Linear chain conducting systems

The electrical transport of KCP was reported by Zeller et The room-temperature conductivity along the molecular stacking direction is 300-400 S cm , which is 10 greater than the conductivity perpendicular to the chain direction. The temperature dependence of conductivity along the chain direction shows metallic behaviour down to around 250 K and semiconducting behaviour below that temperature. The broad maximum of conductivity around 250 K is due to the one-dimensionality of the linear-chain system. The large anisotropy of conductivity in directions parallel and perpendicular to the chains confirms the onedimensional character of KCP. 

The bis(oxalato)platinate(II) complexes based on [Pt(C204)2] , forms another family of linear chain systems, and the partially oxidised complex series, Cx[Pt(C204)2]-n(H20) (C = K, Rb, Mg " ", Co, Ni, Zn ), was reported.According to elemental analysis and X-ray diffuse scattering measurements, the formal oxidation state of platinum in this series is estimated in the range of -1-2.19 to -f2.38. The average Pt-Pt distance is 2.84-2.89 A and the conductivity at room temperature is 10 -10 S cm , depending on the associated cation. 

It is possible deliberately to incorporate more than one type of SRU into a polymer chain thus forming a co-polymer. An interesting example for linear ion-conducting polymers is the poly(ethylene/methylene oxide) system of Booth [21-23]. 

Borsini, et al.,f ] reported the use of a redox catalyst system for the polymerization of ethylene and chlorotrifluoroethylene. One advantage of this catalyst system was that it permitted operation at lower temperatures than with peroxides. It allowed production of polymers with a linear chain, an orderly distribution of the asymmetric points. This process had favorable economics due to the possibility of the recovery of the catalyst, followed by its oxidation and recycle. The catalytic system was comprised of an organometallic compound and tetravalent cerium salt in quantities ranging from 0.01 to 2 of the former and 0.001 to 1 of metallic cerium part by weight per hundred parts by weight of the monomer mixture. This catalyst allowed the polymerization reaction to be conducted in the range of -60 to 20°C. Examples of the catalytic system include Pb(C2H5)4 and (NH4)2Ce(N03)g. 

Conducting polymers have some similarities to conventional polymeric materials, but it is clearly the extensive main-chain tt conjugation and its implicit stiffness with respect to chain bending and twisting that most influences the overall physical behavior. As a direct consequence, virtually all linearly unsubstituted conducting polymers, as shown in Fig. 25.1 are found to be intractable and infusible. These model systems also tend to form crystalline phase structures with many common features. Hence these compounds may be con-... 

Ondrechen et al. have presented the results of model system calculations of discrete, bridged donor-acceptor complexes, and also of related linear-chain and two-dimensional network systems. These calculations have demonstrated how the bridging ligand can modulate the electron transfer and conductivity properties of the system. 

In the early stage of the development of molecular conductors based on metal complexes, partially oxidized tetracyanoplatinate salts (for example, KCP K2 [Pt(CN)4]Br0.30-3H2O) and related materials were intensively studied [6], In this system, the square-planar platinum complexes are stacked to form a linear Pt-atom chain. The conduction band originates from the overlap of 5dz2 orbitals of the central platinum atom and exhibits the one-dimensional character. 

In Chapter 7 I showed how much computational effort could be avoided in a system consisting of a chain of identical equations each coupled just to its neighboring equations. Such systems arise in linear diffusion and heat conduction problems. It is possible to save computational effort because the sleq array that describes the system of simultaneous linear algebraic equations that must be solved has elements different from zero on and immediately adjacent to the diagonal only. 

Figure 29. For the latter case, it is considered that the semiconducting re-electron systems are separated by insulating hydrocarbon spacers, resulting in alternate thin layers of organic semiconductor and insulator in these monolayer assemblies. The direct current - voltage (I - V) characteristics were mea- sured for the multilayers H2Pc(R)8 and Cu-Pc(R)8 in directions perpendicular and parallel to the film plane. In both cases, the linear I - V relationships of Ohm s law were observed at low electric field and obtained DC conductivities are summarized in Table 3. The normal conductivity (ajJ were ca. 10 13 S cm-1, while the lateral ones p//) were 3.4 x 10-7 and 9.9 x 10 7 S cm 1 for films of the metal-free and copper Pc derivatives, respectively. The former (ojJ tended to decrease slightly with increase of Figure 29. Schematical illustration of the substituent alkyl chain length,...

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