Introduction Recently, many protable applications of photochromic dyes, particularly spirooxazines, either as passive or active devices, have been proposed [1-13].
In some cases, it has been reported that thermal equilibrium between the closed (colorless form) and opened form (colored merocyanine quinonoid form) is aected by the change in solvent polarity [14, 15], since polar solvents promote the formation of the colored form at room temperature in the absence of light. e equilibrium between both forms is strongly displaced upon irradiation to the side of open-chain colored photomerocyanine and spontaneously converts to the colorless spiro form to reach thermal equilibrium immediately after removing the light . e metal-ion coordination ability of photochromic spirocyclic compounds adequately substituted is of a great interest and is being the topic of several recent studies [12, 13]. Search for molecules possessing better performances is valuable and it is important to continue to explore this subject. Here, we report on the possibility to stabilize the colored open forms of the recently synthesized spirobenzoxazines SP(I) and SP(II) toward thermal bleaching by coordination with Tb3+ and Sm3+ ions in polar DMF solvent. Moreover, the expected light-energy transfer-induced characteristic luminescence of lanthanide ions via complexation with the merocyanine quinonoid open forms of the two spirobenzoxazines will be explored.