David P. Goshorn

Crystal structure and magnetic properties of a new molybdenophosphate: AgMo5P8O33

Abstract The crystal structure of AgMo5P8O33 has been determined from single-crystal X-ray diffraction data. AgMo5P8O33 crystallizes in the monoclinic space group I2 a (#15) with a = 23.050(8), b = 4.831(4), c = 22.935(9), A, β = 90.42(5)°, V = 2554(4), A3, Z = 4, R = 0.086 (Rw = 0.089) for 879 reflections with F2o > 3.0σ(F2o). The structure consists of large tunnels where the silver atoms are located. The framework is built up from MoO6 octahedra and P2O7 groups. The connectivity formula for AgMo5P8O33 is Ag(MoO 1 1 O 4 2 )(MoO 1 1 O 5 2 ) 4 (P 2 O 1 1 O 6 2 ) 4 . Powder magnetic susceptibility data confirm the presence of Mo5+ (d1) ions with spin 1 2 , and a featureless antiferromagnetic ordering appears to occur below 2.5 K. Magnetization isotherms at 1.3 and 4.2 K in magnetic fields up to 65 kG are reported. The lithium, sodium, calcium, strontium, barium, and lead analogs of AgMo5P8O33 were also prepared.

Synthesis and crystal structures of two thallium vanadium phosphates: TIVO2(HPO4) and TI3V2O3(VO)(PO4)2(HPO4)

Abstract Two thallium vanadium phosphate compounds have been crystallized hydrothermally and their structures determined by single-crystal X-ray diffraction. The first, a hydrogen phosphate containing only vanadium(V), crystallizes at 450°C and is orthorhombic, space group Pbca, with a = 9.257(2) A, b = 17.518(4) A, and c = 6.810(2) A; V = 1104.4(5) A3; Z = 8; Dx = 4.610 g/cm3; R = 0.048; and Rw = 0.048 for 564 independent observed reflections with I ≥ 3σ(I). The structure can be described as chains of corner-sharing distorted square pyramids. Adjacent square pyramids are bridged by the phosphate groups. The chains are linked together by hydrogen bonds to form puckered layers stacked along the b axis. The thallium(I) atoms are approximately 7-coordinated by oxygen atoms in sites between the layers. The compound is isostructural with the MVO2(HPO4) (M = K, Rb, and NH4) compounds whose structures were recently determined by powder X-ray diffraction (1). The second compound, prepared at 200°C, has the composition Tl3V2O3(VO)(PO4)2(HPO4) and contains both V(V) and V(IV). The structure is orthorhombic, space group Pnma, with a = 7.160(2) A, b = 13.378(2) A, and c = 14.422(1)A; V = 1381.4(7) A3; Z = 4; Dx = 5.378 g/cm3; R = 0.041; and Rw = 0.054 for 1093 independent observed reflections with I ≥ 3σ(I). The structure contains vanadium atoms in two independent sites. The vanadium atom V2 is octahedrally coordinated by six oxygen atoms and forms a OVOVOchain of composition VO(PO4)2 along the crystallographic a direction. The second vanadium atom (V1) is coordinated by five oxygen atoms in a square pyramidal arrangement and is found as a dimeric unit with composition V2O3(HPO4). The two different units are joined to form the complete vanadium phosphate framework structure by sharing the oxygen atoms of one phosphate group. Bond valence calculations indicate that the vanadium atom in the chain is V4+ and that the dimer contains equal amounts of V4+ and V5+. The two thallium atoms occupy distorted 8-coordinate sites in the framework.

Hydrothermal synthesis and characterization of vanadyl alkylphosphonates VORPO3 · H2O

Abstract A series of layered compounds of general composition VO(C n H 2 n +1 PO 3 ) · y H 2 O ( y = 1.5, 1 ⩽ n ⩽ 3; y = 1.0, 4 ⩽ n ⩽ 8) has been synthesized by hydrothermal reaction of V 2 O 3 and the corresponding alkylphosphonic acid in water at 200 °C. The compounds with n ⩽ 3 have structures similar to that of VO(HPO 4 ) · 0.5H 2 O. The compositions with4 ⩽ n ⩽ 8 also are layered, with structures apparently related to that of VO(C 6 H 5 PO 3 ) · H 2 O. The phases with n ⩾ 4 have compositions and structures identical to those of the compounds prepared via water treatment of the benzyl alcohol intercalation compounds VO(C n H 2 n +1 PO 3 ) · H 2 O · C 6 H 5 CH 2 OH, which were reported previously.

A mixed valence heteropolyvanadate, K7Na[AsV4VV7VIV5O43H3]·7H2O

Abstract The reaction of NaVO3 with As2O3, Na2C6O6 and KSCN in water at pH 4.4 yields shiny black crystals of K7Na[AsV4VV7VIV5O43H3]·7H2O. The structure consists of an ϵ-Keggin core {AsV12O40} with three [VO] vertices removed and capped by three [VO] and three [AsOH] units. Crystal data: monoclinic C2/c, a = 40.048(9), b = 13.326(1), c = 18.074(3) A, β = 112.28(1)°, V = 9005.9(14) A3, Dcalc = 2.986 g cm−3, Z = 8, R = 0.063 for 5999 reflections.

Synthesis of Stable Cationic Radicals of Hindered Hexaamino and Triaminobenzene Derivatives and the Study of their Solid State Magnetic Properties

Abstract Both hexakis(dimethylamino)benzene (HDMAB) and 1,3,5-tris(diisopropylamino)benzene (TDIAB) were synthesized by improved procedures. In contrast to the irreversibility of electron oxidations of many triaminobenzene derivatives, we demonstrate that, by substituting three hindered diisopropylamino groups on benzene, stable monocationic radicals can be obtained. In the case of HDMAB its cationic radical can be stabilized in a strong acid medium. The observed bulk spin densities of 0.18–0.23 spins ½ per donor molecule in TDIAB-PF6 and HDMAB-PF6 solids are significant comparing to the diamagnetic properties normally obtained in solids of simple cationic salts of planar organic donor molecules. The results imply that a small degree of molecular spin separation due to the steric effect can readily increase sharply the paramagnetic spin density of solids.

New chemistry to the synthesis of quinoline oligomers and a CVD technique for high temperature conducting thin films

Abstract We report a new concept of catalytic dehydrogenative polycondensation (CDHP) reaction for the synthesis of linear rigid rod-like polyaromatic heterocyclic oligomers. Specifically, we demonstrate this type of condensation leading to a new synthesis of nonsubstituted quinoline oligomers from 1,2,3,4-tetrahydroquinoline in an one-step reaction using transition metal sulfides as catalysts. The method offers a good insight to the synthesis of polyquinoline and some of its derivatives since monomers are readily available and the synthesis can be simplified. From the reaction mechanism a delicate balance between dehydrogenation and polymerization activity of catalyst is required to optimize the yield and the molecular weight of the product in the CDHP reaction. To prepare highly thermal oxidative stable conducting polymers, we developed a chemical vapor deposition (CVD) technique for processing organic oligomers. The technique enable us to fabricate the reproducible high temperature conducting polymer thin films (200 – 2000A) from the polyquinoline based materials with an excellent adhesion to the substrate surface. These films exhibit a low resistivity without chemical doping and high stability at elevated temperatures. The conductivity of the CVD thin films prepared at 900°C were found to be 695, 700, 750 and 920S/cm at 30K, 150K, 300K and 950K, respectively. Interestingly, those samples treated at temperatures above 800°C, the resistivity was found to be very weakly temperature dependent. For example, the 900°C treated sample gives a resistance ratio of R 30K /R 950K equal to only 1.32, and a resistance maximum at 30K.

Low-temperature ferromagnetic intermolecular interactions between galvinoxyl radicals in submicrocrystalline solids

Low-temperature magnetic properties with a positive θ of 4.4 K can be achieved in a powder of galvinoxyl radicals in pure form indicating short-range ferromagnetic intermolecular interactions between neighbouring spins.

Magnetic properties of the doped charge transfer complexes of HMT-HCTMC with a mix-stacked structure

Abstract A charge transfer complex of triplet donor 2,3,6,7,10,11-hexamethoxytriphenylene (HMT) and a symmetrical acceptor tris(dicyanomethylene)cyclopropane (HCTMC) was synthesized. The crystallographic data of this HMT-HCTMC complex showed a molecular packing with the alternate ..D + A − D + A − .. stacking arrangement along the c axis and the [1 2 0] direction in the ab plane. The magnetic properties of HMT-HCTMC and doped HMT-HCTMC complexes were studied. We observed a significant reduction of the magnitude of intermolecular antiferromagnetic spin interaction in the doped complexes. The effect may be attributed to the molecular spin separation induced by the incorporation of arsenic fluoride ions into the complex solid.