Structure, dielectric relaxation and electrical conductivity of 2,3,7,8-Tetramethoxychalcogenanthrene-2,3-dichloro-5,6-dicyano-1,4-benzoquinone 1:1 charger-transfer complexes
| Autor: | Behrens, U., Díaz Calleja, Ricardo, Dötze, M., Franke, U., Gunsser, W., Klar, G., Kudnig, J., Oldrich, F., Sánchez Martínez, Enrique, Sanchis Sánchez, María Jesús, Zimmer, B. |
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| Jazyk: | angličtina |
| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia instname |
| Popis: | [EN] 2,3,7,8-Tetramethoxychalcogenanthrenes (5,10-chalcogena-cyclo-diveratrylenes, 'Vn(2)E(2)', E = S, Se) form isotypical 1:1 charge-transfer (CT) complexes with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). X-ray analysis of Vn(2)S(2) . DDQ shows the compound to have a columnar structure with segregated stacks of donors and acceptors. The donors are virtually planar in accordance with a formulation of [Vn(2)E(2)](+)[DDQ](-). Donor cations and acceptor anions are equidistant in their respective stacks, but in each case they inclined to the stacking axis, nevertheless guaranteeing an optimum overlap of the half-filled frontier orbitals which are of pi-type character according to MNDO calculations. Dielectric ac measurements of permittivity epsilon' and loss factor E '' clearly reveal two processes, a dielectric one at low temperatures and a conductive one at high temperatures. The dielectric process can be described by the Havriliak-Negami (HN) and the Kohlrausch-Williams-Watts (KWW) model, and the conductive process by a Debye-type plot. Using these methods, the relevant parameters are evaluated. The de conductivities of polycrystalline samples moulded at 10(8) Pa show a temperature dependence in the plots of ln sigma vs. T-1, which is typical of semiconductors. Two slopes are found; that in the low-temperature region ( |
| Databáze: | OpenAIRE |
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