Electronic engineering of a tetrathiafulvalene charge-transfer salt via reduced symmetry induced by combined substituents. Issue 40 (8th October 2019)

• Record Type: Journal Article
• Authors: Kiyota, Yasuhiro; Jeon, Ie-Rang; Jeannin, Olivier; Beau, Maxime; Kawamoto, Tadashi; Alemany, Pere; Canadell, Enric; Mori, Takehiko; Fourmigué, Marc
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 40(2019)
• Page Start: 22639
• Page End: 22646
• Publication Date: 2019-10-08
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c9cp04320a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : A 1 : 1 metallic charge-transfer salt is obtained by cosublimation of ( Z, E )-(SMe)2 Me2 TTF and TCNQ. Abstract : A 1 : 1 metallic charge-transfer salt is obtained by cosublimation of ( Z, E )-(SMe)2 Me2 TTF and TCNQ. X-ray diffraction studies confirm the formation of segregated stacks comprising donor and acceptor molecules in [( E )-(SMe)2 Me2 TTF](TCNQ). The crystal packing features lateral S⋯S interactions between TTF stacks, which is in sharp contrast to that in (TTF)(TCNQ). Structural analysis and theoretical studies afford a partial charge-transfer ( ρ ≈ 0.52), leading to a system with the electronic structure close to quarter-filled. Resistivity measurements reveal that this material behaves as a metal down to 56 K and 22 K at 1 bar and 14.9 kbar, respectively. The thermopower is negative in the metallic regime, indicating the dominant role of the acceptor stacks for the observed conducting behavior. Analysis of single-crystal EPR spectra shows the remaining spin susceptibility at 4.3 K, suggesting the importance of the Hubbard U correction. These results highlight the judicious engineering of electronic and geometrical effects on the TTF core; the combined use of methyl and thiomethyl groups has decreased the TCNQ bandwidth while maintaining the segregated stacks, converting the metal to insulator (M–I) transition to more 4 k F like. In addition, the enhanced S⋯S contacts between the TTF stacks lead to more rapidly decreasing M–I transition temperature under various pressures.