Tuning lipophilicity for optimizing the H2S sensing performance of coumarin–merocyanine derivatives.

Hydrogen sulfide (H2S) is an endogenous signaling molecule involved in various physiopathological processes; coumarin-based merocyanines have been successfully utilized for developing fluorescent H2S sensors. However, subtle changes in the chemical structure of merocyanines could induce distinct difference in the H2S sensing behavior. Investigation of the structure–property relationship of merocyanine dyes is of great importance for the development of ideal sensors with desirable performance. In this work, a series of coumarin/merocyanine (CMC) hybrid fluorescent probes with different lipophilicities have been developed. By altering the N-alkyl chain, the reaction rate with H2S and intracellular distribution of CMC sensors are optimized. The results showed that increasing the lipophilicity by attaching longer N-alkyl chains leads to a faster sensing response as well as a higher efficiency of the mitochondrial targeting ability. By virtue of rapid sensing of H2S and impressive mitochondrial co-localization ability, CM-NC6 could monitor H2S levels via a dual channel ratiometric mode. In addition, CM-NC6 is also capable of in vivo imaging of exogenous H2S. The work provided a powerful strategy for developing H2S sensors with optimized performance, which would be helpful for understanding the complicated roles of H2S in various physiological processes. [ABSTRACT FROM AUTHOR]