6533b826fe1ef96bd12845ea

RESEARCH PRODUCT

Star-Shaped Push-Pull Compounds Having 1,3,5-Triazine Cores

subject

description

The 1,3,5-triazines 9–11 having OPV chains in the 2-, 4- and 6-position represent star-shaped compounds which exhibit strong push-pull effects. Their long-wavelength absorption S0 S1 is characterized by an intramolecular charge transfer (ICT) from the dialkylamino group as electron donor D via the conjugated chain to the 1,3,5-triazine core as electron acceptor A. Protonation of the dialkylamino group removes the donor capability, whereas protonation of the 1,3,5-triazine ring enhances the acceptor strength. Thus, the prevailing protonation site has a crucial influence on the push-pull effect and the ICT. The transition energies ΔE (S0 S1) pass through a minimum for the second generation 10 in the electroneutral series 9–11; on the contrary they pass through a maximum for 10b in the protonated series 9a, 10b, 11b. These unexpected results are explained by the superposition of different effects, namely the extension of the conjugation from 9 to 11, the decreasing ICT for growing distances of D and A, the aggregation, and the positions of the protonation in the presence of increasing amounts of CF3COOH. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)