The UV−vis spectroscopy and cyclic voltammetry of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) were studied in the absence and presence of pyridine (Py) or triethylamine (TEA) in acetonitrile solutions in order to examine the influence of acid−base processes on the redox behavior of DMcT. In solutions containing Py, DMcT can be singly deprotonated to give the anionic species, DMcT-. In solutions containing TEA, DMcT can be either singly or doubly deprotonated to give the anionic species, DMcT-, or the dianion, DMcT2-, depending on the stoichiometry. These acid−base processes were monitored using UV−vis spectroscopy, and those results are reported here. The cyclic voltammetry of both systems was also examined in the absence and presence of Py or TEA. These experiments clearly showed that deprotonation of DMcT results in facilitation of its electrochemical oxidation, leading either to a disulfide-containing dimer or a disulfide-containing polymer, depending on conditions. The relevance of these results to the use of DMcT as a cathode material in lithium secondary batteries is discussed.

No abstract

No abstract

The effects of pyridine and several derivatives (3-chloropyridine and lutidine) on the redox reactions of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) and the disulfide dimer of DMcT have been examined using cyclic voltammetry and UV−vis spectroscopy. In the presence of these bases, the oxidative coupling reactions of DMcT and its disulfide dimer to give a disulfide-containing polymer are facilitated, presumably due to proton-transfer processes with the bases. The potentials at which the oxidative polymerization and reductive depolymerization occur in the presence and absence of such proton transfer reagents are discussed. Also, it is observed that the oxidation of DMcT is facilitated in the presence of DMSO or NMP. The relevance of these results to the possible use of DMcT/polyaniline composite materials as a cathode material in secondary lithium batteries is discussed, especially with regard to the potentials at which the various redox processes can occur.

The synthesis and characterization of poly(thiophenylenesulfonic acid), a novel class of polyaromatic electrolyte possessing up to 2.0 sulfonic acid groups per phenylene unit (m = 2.0), are described. 4-(Methylsulfinyl)diphenyl sulfide (1) was polymerized in sulfuric acid upon heating (<140 °C) or in the presence of SO3 to yield a sulfonated poly(sulfonium cation) (4), which can be converted to the corresponding sulfonated poly(thiophenylene). The precursor method using the soluble poly(sulfonium cation) makes it easy to control the sulfonation reaction in a homogeneous system. The resulting poly(thiophenylenesulfonic acid), unlike the nonsubstituted polymer, is soluble in water and methanol and can form a transparent film. The sulfonated polymer exhibits a good water affinity and an excellent proton conductivity due to the high carrier concentration. The highest conductivity (σ = 4.5 × 10-2 S cm-1) was achieved for the polymer with m = 2.0 at 80 °C.

No abstract

A method is described by which the disulfide dimer of 2,5-dimercapto-1,3,4-thiadiazole (diDMcT, see Scheme 1) can be oxidatively intercalated into the layered structure of a V2O5 xerogel. This intercalation reaction produces a new organic−inorganic composite material with a layer spacing of 13.5 Å, in contrast to the 11.55 Å spacing for the parent V2O5 xerogel. During this oxidative intercalation, the diDMcT is polymerized to produce a polymer with thiadiazole rings linked by disulfides in the polymer main chain (PDTT, see Scheme 1). The composite material is characterized by UV−visible spectroelectrochemistry, X-ray diffraction, FTIR, and electrochemistry. The electrochemical experiments comprised charging (oxidation) and discharging (reduction) of the material, with the bulk of the redox reaction occurring over a broad potential range of 0.5 to −0.6 V versus saturated calomel electrode. The cyclic voltammogram of the composite material shows features that can be attributed to the DMcT−PDTT redox response. However, during or after reduction of the composite, the monomeric DMcT dithiolate appears to be expelled from the V2O5 interlayer region, leading to an evolution of the electrochemical response back to that of the original V2O5 material. Evidence is presented suggesting that the V2O5 host material facilitates the redox reactions of the thiol−disulfide redox couple while it is within the interlayer region.

No abstract