Crystal and molecular structure of thieno[2″,3″:4′,5′]thieno[2′,3′-d]thieno-[3,2-b]thiophene as a hydrogen-poor heterocycle

Abstract

The crystal and molecular structure of the polythiophene 4 and its charge-transfer complex with tetracyanoquinodimethane (TCNQ) have been determined. Crystal data: 4, C₁₀H₄S₄, M= 252.38, monoclinic, P2₁/n, a= 11.462(1), b= 4.026(1), c= 10.437(1)Å, β= 103.77(1)°, V= 467.8(1)ų, Z= 2, D= 1.792 g cm^–3; 4·(TCNQ), C₂₂H₈N₄S₄, M= 456.60, triclinic, P, a= 7.533(1), b= 10.807(1), c= 7.094(2)Å, α= 90.12(2), β= 92.13(2), γ= 124.55(1)°, V= 475.1(2)ų, Z= 1, D= 1.596 g cm^–3. The molecules in the crystals of 4 are arranged in a zig-zag fashion along the diagonal line through the a and c axes, with notably short intermolecular S–S distances (3.482 and 3.526 Å). The occurrence of short S–S contacts, which are not observed in the lower homologues of the linearly-condensed polythiophenes 2 and 3, are discussed in terms of the low S : H ratio on the molecular periphery. A short S–S contact (3.604 Å) was also observed in the crystal of a 1 : 1 charge–transfer complex of 4 with TCNQ, which forms a mixed stack of donor and acceptor molecules.