Sensing Mechanism of Excited‐State Intermolecular Hydrogen Bond for Phthalimide: Indispensable Role of Dimethyl Sulfoxide.

Main observation and conclusion: Excited‐state hydrogen bond strongly affects the intramolecular charge conversion process, which is very suitable for the design and development of high‐performance fluorescent probes. However, as one of the most common solvents or additives used in sensing, the role of dimethyl sulfoxide (DMSO) in the system of the excited‐state hydrogen bond is seldom explored. As the goal of this research, we investigated the sensing mechanism of a CORM3‐green fluorescent probe system for carbon monoxide releasing molecule (CORM‐3) detection and tracking in vivo, through quantum chemistry calculations based on density‐functional‐theory (DFT)/ time‐dependent density‐functional‐theory (TDDFT) methods. Based on the analysis of the solvent effect of DMSO by the reduced density gradient function and IR spectroscopy, we provided a new strategy to explain the fluorescence mechanism. Subsequently, we verified the result through the potential energy curve of Phthalimide (PTI, the reduced product of CORM3‐green). The excited‐state hydrogen bond between PTI and DMSO promotes radiation transition and leads to obvious difference in the photophysical properties of PTI and PTI‐DMSO. [ABSTRACT FROM AUTHOR]