H2S is the third important signaling molecule in humans and its fluorescent probe-based detection is crucial in the diagnosis of many neuro diseases. The main purpose of the study is to propose a rational mechanism for the nucleophilic addition of H2S to coumarin indolenium (CouMC), which is a small molecule fluorescent probe for H2S detection. The carbons at a- and ?- sites of the quaternary ammonium nitrogen in CouMC are two probable reactive centers, denoted as 1,2- and 1,4- site respectively. The structures of CouMC, its derivatives and the addition products were optimized by density functional theory (DTF), which is a quantum mechanical computation method. Then the interaction between nucleophile (hydrogen sulfide anion) and probe molecules were studied by charge distribution. Upon comparison of the results, it is suggested that the 1,2- site is more electropositive than 1,4- site. Therefore, we believe the H2S addition is more likely to occur on the 1,2-carbon due to its more electronically favorable mechanism. The results will be further analyzed by natural bond orbital (NBO) theory.

Rational design of H<sub>2</sub>S fluorescent probes from quantum chemical calculations

248th National Meeting (2014)

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Rational design of H2S fluorescent probes from quantum chemical calculations

Rational design of H₂S fluorescent probes from quantum chemical calculations