Comparison of the Crystal and Electronic Structures of Three 2:1 Salts of the Organic Donor Molecule BEDT-TTF with Pentafluorothiomethylsulfonate Anions SF5CH2SO3-, SF5CHFSO3-, and SF5CF2SO3-

Abstract

Salts of the donor molecule, bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET), with pentafluorothiomethylsulfonate (SF{sub 5}CX{sub 2}SO{sub 3}{sup -}, X = H or F) anions have been prepared. Three phases, {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}SO{sub 3}, {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3}, and {beta}'-(ET){sub 2}SF{sub 5}CHFSO{sub 3} were obtained by electrocrystallization with the corresponding LiSF{sub 5}CX{sub 2}SO{sub 3} electrolytes. The structures of these salts were determined by single-crystal X-ray diffraction, and their physical properties were examined by electrical resistivity measurements as well as by ESR and Raman spectroscopy. The {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}SO{sub 3}, {beta}'-(ET){sub 2}SF{sub 5}CHFSO{sub 3} and {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3} salts are considerably different in their crystal structures, physical properties, and electronic structures despite the similarity in the structures of the SF{sub 5}CX{sub 2}SO{sub 3}{sup -} (X = H, F) anions. The {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}SO{sub 3} salt has two kinds of ET donor molecules with considerably different charge densities. The electronic structure of {beta}'-(ET){sub 2}SF{sub 5}CHFSO{sub 3} has both one-dimensional (1D) and two-dimensional (2D) Fermi surfaces which are similar to those found in the organic superconductor {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}. The ESR data for the {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3} salt indicate that it opens a spin gapmore » below 45 K. The differences in the physical properties of the three salts were analyzed by calculating the HOMO-HOMO interaction energies between nearest-neighbor ET molecules in their donor molecule layers.« less