D. Nöthe

Electrochemically Generated Peryleniumyl-Hexafluorophosphate and Hexafluoroarsenate: New One-Dimensional Metals

Abstract Compounds of stoichiometry (pe)2(PF6)1.1 × 0.8CH2Cl2(1) (pe = perylene), (pe)2(AsF6)1.1 × 0.7 CH2Cl2 (2), (pe)2(PF6)1.4 × 0.6 THF (3), (pe)2(AsF6)1.5 × 0.5 THF (4) and (pe)3(SbF6)2 × 0.75 CH2Cl2 (5) have been obtained as crystalline samples by electrochemical deposition from CH2Cl2 [(1), (2) and (5)] or from THF [(3) and (4)] solutions of perylene, containing the appropriate counterion. The three compounds (1)-(3) crystallize in isomorphous orthorhombic lattices. (1) forms black needles: space group Pnmn with a = 4.285 A, b = 12.915 A and c = 14.033 A, z = 1. (2) gives black needles, orthorhombic space group Pnmn with a = 4.294 A, b = 13.077 A, and c = 14.132 A, z = 1. The structures of (1) and (2) were solved by direct methods and refined by least squares to final R = 0.148 and R = 0.088 based on 476 and 322 observed reflections. The perylene forms segregated stacks in direction of the a-axis with interplanar distances of 3.40 A and an angle of 37.7° between the bc-plane and the perylene. The ch...

Triplet Spin Excitons in a Sigma-Bonded TCNQ Dimer Salt: N-Ethylphenazinium TCNQ, (NEP+)2 (TCNQ−-TCNQ−)

Abstract The title compound NEP-TCNQ crystallizes with θ-bonded (TCNQ−-TCNQ−)-dimers. We show by model calculations and ESR spectroscopy, that these bonds can be broken by thermal activation. The reverse reaction occurs spontaneously. The excited states are characterized as quasi immobilized triplet spin excitons (TSE) localized on the two “parts” of the former TCNQ-dimer. Additional weaker TSE and doublet signals are observed.

PHENAZINE CATION RADICAL SALTS: CHARGE-TRANSFER COMPLEXES WITH TCNQ*

The first systematic study1 of the conductivities of tetracyanoquinodimethane (TCNQ) salts with closed-shell, diamagnetic M + cations identified the importance of single-crystal work and the generally higher conductivities of complex salts such as M2(TCNQ)3 or M(TCNQ), in comparison to simple 1:l salts like M(TCNQ). Chemical purity and crystal perfection have remained obvious and difficult goals in all subsequent studies of organic conductors or, indeed, of other organic molecular solids. The implication that complex stoichiometry helps in achieving high conductivity has been less widely recognized, a t least until recently. This is due in part to the fact that it is not the stoichiometry itself, but rather the degree of ionity y and the packing arrangement in the structure that are important. When M + is a diamagnetic inorganic ion, the complex salt M2(TCNQ)3 clearly has y =

Crystal and molecular structure and ESR spectra of the 1:1 salt 5‐(1‐butyl)phenazinium (NBP)‐2,2′‐(2,3,5,6‐tetrafluoro‐2,5‐ cyclohexadiene‐1,4‐diylidene)‐bispropanedinitrile (TCNQF4)

on the TCNQ-Y stacks when all sites are crystallographically equivalent and has two ionic T C N Q and one neutral T C N Q site when the sites are very different. On the other hand, the simple salt M(TCNQ) contains only TCNQions and has y = I . The semiconduction observed in simple salts with y = 1 is associated with a correlation energy U for producing doubly occupied TCNQ-2 sites? Either empty TCNQ or doubly occupied TCNQ-’ sites are carriers in an ionic lattice. Charge carriers can be formed without creating TCNQ-* sites for y < I , when there are fewer electrons than sites in the singly filled molecular orbital (MO) of TCNQ-I. The major features of the magnetic, optical, and electric properties of molecular solids based on *-electron donors (D) and acceptors (A) can in fact be understood’ by pursuing the implications of strong electron-electron correlations in these quasi-one-dimensional systems. Indeed, all highly conducting inorganic and organic systems in which there is no direct covalent bonding along the chain appear3 to be based on fractional charges, o r mixed valency in inorganic terminology, with a uniform value of y at each site. The importance of electron-electron correlations in narrow-band organic D and A crystals should not be surprising, since the triplet spin excitons found in

Crystal and molecular structure and EPR triplet spin excitons of NBP TCNQ, the 1:1 salt of 5‐(1‐butyl) phenazinium (NBP) with 2,2′‐ (2,5‐cyclohexadiene‐1,4‐diylidene)‐bispropanedinitrile (TCNQ)

The title compound C28H17F4N6, Mr=513.48, crystallizes in the monoclinic space group P21/c, with a=10.972(2) A, b=17.557(3) A, c=13.523(4) A, β=111.88(2)°, V=2417.36 A3, z=4, and dc=1.411 Mg m−3. Final refinement yielded residuals of R=0.056 and Rw=0.046. The structure consists of (NBP+)2 and (TCNQF−4)2 dimers stacked in a DDAA sequence along the c axis. The NBP+ and TCNQF−4 ions are planar, with interplanar distances of 3.54(2) A for a donor pair and 3.15(3) A for an acceptor pair. The angle between the NBP+ and TCNQF−4 planes is 15.8°. In the ESR experiments, two equivalent species of thermally activated Frenkel triplet spin excitons (TSE), with differently oriented fine structure tensors, are observed. They are located on two TCNQF4 molecular pairs of different orientation. A motion of the TSE in the b direction can be excluded. Additional S=1/2 lines are due to immobile doublet spins on TCNQF−4 radical ions.

TCNQ SALTS OF PLANAR METAL COMPLEX CATIONS: NOVEL MOLECULAR CONDUCTORS AND SEMICONDUCTORS.

The title compound C28H21N6, Mr=441.51 crystallizes in the triclinic space group P1, with lattice constants a=831.5(3), b=965.7(5), c=1638.3(8) pm, α=70.54(3)°, β=71.51(3)°, γ=76.78(3)°, V=1.165(1) nm3, Z=2, dc=1.258 Mg m−3. Final refinement yielded residuals R=0.050 and Rw=0.065. The structure consists of (NBP+)2 π‐bonded dimers and (TCNQ−)2 π‐bonded dimers that alternate along the [101] direction. The structure of NBP TCNQ thus is very similar to that of NBP TCNQF4 (where TCNQF4 is the 2,3,5,6‐tetrafluoro derivative of TCNQ) but the latter salt belongs to the space group P21/c. The NBP+ and TCNQ− ions are planar, with interplanar distances of 344(2) pm for the donor pair, and 316(3) pm for the acceptor pair. The angle between the NBP+ and the TCNQ− planes is 5.9°. In the ESR experiments a single thermally activated ‘‘quasi‐immobile’’ Frenkel triplet spin exciton (TSE) is seen, along with the usual g=2 impurity line and a second set of narrower g=2 lines that are probably due to exchange‐narrowed TCNQ− ...

Structure and Paramagnetism of Strong Charge-Transfer Complexes: 5.10-Dihydro-2.3.5.7.8.10-hexamethylphenazine-tetracyanoethylene (M6P) (TCNE)

Abstract The facile variation of positive charge of oxamide oxime metal complexes, caused by acid-base equilibrium, allows the growth of single crystals of their TCNQ salts. 1:1 salts consist of reqular segregated stacks of the components, with metallic room temperature behaviour of the Ni compound, the Pt compound being a semiconductor. Room temperature conductivities are of the order of 10 Siemens per cm. A 2:3 Pt complex TCNQ salt contains segregated acceptor stacks with half a negative charge per molecule. These stacks run perpendicular to mixed stacks -D-D-A-D-D-A-, with integral charges on donors D and acceptors A.

The average structure of 5.10-Dihydro-5.10-Diethylphenazinium-Iodide (E2P·I1.6): A new linear chain Polyiodide compound

Abstract The potent new donor 5.10-dihydro-2.3.5.7.8.10-hexamethylphenazine was synthesized and reacted with tetracyanoethylene to form a paramagnetic ionic charge transfer salt. The title compound (C18H22N2) (C6N4), (M6P) (TCNE), M r = 394.51, crystallizes in the monoclinic space group P21/n with a = 7.679(3) A, b = 8.458(2) A, c = 15.841(6) A, β = 92.88(3)0, V = 1027.55 A3, d c = 1.288 Mg m−3, and Z = 2. The planar M6P+ and TCNE− radical ions form mixed, regular stacks along b with a distance between M6P+ and TCNE− of 3.4(1) A. Final refinement yielded R-indices of R = 0.092 and R w = 0.058. Epr and static susceptibility data are interpreted in terms of novel disorder involving specific TCNE-allyl exchanges.

Molecular solids containing BEDT-TTF and structurally related transition metal complexes

Abstract Upon oxidation of 5.10-dihydro-5.10-diethylphenazine (E2P) with iodine golden-green lustrous crystals of a compound with stoichiometry E2P.I1.6 were isolated. The compound crystallizes in the tetragonal space group D42 with a = 12.321(2) A and c = 5.330(2) A . The E2P and I form interpenetrating incommensurate sublattices along c, with an iodine repeat distance of 9.7 A. Static susceptibility measurements at room temperature give χg = + 0.994 × 10−6 g−1 × cm3. This corresponds to one unpaired electron spin per two formular units. Single-crystal EPR indicates that the paramagnetism is associated with weakly interacting E2P+ cation radicals. The 300K-d.c. conductivity of 3×10−2Ω−1cm−1 and activation energy of 0.17±0.02eV for single crystals is consequently associated with the polyiodide chains, and not with the E2P+ cation radicals.

Kristallisierte Charge Transfer Addukte von TCNQ und TMPD+ mit Planaren übergangsmetallkomplexen

The special physical properties of BEDT-TTF salts, e.g. their two-dimensional behaviour, are caused by the typical geometry of this donor and the arrangement of the cations in the crystal lattice of its salts. In order to extend the range of physical properties produced by BEDT-TTF like compounds, we synthesized sulfur containing transition metal complexes with a molecular structure very similar to BEDT-TTF. The bis(5.6-dihydro-1.4-dithin-2.3-dithiolate)metallates of the nickel triad can be prepared in different oxidation states as anions and in neutral form. The anionic complexes can be reacted with BEDT-TTF cations.