A New Synthetic Metal Precursor: Dimethyltetrathiotetracene and Related Compounds
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A NEW SYNTHETIC METAL PRECURSOR: DIMETHYLTETRATHIOTETRACENE AND RELATED COMPOUNDS MEGH SINGH, M. THOMAS JONES, NIGAM P. RATH, AND TOSHIO MARUO, DONG MIN Louis, Department of Chemistry, University of Missouri-St. St. Louis, 140 63121 ABSTRACT The successful synthesis of dimethyltetrathiotetracene has been achieved in our laboratory and an account of (DMTTT) the details of the synthesis has been reported. Reported herein are studies of the physical properties of DMTTT and some of its Both 1:1 and 2:1 DMTTTX charge transfer salts have chemistry. been prepared and are in the process of being characterized in Comparisons of physical properties and the our laboratory. results of studies such as single crystal x-ray diffraction, cyclic voltammetry and electrical solid state ESR spectra, these comparisons reveal conductivity are reported. To date, considerable similarity between the properties of any given corresponding and its salt charge transfer DMTTT tetrathiotetracene (TTT) charge transfer salt. INTRODUCTION The electron donor tetrathiotetracene (TTT) forms charge transfer salts which at room temperature possess some of the highest electrical conductivities of any known synthetic metal (e.g.
TTT 2 I
3
where or= 3 x 103 S/cm)
TTT and its homologs are to purify. In addition,
[2-8].
Unfortunately,
rather insoluble and hence difficult TTT 2 I 3 undergoes a metal-to-insulator
transition at 35K. Thus, the synthesis and characterization of dimethyltetrathiotetracene a new synthetic metal precursor, Among the (DMTTT), and related compounds was initiated. reasons for the synthesis of DMTTT are to obtain a compound with improved solubility and to investigate the question of whether a donor with symmetry C2 v will resist undergoing the metal-to-insulator transition better than the parent which has symmetry D2 h.
compound
The details of the synthesis of DMTTT and characterization are presented elsewhere [1].
chemical
its
CYCLIC VOLTAMMETRY OF DMTTT Cyclic voltaumetric traces for DMTTT and TTT are shown in They demonstrate that in benzonitrile with 0.10 M Figure 1. (n-C 4 H9 ) 4 NPF 6 as the supporting electrolyte and Ag/AgCl as the reference electrode that both materials undergo a two step reversible one electron electrochemical oxidation where the Mat. Res. Soc. Symp. Proc. Vol. 173. •1990 Materials Research Society
150
half wave oxidation potentials for DMTTT are more negative than those observed for TTT.
/,!,
i
+1.0V
-0.5 V
0.0 V
\, / _ _ DMTIT
TIT
Figure 1. Cyclic Voltammograms of DMTTT and TTT ELECTRONIC SPECTRA OF DMTTT AND DMTTT+ IN SOLUTION electronic absorption spectra DMTTT and +DMTTT+ The dissolved in benzene are shown in Figure 2. The DMTTT were prepared by the addition of trifluoroacetic acid to solutions of DMTTT.
DMTTT
5.4
.2
400
660 wavelength (nrm)
Figure 2.
Electronic Absorption Spectra of DMTTT and DMTTT+
800
151
SOLUBILITY OF DMTTT AND TTT more Preliminary measurements indicate that DMTTT is soluble in monochlorobenzene than TTT which is one of the goals which we had hoped to
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