Benzene dithiol

Section 5 is on one particular molecule, p-benzene dithiol. This is one of the most commonly studied molecules in molecular electronic transport junctions [7] (although it is also one of the most problematic). Section 6 discusses a separate measurement, inelastic electron tunneling spectroscopy [8, 9] (IETS). This can be quite accurate because it can be done on single molecules at low temperatures. It occurs because of small perturbations on the coherent transport, but it can be very indicative of such issues as the geometrical arrangement in the molecular transport junction, and pathways for electron transport through the molecular structure. 

There are almost 100 papers that discuss benzene dithiol s conductance. As the point about geometric distributions became well understood, it was realized that statistical analysis was extremely useful. Accordingly, electrochemical break junction techniques, both in their original form of crashed electrodes being separated to form the gap or in the newer electrochemistry form, in which a gap is created and then electrochemically modified, have proliferated. The important thing is that statistical measurements can be made [24, 90], with hundreds or thousands of data points. Not surprisingly, distributions are observed (as the earlier computations had suggested). 

Crosstalk has been discussed fairly extensively, as one of a series of interference phenomena that can lead to a different kind of control of molecular transport than has been discussed in Sect. 7.4. It is also possible to observe intramolecular interference effects. For example, with cross-conjugated molecules [163] or benzene dithiol linked in the 1,3 (or meta) configurations [164-171], both are expected to show substantially reduced transport. 

The chloride ions of 143 are displaced by reaction with the dithiolene chelates, disodium maleonitrile dithiolate (Na2 mnt), benzene dithiolate (bdt)... 

Tetramethylpiperidinomethyltrimehtoxysilane 816 and the corresponding 2,2,6,6-tetramethyl-piperidinomethylsilane 817 are the precursors for another family of spirocyclic silicates 818-824, which are accessible upon reaction with a-hydroxy acids, a-amino acids, o-benzene dithiol, and dithioglycol (Scheme 109).821 822... 

Homoleptic gold(III) derivatives with dithiolate, ligands of the type [Au(S-S)2] are well known and are usually prepared from [AuC14] with the dithiol some examples are with 1,2-benzene dithiolate, maleonitriledithiolate, dmit, and so on, [164, 336]. Similar complexes have been reported for bidentate sulfur ligands such as dithiocarbamates, dithiophosphates, and so on, [41]. Other derivatives as the trinuclear species [Au(C6F5)(S2C6H4)]3 [337] or the complex with one nido and one closo-carborane dithiolate are known [338]. Figure 1.72 collects some of these complexes. 

Efficient synthesis of 6,7-dimethoxybenzopentathiepin 102 and 6-(2-aminoethyl)benzopentathiepin 103 (Figure 29), which are sectional structures of varacin, were proposed from 1,2-dimethoxybenzene and 1,2-benzene-dithiol, respectively <1995H(41)893>. 

Finally, a very simple molecular electronic component is benzene-1,4-dithiol, which is readily used as a linker between gold electrodes in the same way as the cobalt terpyridine complex shown in Figure 11.40. Benzene dithiol has been used to demonstrate the thermoelectric effect in molecular electronic systems as a linker between a gold surface and the gold tip of a modified atomic force microscope. Thermoelectricity (termed the Seebeck effect) is the generation of an electrical potential... 

Most of the tetradentate ligands have been synthesized starting from bidentate sulfur ligand precursors. Here, the principal problem was to find a practicable method to alkylate selectively one of two identical sulfur functions. For example, it is impossible to connect intermolecularly two 1,2-benzene-dithiolate units by alkylation in order to obtain a tetradentate ligand. The intramolecular alkylation always prevails according to Eq. 2. 

Nucleophilic aromatic substitution of the fluorine substituents by benzene-dithiolate sulfur atoms (step a), reduction of the nitro compound (step b), diazotization, reaction with KSaCOEt, alkaline hydrolysis, and acidification gave tpS4 H2 (step c). It could be purified via the [Ni(tpS4)]2 complex (Fig. 1), which is readily hydrolyzed with dilute hydrochloric acid to give pure tpS4 H2. 

Final purification by use of metal complexes was also applied in the syntheses of the ligands XS4—H4. These ligands exclusively contain thiolate donors and were prepared by Hahn et al. (23) using 2,3-dimercaptobenzoic acid as starting material (Scheme 8). Isopropyl or benzyl protection of the thiol functions, conversion into the acyl chlorides, reaction with a,oo-diamines, and deprotection of the sulfur atoms enabled the connection of two 1,2-benzene-dithiol units via carboxylic acid amide bonds. 

The series of nickel(II) complexes (Scheme 17) demonstrates the variety of structures found when the S denticity, the bridge length between the benzene-dithiolate units or the donor atoms D in DS ligands (D = additional donor atom) are varied. 

Thio-Mo species are implicated in the turnover of industrial catalysts and enzymes, but mononuclear thiomolybdenyl complexes are very rare. [MoSTp Cb], one of the first complexes of this type, was obtained by reaction of [MoOTp Cl2] with B2S3, and related species [MoSTp X2] (X = aryloxide, alkane thiolate, X2 = catecholate, benzene dithiolate) have been described. 

Due to transdithiolation reactions it was possible to obtain dibenzo-TTF (431) from ammonium benzene dithiolate and 2-chloromethylene-1,3-dithiol in ca. 30% yield <78JOC416>. 

Toluene-3,4-dithh>l. l,2-Dimercapto-4-methyl-benzene dithiol . C7H8S, mol wt 156-27. C 53.80%. H 5.16%. S 41-04%. Prepd from toluene-3.4-disulfonyl chloride with tin and hydrochloric add Mills, Clark, J. Chem. Soc. 1936, 178. 

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