| Autor: |
Soungkyoo Kim, Annette Oehlhof, Bernhard Beile, Herbert Meier |
| Zdroj: |
Helvetica Chimica Acta; Jun2009, Vol. 92 Issue 6, p1023-1033, 11p |
| Abstrakt: |
Oligoparaphenylenes DAOPPs 2a–2dn=1–4 with terminal donor–acceptor substitution D=C6H13O, A=NO2 were prepared by applying Suzukicrosscouplings for chain extension and end capping. The push–pull effect induces shortreaching polarizations of the chain consisting of conjugated but twisted benzene rings, which was studied by NMR measurements. Electron excitation from the groundstate S0to the more planar firstexcited singlet state S1is combined with a strong intramolecular charge transfer ICT, which is documented by the red shift of the longwavelength absorption chargetransfer band for short chains one or two repeat units, n = 1 or 2. The opposite influence of decreasing ICT and increasing conjugation length leads to a bathochromic series λmaxn+1≥λmaxn with a fast saturation of λmaxn. The effective conjugation length nECL=4 corresponds to λ∞349nm. These results are discussed in the context of other oligoparaphenylenes OPPs. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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