G. Rindorf

Unusual structure-related magnetism in the organic conductor TSF(Ni(dmit)2)3 (tetraselenafulvalenium-tri-(bis-(4,5-dimercapto-1,3-dithiole-2-thione)nickel)-ate)

Abstract TSF(Ni(dmit) 2 ) 3 crystallizes in the triclinic space group PI with unit cell dimensions a = 5.875(1), b = 11.846(1), c = 18.873(1) A , α = 71.35(1) , β = 81.63(1), γ = 78.16(1)°. Thermopower and electrical conductivity measurements show semiconducting behaviour localized in the Ni(dmit) 2 network. At 65 K the unit cell doubles in the a direction and this feature is utilized in explaining an unusual cross-over from a Bonner-Fischer model to a simple singlet-triplet magnetic behaviour in the sheets of weakly interacting TSF cation radicals.

The Crystal Structure of 1,6-Dithiapyrene(DTP)-7,7,8,8-Tetracyano-P-Quinodimethane(TCNQ)

Abstract The crystal structure of the charge-transfer complex between 1,6-dithiapyrene(DTP) and 7, 7,8,8-tetracyano-p-quino-dimethane(TCNQ) is reported. The structure correlates well with the observed physical properties.

The structure of 12-(tetrathiafulvenyl)-11-dodecenoic acid at 120 K

Abstract The structure of C 18 H 24 O 2 S 4 (TTFC 11 H 20 COOH) has been determined at 120 K. TTFC 11 H 20 COOH, M r = 400.65, crystallizes in the monoclinic space group P2 1 /c with a = 18.117(5), b = 9.152(4), c = 12.100(3) A, s = 102.68(2)°, V = 1957(1) A 3 , Z = 4 and D c = 1.361 g cm −3 . Least-squares refinement gave R = 0.0898 for 788 observed unique reflections. The TTF parts of the molecules are not stacked, but are coupled into pairs with the usual overlap, double bond over ring. The high R -value reflects the disorder around the double bond in the aliphatic chain.

Crystal structures containing the donor BIS(dimethyltetrathiafulvalene)ethane

Abstract Bis(dimethyltetrathiafulvalene)ethane (BDMTTFE) is a new donor molecule with two TTF moities [1a]. The crystal structures of two compounds containing this molecule have been determined. (BDMTTFE)AsF 6 , 1 2 C 4 H 7 N has a triclinic structure in which the BDMTTFE units are planar and uniformly stacked in a zig-zag manner along the α axis (7.133 A). AsF 6 − and disordered solvent molecules of butyronitrile are situated between the stacks BDMTTFE-DMTCNQ is a charge-transfer salt with dimethyl-TCNQ. The structure contains segregated regular stacks along the α axis (3.867 A) of planar donor molecules and acceptor molecules.

Synthesis and Properties of Trimethyl-TSF Containing Alloys of the TMTSF2, Family

Abstract Cation-radical salts of the general formula (TriMTSFzTMTSF1-z) 2 (X = PF6, Clo4, z ranging from 0 to 0.3) were isostructural. The incorporation of TriMTSF resulted only in minor changes in the transport properties, but the superconducting ground state was completely suppressed.

The structure of N-(n-Propyl)-quinolinium-(TCNQ)2 at 100 K

Abstract The structure of (C 12 H 14 N) (C 12 H 4 N 4 ) 2 , (NPrQn(TCNQ) 2 ), has been determined at 120 K. NPrQn(TCNQ) 2 , M r = 580.63, crystallizes in the triclinic space group P1 with a = 7.514(3), b = 14.069(1), c = 15.208(2) A , α = 65.65(1)°, s = 80.32(2)°, γ = 86.82(2)°, V = 1443.6(6) A 3 , Z = 2 and D c = 1.336 g cm −3 . Least squares refinement gave R = 0.0407 for 3198 observed unique reflections. TCNQ molecules are stacked along the b axis in tetramers containing two inequivalent molecules. The NPrQn molecules are situated between the TCNQ stacks. The geometry of TCNQ molecules does not change significantly in comparison with room-temperature values. There is an increased tetramerization in the low-temperature phase, thermal contraction taking place within tetramers only and not affecting inter-tetramer distances. The latter may be explained assuming a lattice distortion originating in exciton-exciton interactions, competing with thermal effects.

Organic conductors. 2,3,6,7-Tetramethyl-1,4,5,8-tetraselenafulvalenium 2,5-dimethyl-7,7′,8,8′-tetracyano-p-quinodimethanide

2,3,6,7-Tetramethyl-1,4,5,8-tetraselenafulvalene reacts with 2,5-dimethyl-7,7′,8,8′-tetracyano-p-quinodi-methane to give a highly conducting organic solid.

RADICAL CATION SALT BASED ON ORGANIC DONOR WITH CLOSE-LYING HIGHEST OCCUPIED MOLECULAR ORBITALS

Abstract Triclinic crystals with segregated stacks of donor and acceptor molecules are produced by electrocrystallization of 4,4′,6‴,4⁗- Tetra-Methoxy-Hexa -m- Phenylene in the presence of μ-oxalato-bis[tetrachlorostanate(IV)] dianions. Molecular orbital calculations show that the energy splitting between the two highest occupied molecular orbitals of the organic donor is 50 meV or less. Measured physical properties of this charge transfer crystal are presented and discussed in light of the possible ferromagnetic interactions between unpaired electrons in a stack of organic molecules with close lying highest occupied molecular orbitals.

Crystal Structure Studies of Organic Superconductors

X-ray crystal structure determinations have been carried out on (TMTSF)2X, where TMTSF = tetramethyltetraselenafulvalene and X = PF6-, ClO4-, ReO4-. These solids exhibit superconductivity at low temperature (~ 1 K); for PF6- and ReO4- hydrostatic pressure of the order 10 kbar is also required. This paper deals with a description and a comparison of the crystal structures, which have been determined at ambient temperature and pressure. Possible relationships between structural features and physical properties are discussed.

Superconductivity in (TMTSF)2Clo4 at Zero Pressure

Abstract The organic charge transfer salt di-tetramethyl-tetraselenafulvalenium perchlorate becomes superconducting with transition temperatures from 0.9-1.4 kelvin. We compare our results to those of other groups and discuss possible reasons for the observed differences. Preliminary results are given for an alloy with the corresponding perrhenate.