STRUCTURE OF A CHARGE-TRANSFER COMPLEX, DITHIENO[3,4-B-3',4'-D]THIOPHENE-TETRACYANOQUINODIMETHANE (DTT1-TCNQ)

Dithieno[3,4-b:3',4'-d]thiophene-tetracyanoquinodimethane, C8H4S3.C12H4N4, M(r) = 400.51, monoclinic, P2(1)/c, a = 7.272 (3), b = 7.674 (3), c = 32.613 (9) angstrom, beta = 93.6 (2)-degrees, V = 1816 (1) angstrom-3, Z = 4, D(x) = 1.464 g cm-3, Cu K-alpha radiation, lambda = 1.54184 angstrom, mu = 18.16 cm-1, F(000) = 816, T = 293 K, R = 0.085 based on 1843 reflections (F(o) > 4-sigma). The low accuracy of this structural determination is due to the fact that only needle-shaped single crystals shorter than 70-mu-m were obtainable by either solvent or melt crystallization. The structure consists of the facing of discrete dimers (DTT1-TCNQ). No short contacts are observed in the crystal packing. The geometric features are very close to those found in an isomorphous charge-transfer complex (DTT-TCNQ). The low degree of charge transfer is also confirmed in this alternated stack structure.