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Star‐Shaped Push‐Pull Compounds Having 1,3,5‐Triazine Cores
Author(s) -
Meier Herbert,
Karpuk Elena,
Christof Holst Hans
Publication year - 2006
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200600066
Subject(s) - protonation , chemistry , intramolecular force , triazine , photochemistry , conjugated system , ring (chemistry) , acceptor , electron donor , stereochemistry , polymer chemistry , organic chemistry , catalysis , polymer , ion , physics , condensed matter physics
Abstract 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 S 0 → S 1 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 Δ E (S 0 → S 1 ) 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 CF 3 COOH. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)