Rotations in Excited ICT States – Fluorescence and its Microenvironmental Sensitivity

Fluorescence spectroscopy as an analytical tool for various applications as well as fluorescence probes showing a sensitive behavior towards their microenvironmental properties have experienced an increasing interest in research in the last decades. Recently our group has contributed to this field of interest by introducing a novel mechanism where a planarization in the excited state occurs leading to an advantageous allowed emission. Here, we provide an overview of intramolecular charge transfer states where a rotation in the excited state causes a high sensitivity for microenvironmental changes. Furthermore, effects which influence the surroundings of the fluorophores are described in detail. Recent results where t wisted i ntramolecular c harge t ransfer (TICT) and a ggregation‐ i nduced e mission (AIE) effects were combined are described and a promising outlook for further research progress is provided.