2-(Benzothiazol-2-yl)pyren-1-ol (P3-NS) was developed as a excited-state intramolecular proton transfer (ESIPT)- based sensor for nitroaromatic compounds (NACs). Results of studies of its photophysical and optical properties show that P3-NS exists in various, solvent dependent isomeric forms arising from rotation about the C–C bond connecting the benzothiazole and pyren-1-ol rings and the location of the pyrene-OH proton. The results of density functional theory (DFT) calculations enabled identification of the major structures of P3-NS dissolved in different solvents. Upon electronic excitation in nonpolar or weakly polar solvents, P3-NS undergoes an ESIPT reaction to form a product that only weakly fluoresces. In contrast, P3-NS exists in a strongly fluorescent deprotonated form in highly polar solvents. The results of time-dependent DFT calculations indicate that fluorescence quenching of the product generated by ESIPT reaction of P3-NS is caused by intersystem crossing at a conical intersection between S1 and T2 states. The anionic form of P3-NS, present in highly polar solvents, was shown to be a fluorescence sensor for nitroaromatic compounds (NACs). Fluorescence quenching by NACs occurs by protonation of the anionic form of P3-NS (static quenching) and by photoinduced electron transfer from the anionic form to NACs (dynamic quenching).
Bibliographical noteFunding Information:
S. P. is thankful for financial support from the National Research Foundation of Korea (NRF), which is funded by the Korea government (MSIP) (No. 2016R1A2B4011522 ). J.Y. is thankful for financial support from the National Research Foundation of Korea (NRF), which is funded by the Korea government (MSIP) (No. 2012R1A3A2048814 ).
© 2018 Elsevier B.V.
- Dynamic quenching
- Nitroaromatic compounds
- Static quenching