu2+ …. Eu2+ coupling between layers. Euln2As2 is metallic and magnetoresistive, as is the isostructural phosphide, and both compounds have coincident resistivity and magnetic ordering transitions, consistent with the observation of colossal magnetoresistance. Negative colossal magnetoresistance (MR = {[ρ(H) - ρ(0)/ρ(H) x 100% of up to -143% (at T = 17.5 K, H = 5 T) is Observed for Euln2As2, approximately half of that observed for the more resistive phosphide, which has a higher magnetic ordering temperature and local moment coupling strength. [ABSTRACT FROM AUTHOR]

Single-crystalline samples of a new Zintl compound, Eu3Ga2P4, have been synthesized by a Ga-flux method. Eu3Ga2P4 is found to crystallize in a monoclinic unit cell, space group C2/c, isostructural to Ca3Al2As4. The structure is composed of a pair of edge-shared GaP4 tetrahedra, which link by corner-sharing to form Ga2P4 two-dimensional layers, separated by Eu2+ ions. Magnetic susceptibility showed a Curie-Weiss behavior with an effective magnetic moment consistent with the value for Eu2+ magnetic ions. Below 15 K, ferromagnetic ordering was observed and the saturation magnetic moment was 6.6 μB. Electrical resistivity measurements on a single crystal showed semiconducting behavior. Resistivity in the temperature range between 280 and 300 K was fit by an activation model with an energy gap of 0.552(2) eV. The temperature dependence of the resistivity is better described by the variable-range-hopping model for a three-dimensional conductivity, suggesting that Eu-P bonds are involved in the conductivity. A large magnetoresistance, up to −30%, is observed with a magnetic field H = 2 T at T = 100 K, suggesting strong coupling of carriers with the Eu2+ magnetic moment. [ABSTRACT FROM AUTHOR]

A new rare earth metal Zintl phase, Eu3In2P4, was synthesized by utilizing a metal flux method. The compound crystallizes in the orthorhombic space group Pnnm with the cell parameters a = 16.097(3) Å, b = 6.6992(13) Å, c = 4.2712(9) Å, and Z = 2 (T= 90(2) K, R1 = 0.0159, wR2 = 0.0418 for all data). It is isostructural to Sr3In2P4. The structure consists of tetrahedral dimers, [In2P2P4/2]6-, that form a one-dimensional chain along the c axis. Three europium atoms interact via a Eu-Eu distance of 3.7401(6) Å to form a straight line triplet. Single-crystal magnetic measurements show anisotropy at 30 K and a magnetic transition at 14.5 K. High-temperature data give a positive Weiss constant, which suggests ferromagnetism, while the shape of susceptibility curves (χ vs T) suggests antiferromagnetism. Heat capacity shows a magnetic transition at 14.5 K that is suppressed with field. This compound is a semiconductor according to the temperature-dependent resistivity measurements with a room-temperature resistivity of 0.005(1) Ω m and Eg = 0.452(4) eV. It shows negative magnetoresistance below the magnetic ordering temperature. The maximum magnetoresistance (Δ ρ/ ρ (H)) is 30% at 2 K with H = 5 T. [ABSTRACT FROM AUTHOR]

Single-crystalline samples of a new Zintl compound, Eu(3)Ga(2)P(4), have been synthesized by a Ga-flux method. Eu(3)Ga(2)P(4) is found to crystallize in a monoclinic unit cell, space group C2/c, isostructural to Ca(3)Al(2)As(4). The structure is composed of a pair of edge-shared GaP(4) tetrahedra, which link by corner-sharing to form Ga(2)P(4) two-dimensional layers, separated by Eu(2+) ions. Magnetic susceptibility showed a Curie-Weiss behavior with an effective magnetic moment consistent with the value for Eu(2+) magnetic ions. Below 15 K, ferromagnetic ordering was observed and the saturation magnetic moment was 6.6 μ(B). Electrical resistivity measurements on a single crystal showed semiconducting behavior. Resistivity in the temperature range between 280 and 300 K was fit by an activation model with an energy gap of 0.552(2) eV. The temperature dependence of the resistivity is better described by the variable-range-hopping model for a three-dimensional conductivity, suggesting that Eu-P bonds are involved in the conductivity. A large magnetoresistance, up to -30%, is observed with a magnetic field H = 2 T at T = 100 K, suggesting strong coupling of carriers with the Eu(2+) magnetic moment.

Eu3InP3 has been prepared as large single crystals with an indium flux reaction. The structure of the new compound is isotypic to Sr3InP3 and crystallizes in the orthorhombic space group Pnma with unit cell dimensions of a = 12.6517(15) A, b = 4.2683(5) A, and c = 13.5643(14) A (Z = 4, T = 140 K, R1 = 0.0404, wR2 = 0.0971 for all data). The structure consists of one-dimensional chains of corner-shared distorted [InP2P2/2]6- tetrahedra separated by rows of Eu2+ ions. Two of the three crystallographically distinct europium sites have a short Eu(1)-Eu(2) distance of 3.5954(7) A, which yields Eu-Eu dimers. The Eu-P bond distances range from 2.974(2) to 3.166(2) A. The temperature dependence of the conductivity indicates that Eu3InP3 is a small band gap semiconductor. Both magnetization and Eu-151 Mossbauer spectral measurements indicate that the europium in Eu3InP3 is divalent and that at least two magnetic transitions occur. Magnetization studies reveal magnetic transitions at 14, 10.4, and approximately 5 K. These transitions are also observed in heat capacity studies of Eu3InP3. The Mossbauer spectra indicate that the two europium sites are ordered at 12 K and that all three europium sites are ordered at 8 K.

A new transition-metal-containing Zintl compound, Eu(10)Mn(6)Sb(13), was prepared by a high-temperature Sn-flux synthesis. The structure was determined by single-crystal X-ray diffraction. Eu(10)Mn(6)Sb(13) crystallizes in the monoclinic space group C2/m with a = 15.1791(6) A, b = 19.1919(7) A, c = 12.2679(4) A, beta = 108.078(1)*, Z = 4 (R1 = 0.0410, wR2 = 0.0920), and T = 90(2) K. The structure of Eu(10)Mn(6)Sb(13) is composed of double layers of Mn-centered tetrahedra separated by Eu(2+) cations. The double layers are composed of edge- and corner-sharing Mn-centered tetrahedra which form cavities occupied by Eu(2+) cations and [Sb(2)](4-) dumbbells. Linear [Sb(3)](5-) trimers bridging two tetrahedra across the cavity are also present. Bulk susceptibility data indicate paramagnetic behavior with a ferromagnetic component present below 60 K. Temperature-dependent electrical resistivity measurements show semiconducting behavior above 60 K (E(a)() = 0.115(2) eV), a large and unusually sharp maximum in the resistivity at approximately 40 K, and metallic behavior below 40 K. (151)Eu Mössbauer spectra confirm that the europium is divalent with an average isomer shift of -11.2(1) mm/s at 100 K; the spectra obtained below 40 K reveal magnetic ordering of six of the seven europium sublattices and, at 4.2 K, complete ordering of the seven europium sublattices.