AIDE – Design of aggregation-induced dually emissive bichromophores

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The aim of this project is the development of non-ionic bichromophoremitters with a dual emission or an environment-sensitive mixed color emission. Therefore, the diversity-oriented synthesis of novel bichromophore libraries is conceived and the systematic determination of molecular structural parameters of aggregation-induced dual emission (AIDE) of bichromophores constituted of diversely substituted merocyanines and triarylamines is studied by optical spectroscopy in solution, in particle systems and crystalline solids, assisted by quantum chemical modeling. Bichromophore emitters are envisioned showing environmental changes from aprotic vs protic or polar vs apolar by occurrence of mixed color emission that can be spectroscopically monitored.Two covalently bound emissive chromophores (donor: UV/vis-absorbing, blue emission; acceptor: red-shifted absorption, long wavelength emission) are placed within a Förster radius in a way that upon spectral overlap of the donor's emission band and the acceptor's absorp-tion band enables an energy transfer from „blue“ donor to „red“ acceptor. The red acceptor will be chosen such that its emission can be distinctly increased upon aggregation in solvent mixtures with variable polarity and/or proticity. The resulting emission color of these Bichromophore systems can be tuned by the efficiency of the energy transfer between donor and acceptor and by the efficiency of the acceptor's emission in dependence of its degree of aggregation. Therefore, partial energy transfer and aggregation-induced emission (AIE) of the acceptor are the prerequisites for the desired dual emission contributed by both donor and acceptor. The envisioned goals A) methodological development of the synthesis strategy for AIE-AIDE bichromophore systemsB) spectroscopic identification of merocyanine-based structures with particularly pronounced AIE properties of the acceptor and AIDE properties of the bichromophor system and the relevant molecular masses/environmental parameters such as polarity and viscosity and the temperature dependence of these influences; detailed investigations of the mechanism of the AIDE on selected bichromophores using spectroscopic methods such as time-resolved emission measurements (ps to ns range) and customer-based modelling (QM/MM treatment based on crystal structure analyses)C) mechanistic rationalization of the underlying energy transfer processesD) strategies for stabilization of bichromophore-based aggregates and preparation and characterization of water dispersible bichromophore nanoparticles E) aggregation studies on particle surfaces for prediction of the optical properties of markers on the basis of AIE-AIDE bichromophoreswill be achieved in synergetic collaboration between organic synthesis, physical organic chemistry and optical spectroscopy.