Benzene dithiol conductance

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). 

Varga and Pantelides presented a new method, based on the ab initio, density-functional theory, with which the I — V characteristics of such a system can be calculated. Subsequently, they used their approach to study two systems, i.e., a benzene-dithiolate molecule between two gold electrodes and a finite carbon nanotube between two aluminum electrodes. As typical examples we show in Fig. 51 the current, I, and the conductance, IjV, as a function of applied voltage, V, for the first example. That / is highly non-linear as a function of V is readily identified. The non-trivial current distribution in the molecule under an applied external potential is also seen in the figure. 

Fig. 51 (Top part) Calculated I — V characteristics as well as the conductance for a benzene-dithiolate molecule between two gold electrodes. (Bottom part) The x component of the current in the same system for a fixed value of V. The colour coding is given to the right. Reproduced with permission of American Physical Society from ref. 157.

The conductance of a molecular junction was measured in 1997.26 As shown in Figure 5.2, two Au wires were covered with SAMs of benzene-1,4-dithiol in THF. The wires were bent until they broke, and the broken ends were brought together in picometer increments... 

FIGURE 5.2. The measurement of conductance through a single molecule of benzene-1,4-dithiol using a break junction experiment. 

The first molecular measurement using MCBs was reported in 1997 by Reed and coworkers [37], who measured the conductance of a single benzene-1,4-dithiol molecule (83a). This work was followed in 1999 by measurements on oligothiophene 105 by Bourgoin and coworkers [38]. 

The conducting AFM method has revealed interesting details of the single molecule conductance of carotene molecules. The electronic properties of carotenoids are of interest since they play a role in their biological function, especially their optical properties which are a manifestation of their delocalised electron structure. The structure of the dithiolated carotenoid used in a study by Ramachandran et al. is shown in Fig. 7-21. A synthetic molecular wire 2,5-di(phenylethynyl-4 -thioacetyl)benzene, also appraised by conducting AFM is also shown in Fig. 7-21. The measured low bias resistance of the carotenoid molecule was found to be (4.9 0.2) GQ. After... 

Figure 7-21. Molecular structures the dithiolated carotenoid and a synthetic molecular wire 2,5-di(phenylethynyl-4 -thioacetyl)benzene whose single molecule conductance has been determined by conducting AFM. ...

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