TCNQ salts

A = acceptor) is a linear chain of parallel stacked TTE molecules. The TTE molecules are registered directiy above one another, with anions residing in sites between the TTE chains. Unlike the situation found for the TCNQ salts, the TTE molecules in these soHds are equally spaced along the chain. Substantial TT-ovedap exists between the TTE molecules in the chain, providing for conduction along the stacking direction (Eig. 4). 

Charge-Transfer Salts. Most charge-transfer salts can be prepared by direct mixing of donors and acceptors in solution. Semiconducting salts of TCNQ have been prepared with a variety of both organic and inorganic counterions. Simple salts of the type TCNQ can be obtained by direct reaction of a metal such as copper or silver with TCNQ in solution. Solutions of metal iodides can be used in place of the metals, and precipitation of the TCNQ salt occur direcdy (24). 

More highly conducting TCNQ salts of the form M (TCNQ)(TCNQ ) are also easily synthesized, where M can be any one of a variety of organic cations. These salts can be prepared by a number of different methods, though a general method involves mixing of a simple salt with TCNQ in solution. The precipitated salt can then be obtained by filtration. 

Phenazine, 5-methyl-, TCNQ salt electrical conductivity, 1, 348 (65CJC1448) Phenothiazine X-ray, 3, 1010 (68CC1656)... 

Tetraselenafulvalene, tetramethyl-, hexafluorophosphate-, TCNQ salt X-ray, 1, 355 <79AX(B)772>... 

The synthesis of Au(ppy)(CxH4Sg) and Au(ppy)(C 10-C6SX), including the crystal structure of the former, have been reported [97]. The triiodide and TCNQ salts of both complexes have also been prepared by chemical oxidation. Analysis of the EPR spectra indicates that the oxidation is centered on the dithiolate ligands. High room temperature conductivities of 2-4 x 10-2 S cm-1 were measured on compacted polycrystalline samples for the oxidized complexes. 

To avoid having different-sized Schottky barriers at the two interfaces, the same metal (or metals with almost the same work functions) should be used for both electrodes. For example, the different work functions of Pt and Mg made studies of glass I Pt I molecule I Mg I Ag sandwiches hard to interpret [34]. In that case, Mg probably reacted with the end of the molecule containing the strong acceptor TCNQ to form a TCNQ-salt Schottky barrier that dominated the electrical asymmetry [34], With a different molecule lacking TCNQ, the dominating Schottky barrier effect was eliminated [35, 36],... 

Fig. 7 Crystal structure of (CHC )(TCNQ) salt, (a) Uniform segregated stacks of CHC and TCNQ. (b) CHC ribbons by complementary hydrogen bonds and TCNQ form a layer within a bc-plane (hydrogen bonds red dotted lines), (c) Formation of three-dimensional structure (//a) between hemiprotonated cytosine pair and RTCNQ species...

In Table I, the results of this experiment are compared to reflectance spectra measured for other simple and complex metal-TCNQ salts. We found that the CN stretching mode in reflectance measurements shifted to higher frequency by about 100 cm from absorption measurements made on the same material. The peak in the reflectance band at 2320 cm for the Cu-TCNQ film prior to the application of a field is consistent with the values measured for the simple (1 1) salts of Li+(TCNQ ) and Cu+(TCNQ") tabulated in Table I. These crystalline materials are simple salts which do not contain neutral TCNQ . On the other hand the spectra of a Cu-TCNQ film after the application of an applied field closely resembles the spectra of Cs2 (TCNQ [ )3 with two CN stretching modes separated by 20 cm. Cs2(TCNQ )3 is a complex salt which contains neutral TCNQ and radical-anion TCNQ . (11)... 

The diffuse reflectance spectra reported in Table I show that it is possible to assign a CN stretching frequency to both neutral and radical-anion TCNQ in crystalline samples of metal-TCNQ complexes because the reflectance peak for neutral TCNQ is shifted 20 cm higher in frequency than for radical-anion TCNQ". Specifically, the reflectance data for Cu-TCNQ when compared to other metal-TCNQ salts of known composition strongly suggests that neutral TCNQ is not present in the unswitched Cu-TCNQ films. On the other hand, the additional peak that appears in the spectra of Cu-TCNQ subjected to an applied field shows a peak superimpos-able with the peak recorded for neutral TCNQ in Cs2(TCNQ" )3. 

A spontaneous electrochemical reaction is reported in magnesium-TCNQ salts. See Gutmann, F. Herman, A. M. Rembaum, A. J. Electrochem. Soc. 1967, 114, 323. 

The design of sensitive elements (transducers) is based on the conductive principle of response registration the output signal appears to depend on the conductive properties of the TCNQ compound as a result of its interaction with gas components. The gas-sensitive substance of the transducer has been manufactured from complex TCNQ salts with N-alkylisoquinoUnium cations ([N-C H -iso-Qn] (TCNQ)Q [26]. The substance of the gas sensitive layer is put in contact with copper or silver current feeding electrodes, put on the dielectric substrate manufactured from glass-cloth laminate. 

To obtain a gas sensitive continuum we used a special technique for sensor manufacturing, which allowed formation of a mesoscopic point-contact multistructure of TCNQ salts (Fig. 7.1). This structure is a set of a large number of resistant elements, namely point contacts [23], formed in the points of touching of the lateral... 

The effect of/on the conductivity of TCNQ salts can be visualized as follows for electrical conduction to occur, electrons must move from one TCNQ to another. When the charge transfer is complete, the process can be represented as... 

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