Synthesis, characterization, and dc conductivity of hydrogen-bonding dibenzotetrathiafulvalene (DBTTF) based salts

The synthesis, characterization, and dc conductivity of organic conductors, 1 -[2-(1,3-benzodithiol-2-ylidene)-1,3-benzodithiol-5-yl]ethylammonium tetrafluoroborate ([DBTTFCH(Me)NH(3)(+)]BF(4)(-)) and 1-[2-(1,3-benzodithiol-2-ylidene)-1.3-benzodithiol-5-yl]ethylammonium bromide ([DBTTFCH(Me)NH(3)(+)]Br(-)) salts are presented. These salts are prepared by mixing the corresponding primary amine and Bronsted acid in a one-to-one ratio without electrochemical oxidation. The change in the electronic state of insulating DBTTFCH(Me)NH(2) into conductive [DBTTFCH(Me)NH(3)(+)]X(-) (X = BF(4) and Br) salts and the carrier generation upon salt formation were confirmed by diffuse reflectance (UV-vis) and ESR spectra. The concentration of localized radicals is estimated to be 1 radical/3.3 units and 1 radical/1.8 units for BF(4) and Br salts, respectively. The possible carrier generation mechanism is proposed by (1)H NMR and ESI-TOE-MS spectroscopic analyses. The dc conductivity and the activation energy are sigma(pi) =2.3 x 10(-3) S/cm with 0.24 eV for the BF(4) salt, and sigma(pi) = 1.3 x 10(-3) S/cm with 0.21 eV for the Br salt. (C) 2009 Elsevier B.V. All rights reserved.