Unraveling the mechanism for fluorescent characteristics of probe 1 and DEASH

Abstract

In the previous experiment, probe 1, ((1E,1′E)-hydrazine-1,2-diylidenebis(methanylylidene))bis(5-(diethylamino)-2,1-phenylene) diacrylate, was synthesised to identify Cys. Probe 1 could process TICT by overcoming the potential barrier of 2.27 kcal/mol in the S1 state, resulting in the fluorescence quenching phenomenon. After combining with Cys, DEASH was generated. Not only did approximately 100 nm Stokes' shift occur in the S1 state, but other parameters, including primary hydrogen bond properties, infrared vibrational spectra, and interaction region indicator (IRI) further demonstrated ESIDPT process tended to occur in the S1 state. Although the potential energy surfaces in the S1 state evidenced that ESIDPT process could proceed by the stepwise pathway, the keto form wasn’t stable, preferring to remain in the enol form simply in the S1 state. In general, we illustrated the corresponding fluorescence quenching mechanism and specific ESIDPT process. It is promising that this work could be crucial in offering theoretical basis for similar molecular systems.