Paul J. Nigrey

Stoichiometry of bulk superconducting La2CuO4+δ: A superconducting superoxide?

Abstract A variety of analytical tools have been combined to show that bulk superconducting La2CuO4+δ has a La to Cu ratio of 2.00 (±0.02) and an oxygen stoichiometry of 4.13 (±0.1). The combination of these analytical results and magnetization data with a model leads us to suggest that the excess charged oxygen is introduced as O-2.

Organic metals: Synthesis, structure and properties of (BMDT-TTF)2Au(CN)2

Abstract A novel 2:1 salt, di[bis(methylenedithio)-tetrathiafulvalene] dicyanoaurate(I), (BMDT-TTF)2Au(CN)2, has been prepared by electrochemical oxidation in 0.016 M (C4H9)4N Au(CN)2/chlorobenzene. Single crystal X-ray diffraction studies indicate that the salt is monoclinic, P21/a, with a = 10.824(7), b = 8.420(5) c = 15.614(8) A and β = 102.46(4)° having a unit cell volume of 1390 A3 and two molecules per unit cell exhibiting an unusual packing motif. The four-probe d.c. electrical conductivity was found to be metallic at room temperature, having a value of nearly 300 (ohm cm)−1. Electron spin resonance studies show that above 70 K the spin susceptibility is relatively large (7 × 10−4 emu/mole) and independent of temperature, consistent with the Pauli susceptibility for a metal.

Synthesis of organometallic mixed sulfur-selenium π-acceptor molecules

The reactive dianion, 4,5-diselenolato-1,3-dithiole-2-thione (dsit) was prepared by the reaction of 1,3-dithiole-2-thione with in-situ generated lithium diisopropylamide and finely powdered elemental selenium. Addition of methanolic-ammoniacal solutions of the appropriate metal (nickel and palladium) dichlorides to the above reaction mixture followed by methanolic solutions of tetraalkylammonium [tetrabutylammonium (TBA) and tetraethylammonium (TEA)] bromide, results in the precipitation of dark colored solids from the solutions. Isolation and purification of these solids revealed that the solids had the general composition (TAA)2[M(dsit)2] where TAA were tetrabutylammonium or tetraethylammonium anions and M were Ni(II) and Pd(II). Electrochemical or chemical oxidation of the nickel(II) organometallic complexes resulted in the formation of the π-acceptor (TBA) [Ni(dsit2)] while a similar reaction with the palladium(II) complexes failed to produce the equivalent (TAA) [Pd(dsit)2].

Bis(2-Thione-1,3-dithiole-4,5-diselenolato)nickelate(II): A Precursor for Mixed Sulfur/Selenium Heterocycles

Abstract The synthesis of bis(tetrabutylammonium)-bis(2-thione-1,3-dithiole-4,5-diselenolato)nickelate(II) (1) is reported. A general reaction scheme for the preparation of 4,5-alkylseleno-1,3-dithiole-2-thione is described and exemplified with the synthesis of 4,5-methylenediseleno-1,3-dithiole-2-thione.

Synthesis and properties of BEDSe-TTF☆

Abstract We report the synthesis and properties of the π-electron donor molecule 4,5:4′,5′-bis(ethylene-1,2-diseleno)-tetrathiafulvalene (BEDSe-TTF) as well as the properties of a novel charge-transfer (C-T) salt derived from it. BEDSe-TTF was obtained in a 25% overall yield by a three step reaction starting from the organometallic complex, bis(tetrabutylammonium)-bis(2-thione-1,3-dithiole-4,5-diselenolato)nickelate(II). A single crystal X-ray structure determination of BEDSe-TTF showed it to be monoclinic, P21/n, with a = 6.842(2), b = 14.047(5), c = 16.094(5) A and β = 94.49(3)° having a unit cell volume of 1542A3 and four molecules per unit cell. Electrochemical oxidation of BEDSe-TTF gave single crystals of BEDSe-TTF+I3−. The structure of this 1:1 C-T salt was also monoclinic, P21/n, with a = 12.503, b = 10.592, c = 15.842 A and β = 100.12° having a unit cell volume of 2065.4 A3 and four molecules per unit cell.

The Synthesis, Crystal Structure, Electrical Conductivity and Band Electronic Structure of (BPDT-TTF)2lCl2

Abstract (BPDT-TTF)2ICl2 is a synthetic metal salt composed of the electron donor molecule bis(propylenedithio)tetrathiafulvalene (BPDT-TTF, C12H12Sk) and the linear iododichloride anion, ICl2 −. The crystal structure of (BPDT-TTF)2ICl2, determined at 298 K and 120 K, closely resembles those of the organic metals and semiconductors based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, C10H8H8), in that all of these materials contain sheetlike donor molecule networks sandwiched between anion layers. In contrast to the (BEDT-TTF)2X salts, however, there is a total absence of S···S contact distances less than ∼3.6 A (the van der Waals radius sum) within the donor-molecule network of (BPDT-TTF)2ICl2. In addition, each stack of BPDT-TTF molecules is also strongly dimerized. The lack of short S···S contact distances at both 298 K and 120 K appears to be a consequence of the bulky propylene groups of BPDTTTF compared to the smaller ethylene groups of the BEDT-TTF molecule. Based upon four-probe a.c. resistiv...

Synthesis, structure and properties of (BMDT-TTF)2Au(CN)2☆

Abstract A novel 2:1 salt, di[bis(methylenedithio)-tetrathiafulvalene] dicyanoaurate(I) (BMDT-TTF) 2 Au(CN) 2 , has been prepared by electrochemical oxidation. The structure was monoclinic, P2 1 /a, with a = 10.824(7), b = 8.420(5), c = 15.614(8) A and β = 102.46(4)°, V = 1390 A 3 , and Z = 2, having an unusual packing motif. The electrical conductivity is metallic down to 76 K at which point an apparent structural phase transition to a semimetallic state occurs. The spin susceptibility is relatively large and independent of temperature above 70 K as expected for a metal. Below 70 K the susceptibility is Curie-like suggesting 0.1 localized spins per unit cell.

Synthesis, structure, and properties of (BPDT-TTF)2IBr2☆

Abstract We report the preparation of di[bis(propylenedithio)-tetrathiafulvalene] iododibromide, (BPDT-TTF)2IBr2, by electrochemical oxidation in benzonitrile. The crystals belong to the triclinic ( P 1 , Z =1) system with the following lattice constants: a =9.259 (2), b = 16.102 (3), c =6.802 (2) A , α=92.46 (2), β=111.73 (2), andγ=91.15 (2)°. The crystal structure of this material was found to be isomorphic with (BPDT-TTF)2I3 and the di[bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF or ET) trihalides. Ambient pressure electron spin resonance (ESR) and low-frequency ESR measurements are discussed.

Synthesis, Structure and Properties of BEDT-TTF Derivatives

Because of the unique transport properties of charge-transfer (C-T) complexes based on the π-electron donor molecules, 4,5,4′,5′-Bis(alkyldithio)-tetrathiafulvalene1, the properties of partially selenium substituted donors bis(alkyldiseleno)-tetrathiafulvalene (BADSe-TTF) were investigated. These molecules are of particular interest to us since much of the current research in this area2 has focused on increasing the dimesionality of the transport 3,4 in C-T salts derived from these donors.