Solvatochromic behavior, conducting

The electronic spectrum of (14) and its isomer (20) which both form highly conductive complexes with TCNQ and analogous acceptors have been reported <90BCJ244l>. The solvatochromic behavior of the ditellurides (1), (21), and (22) has also been discussed <93JA885>. 

In this chapter, the first section will deal with the complex question of conformations of polysilanes. This will be followed by sections on the chromotropism of polysilanes, beginning with their UV thermochromism. Despite intensive study this phenomenon is still not well understood, and is the subject of important recent findings. Solvatochromism, ionochromism and other types of chromotropic behavior of polysilanes will then be considered. A final brief section will deal with the electrical conductivity of polysilanes, a topic which has not previously been reviewed. 

Regioregular poly(3-alkylthiophene)s have received a lot of attention, especially because of their high electrical conductivities in the doped state, and because of their unusual solvatochromic and thermochromic behavior . Hence, a lot of research has been focused on clarifying the structure of these materials, both in the solid state and in solution. Today, it is agreed that supramolecular aggregation of polythiophene chains plays an important role in their physical properties. 

Preferential solvation has been studied in the light of various methods, most of which are based on conductance and transference measurements , NMR measurements of the chemical shift of a nucleus in the solute or measurements of the solvatochromism of a solute in the IR or UV-Vis spectral region. Plots of the data obtained from such measurements against the composition of the bulk solvent (usually as a mole fraction) depart clearly from the ideal behavior and the deviation is ascribed to the presence of preferential solvation. 

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