Electronic Transitions of Polyalkylthiophenes Partially Derivatized with NLO Chromophores: A Theoretical and Experimental Study

✍ Scribed by Massimiliano Lanzi; Franco Bertinelli; Luisa Paganin; Paolo Costa-Bizzarri; Gaia Cesari

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 166 KB
• Volume: 207
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200600192

✦ Synopsis

Abstract

Summary: The UV‐vis spectral profiles of some alkylthiophene copolymers in CHCl~3~ solutions, variously substituted with an azobenzenic NLO chromophore have been carefully analyzed and distinct intensity contributions have been assigned to the overlapped electronic transitions appearing in the lower energy part of the spectra. The different spectral behaviours are influenced by the chromophore content, the length of the alkylic side‐chain of the plastifying comonomer and, more significantly, by the number of the carbon atoms in the oligomethylenic spacer between the chromophoric group and the conjugated polythiophenic chain. This latter finding can be correlated with the strong steric hindrance caused by chromophore crowding in close proximity to the polymeric backbone. As the intensity distributions may be reasonably compared with the NLO properties, identification of the above parameters and of their role is an important step towards the synthesis of polyalkylthiophenes with predictable electronic properties and the development of materials with enhanced NLO characteristics.

Graphical surfaces of the highest‐occupied (HOMO)s and the lowest unoccupied (LUMO) molecular orbitals involved in the first three π–π* electronic transitions of the chromophoric system.

magnified imageGraphical surfaces of the highest‐occupied (HOMO)s and the lowest unoccupied (LUMO) molecular orbitals involved in the first three π–π* electronic transitions of the chromophoric system.