Theoretical investigation and reconsideration of intramolecular proton-transfer-induced the twisted charge-transfer for the fluorescent sensor to detect the aluminum ion

Theoretical investigation on the sensing mechanism of a triphenylamine-benzofuran derived fluorescent probe for the detection of H2Sn

As one of the members of reactive sulfur species, hydrogen polysulfide (H2Sn, n > 1) plays an important role in enzyme activity and nervous system regulations, and the sensing mechanism study is of great significance for the design of novel efficient probes. Herein, we investigated the sensing mechanism of an efficient triphenylamine-benzofuran-based probe (TBF-SS) towards H2Sn using DFT method. The inherent fluorescence quenching of the probe is dominated by the twisted intramolecular charge transfer (TICT) as revealed by the torsional potential curve calculations. When the nitro fluorophenyl group is replaced by a hydroxyl group in the reaction with H2Sn, the TICT is eliminated and the excited state can return to the ground state in a radiative way, leading to strong fluorescence emission.