Synthesis, Crystal Structure, and Physical Properties of the Charge-Transfer Complex Bis[benzo[1,2-c:3,4-c′:5,6-c″]trithiophene]–tetrafluorotetracyanoquinodimethan, (BTT)2(TCNQF4)

• Published in: Bulletin of the Chemical Society of Japan Vol. 61; no. 7; pp. 2303 - 2308
• Main Authors: Sugano, Tadashi, Hashida, Takashi, Kobayashi, Akiko, Kobayashi, Hayao, Kinoshita, Minoru
• Format: Journal Article
• Language: English
• Published: The Chemical Society of Japan 01.07.1988
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.61.2303

The semiconductive 2:1 charge-transfer complex between benzo[1,2-c:3,4-c′:5,6-c″]trithiophene and 2,2′-(2,3,5,6-tetrafluoro-2,5-cyclohexadiene-1,4-diylidene)bis[propanedinitrile], (BTT)2(TCNQF4), crystallizes in the monoclinic system, space group P21⁄c, with the following cell constants: a=8.893(2) Å, b=10.589(2) Å, c=18.528(4) Å, β=114.52(1)°, V=1587.5(10) Å3, Dx=1.61 g cm−3, and Z=2. The crystal structure of (BTT)2(TCNQF4) consists of stacking columns of alternating donor dyads and acceptor monads (DAD units) along the crystallographic b axis. Side-by-side sulfur-sulfur contacts shorter than the sum of the van der Waals radii were found along the axis between BTT molecules on the neighboring columns. Polarized reflectance spectra were measured with the single crystal of (BTT)2(TCNQF4) at room temperature, showing a charge-transfer band polarized parallel to the stacking direction. The degree of charge transfer was estimated to be 0.21 from the oscillator strength and the transition energy of the charge-transfer band. From this, as well as the electric and magnetic properties of the complexes and the atomic distances for TCNQF4, it was concluded that (BTT)2(TCNQF4) is a weakly ionized charge-transfer complex.