The radical species being more emissive the fluorescence lifetime of both species 1c and 1c .-were determined. Average lifetime of 1c .-was found to be higher than that of 1c, indicating the prominent transition in the DHP unit in 1c .-compared to 1c (Figure , Table ). The emission intensity at 658 nm significantly decreased when a sample of 1c .-was exposed to 525 nm light, indicating the disappearance of the radical as the DHP ring opened (1c .-→1o) upon exposure to light (Figure ). Multiple cycles of the emission spectral changes were performed, showing no significant degradation of the sample (Figure ).