K. Bechgaard

Time-Resolved X-ray Scattering of an Electronically Excited State in Solution. Structure of the 3A2u State of Tetrakis-μ-pyrophosphitodiplatinate(II)

The structure of the (3)A(2u) excited state of tetrakis-mu-pyrophosphitodiplatinate(II) in aqueous solution is investigated by time-resolved X-ray scattering on a time scale from 100 ps to 1 micros after optical pumping. The primary structural parameter, the Pt-Pt distance, is found to be 2.74 A, which is 0.24 A shorter than the ground-state value. The contraction is in excellent agreement with earlier estimates based on spectroscopic data in solution and diffraction data in the crystalline state. As a second structural parameter, the distance between the P planes in the (3)A(2u) excited state was determined to be 2.93 A, i.e., the same as that in the ground state. This result implies that a slight lengthening of the Pt-P bond occurs following excitation.

X-Ray Diffuse Scattering Study of Some (TMTSF)2X and (TMTTF)2X Salts

Abstract X-ray diffuse scattering experiments on the superconducting salts (TMTSF)2X with X = PF6, AsF6 and ClO4 reveal no charge density wave instability, in contrast with the poorly conducting (TMTTF)2PF6 salt. New structural phase transitions coinciding with conductivity anomalies are found in (TMTSF)2NO3, (TMTSF)2ReO4, and (TMTTF)2ClO4. It is suggested that they correspond to order-disorder transitions involving the non-centrosymmetric counter ions. Relationships between these structural instabilities and superconductivity are also discussed.

Diffuse X-ray scattering in the metallic state of TSeF-TCNQ and HMTSeF-TCNQ

Abstract Some results of a X-ray diffuse scattering investigation on the charge transfer compounds TSeFTCNQ and HMTSeF-TCNQ are reported. In the metallic region the results show the formation of a 1-D distortion or a Kohn anomaly in the phonon spectrum. For TSeFTCNQ this is observed below T ∼ 238 K and corresponds to a periodicity of (3.15 ± 0.05) | b | along the chain axis. For HMTSeFTCNQ the distortion was detected even at room temperature and has a period of (2.7 ± 0.1) | b |. In both materials the distortion has both transverse components in contrast to TTFTCNQ. In the insulating state of TSeF-TCNQ below 29 K the 1-D distortions on each stack are correlated to form a 3-D superlattice.

Semi-metallic behaviour of HMTSF-TCNQ at low temperatures under pressure☆

Abstract Some results of electrical resistivity (ϱ) and transverse magnetoresistance measurements on single crystals of the charge transfer compound HMTSF-TCNQ under pressure are reported. There is evidence that dϱ/d T remains positive over the whole temperature range under pressure, and that a T 2 law is obeyed from 0.19 to 2 K at 14 kbar. Together with a relatively large magnetoresistance this is an indication of semi-metallic behaviour.

Electron spin resonance spectroscopy of the organic conductor: (TMTSF)2PF6

Abstract The ESR g-factor, linewidth and spin susceptibility of (TMTSF) 2 PF 6 are each found to have a distinct temperature dependence. The anisotropy of g and of the linewidth for static magnetic fields in the plane perpendicular to the highly conducting axis suggest that spin-phonon scattering is the dominant relaxation mechanism. The metal-insulator transition at 19 K is reflected particularly clearly in the magnetic properties.

Study of the new electron transfer mediators in glucose oxidase catalysis

The steady-state oxidation of glucose oxidase from Aspergillus niger by phenothiazines, phenoxazines, Wursters salts, dithia- and tetrathiaaromatic compounds, and nickelocene was investigated spectrophotometrically and electrochemically. At pH 7.0 the determined oxidation rate constants (TN/Km) vary in the range 103 to 108 M−1·s−1. For phenothiazines, phenoxazine and Wursters salts oxidation constants depend on the redox potential of the electron acceptors, and results were interpreted in the framework of the outer sphere electron transfer theory (Marcus and Sutin, Biochim. Biophys. Acta, 811 (1985) 265). The interpretation of the kinetic results concerning thiaaromatic compounds and metallocenes are complicated due to complex formation with the enzyme active center and aggregation of their oxidized form in buffer solution.

Correlation between linear resistivity and T c in the Bechgaard salts and the pnictide superconductor Ba(Fe 1-x Co x ) 2 As 2 .

The quasi-one-dimensional organic Bechgaard salt

Solution-Based Fabrication of Single-Crystalline Arrays of Organic Nanowires

{(\text{TMTSF})}_{2}{\text{PF}}_{6}

NMR in commensurate and incommensurate spin density waves

displays spin-density-wave (SDW) order and superconductivity in close proximity in the temperature-pressure phase diagram. We have measured its normal-state electrical resistivity

Anomalous magnetoresistance in an organic conductor: (TMTSF)2PF6

{\ensuremath{\rho}}_{a}(T)