Theoretical study on the sensing mechanism of ESIPT-based fluorescent probe for hydrogen sulfide detection derived...

Karakus et al. synthesized a turn-on fluorescence probe 3-(cyanooxy)-hydroxyflavone (FLVN-OCN) based on excited state intramolecular proton transfer (ESIPT) for detection of H₂S. However, both sensing mechanism of FLVN-OCN and ESIPT mechanism of sensing product (3-HF) remain poorly understood. Additionally, C=C bond was introduced to investigate the conjugated effects on sensing mechanism, ESIPT process and photophysical properties with time-dependent density functional theory (TD-DFT) method. The results found that (1) the fluorescence quenching of the probes was photoinduced electron transfer (PET) mechanism. (2) the introduction of C=C bond had little effect on the sensing mechanism of FLVN-OCN substituents. (3) the extent of ESIPT attenuation exhibited a positive correlation with the length of C=C bond chain. The theoretical findings provided a practical and guiding design strategy for the subsequent development of novel ESIPT-based fluorescent probes for H₂S detection.