As shown in a, EM 1²⁺ can accept two electrons from H₂S, and converts into EM 2. The UV-Vis absorption of EM 1²⁺ is 

located above 500 nm, while upon reduction by H₂S, it is located below 500 nm. A distinct color change from blue to light yellow is obseved. This color change can be applied for the development of H₂S-activatable fluorescence imaging probes for in vivo imaging. We have published these results in 2018 (JACS, 2018, 140, 16340), with a great collaboration with Prof. Takanori Suzuki in Hokkodai Univeristy.