Decoding Solvent Polarity Related Excited State Behaviors for the Novel Amino NH-type 3TfAPI Fluorophore

In this work, we mainly pay attention to solvent polarity dependent excited state behaviors for amino NH-type N-cyclohexylphthalimide-substituted trifluoroacetylamino (3TfAPI). Based on quantum chemical simulations, infrared (IR) vibrational spectra, atomic charge distributions, and photoinduced geometrical changes reveal hydrogen bond N-H center dot center dot center dot O should be enhanced in S-1. Particularly, enhancement effectiveness of hydrogen bonding with polar polarity solvent is more apparent. Exploring photoexcitation, we find photo-induced intramolecular charge transfer (ICT) plays critical roles in facilitating ESIPT tendency for 3TfAPI. By constructing potential energy curves (PEC5), we clarify detailed ESIPT mechanism for 3TfAPI, but also present solvent polarity regulated ESIPT behavior.