Theoretical study the photophysical mechanism of fluorescent probe on detecting mitochondria-targeted hydrogen peroxide

The photophysical mechanism and dynamics behaviors of (E)-4-(2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)vinyl)-1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)pyridin-1-ium (Compound 1) on detecting hydrogen peroxide (H2O2) has been theoretically studied. The boron ester in Compound 1 is cleaved when H2O2 is added to the solution, resulting in the formation of (E)-7-(diethylamino)-3-(2-(pyridin-4-yl)vinyl)-2H-chromen-2-one (Compound 2). Theoretical calculations show that the fluorescence spectra of the compounds exhibit a significant blue shift from 616 nm of Compound 1 to 542 nm of Compound 2 before and after the reaction, which are in good agreement with the experimental results (640 nm -> 535 nm). The calculated electron-hole transfer distance of Compound 1 (5.986 & Aring;) is larger than that of Compound 2 (3.544 & Aring;), and Compound 1 is demonstrated to be charge transfer excitation while the Compound 2 is localized excitation, which results in a blue shift of the fluorescence spectra. The analysis of molecular electrostatic potential demonstrates that compound 1 has the highest electrostatic potential (4.60 eV) at the pyridine position and the lowest (-0.30 eV) at the oxygen atom of the coumarin moiety, suggesting that compound 1 undergoes fragmentation at this position. This study provides a theoretical explanation for the reaction mechanism of molecular probes.