Eur. Phys. J. B 28, 289-297 (2002)
https://doi.org/10.1140/epjb/e2002-00232-8

Molecular reorientation in pyrene hexafluoroarsenate salts

Physikalisches Institut, Universität Karlsruhe, Wolfgang-Gaede-Str. 1, 76128 Karlsruhe, Germany

Corresponding author: ^a edo@piobelix.physik.uni-karlsruhe.de

Received: 22 March 2002
Published online: 31 July 2002

Abstract

The quasi-one dimensional pyrene (PY) organic conductor (PY)₇(PY)₄(AsF₆)₄ 4CH₂Cl₂  shows parallel as well as 60 rotated PY radical cations in its stacks, but crystallizes in two different modifications I and II. One of the seven intra-stack pyrene molecules is susceptible to a reorientation by 60, that is stable already at room temperature for modification II, but occurs at a hysteretic first order transition between 170 K and 240 K for modification I. Crystal structure, microwave conductivity and static magnetic susceptibility are typical for a quasi-one dimensional organic conductor with Peierls transition at T_P = 73 K (mod. I) or T_P = 105 K (mod. II). The pyrene radical packing is analysed by continuous wave and pulsed electron spin resonance measurements, using 9.45 GHz as well as 425 MHz as measuring frequency. Anisotropy of the conduction electron diffusion constant exceeds 1000 in the metallic phase.