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|Type:||Artigo de periódico|
|Title:||Electronic structure of poly(tri-heterocycle) based on furan and thiophene: The role of the syn links|
|Abstract:||The electronic structures of poly(OSO) oligomers were theoretically analyzed. Models based on neutral and charged oligomers whose all rings (3<n<15) are linked to have syn or anti chains were considered. Geometrical optimizations were carried out at the semiempirical level using the parametric method 3 (PM3). The results indicated that the chain of the syn oligomer have a small curvature. For singly oxidized oligomers, the positive charge is concentrated around furan rings with a quinoid bond alternation pattern that extends at most six rings. For doubly oxidized oligomers, we also found a quinoid structure which extends up to eight rings. The energy of the electronic transitions and their associated oscillator strength values were also calculated for neutral and charged oligomers, so the UV-vis absorption spectra is presented. The calculations were done using the intermediate neglect of differential overlap Hamiltonian in combination with the single configuration-interaction technique in order to include correlations effects. The results indicated that the difference between the lowest unoccupied molecular orbital and highest occupied molecular orbital energies of the neutral oligomers are weakly correlated to the kind of their chains, although the different intensities of the lowest energy absorption peaks can be related to rings linked at the syn form. (C) 2002 American Institute of Physics.|
|Editor:||Amer Inst Physics|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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