CRYSTAL-STRUCTURE OF A COMPLEX OF PERI-XANTHENOXANTHENE (PXX) WITH TETRACYANOQUINODIMETHANE (TCNQ)

The crystal structure of a 1:1 complex of peri-xanthenoxanthene (PXX) with tetracyanoquinodimethane (TCNQ), C20H10O2.C12H4N4, has been deter mined from single-crystal X-rav diffraction studies. The crystals are triclinic, P1BAR, Z = 1, with the unit cell dimensions a = 6.645(1), b = 8.434(4), c = 11.145(5) angstrom, alpha = 68.00(4), beta = 76.39(5) and gamma = 84.43(5)degrees. The structure (including H-atoms) was re fined from atl data, giving final R(F) = 0.052 for the 1452 reflection s with I > 2sigma(I) and R(w)(F2) = 0.184 for all data. The two molecu les are situated on inversion centres and close to planar, with their least-squares planes almost parallel. The PXX and TCNQ molecules stack alternately along a, with an interplanar distance of ca. 3.3 angstrom . Extraordinary interaction between the stacks is present only as shor t C-H...O and C-H...N contacts. Empirical estimates of the charge tran sfer from bond lengths in TCNQ indicate little or zero charge transfer , suggesting very low conductivity.