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.