X-Ray crystal structure and properties of (1,4-pyrazinio)bis(dicyanomethylide)(diazaTCNQ)

Abstract

The title compound has been synthesized by the reaction of pyrazine with tetracyanoethylene oxide in refluxing toluene. Single-crystal X-ray structure analysis has been performed on tetragonal crystals of space group P4₂/mnm with Z= 2. The cell constants are a= 8.781(2), c= 5.916 8(7)Å, and V=456.2(2)ų. Block-diagonal least-squares refinement, based on 341 independent reflections with |F₀|>3σ(F), yields R 0.047. The centres of the strictly planar diazaTCNQ (DATCNQ) molecules are located on (0,0,1/2) and on (l/2,1 /2,0), the molecular planes being parallel to the c plane and perpendicular to one another. DATCNQ exhibits a band at 635 nm due to an intermolecular interaction in the powder reflectance spectrum and behaves as a semiconductor with an electrical resistivity of 2.6 × 10¹⁰Ω cm as a compacted pellet at 25 °C. DATCNQ reacts with bromine in hexane to give DATCNQ·Br_x(X=0.05 and 0.1 1), which exhibits resistivities of 2.2 × 10⁸ and 3.2 × 10⁶Ω cm at 25 °C.