Anthracene and Phenanthrene‐Based Barbituric and Thiobarbituric Acid Derivatives as Aggregation‐Induced Emission‐Enabled Wide Range of Water Sensors

To explore the aggregation‐induced emission properties (AIE), anthracene‐ and phenanthrene‐based derivatives of barbituric and thiobarbituric acid ( ABA , ATBA , PBA , and PTBA ) have been designed and synthesized with high yields. The anthracene derivatives of both barbituric and thiobarbituric acid ( ABA and ATBA ) show two absorption bands in their THF solutions; the lower energy band results from intramolecular charge transfer (ICT) from the donor, anthracene (A), to the acceptor, barbituric/thiobarbituric acid (BA/TBA), while the higher energy band corresponds to the π–π* transition of the anthracene unit. The phenanthrene derivatives of both BA and TBA exhibit only lower‐energy ICT bands. Generally, the ICT band of TBA derivatives red‐shifts compared to BA derivatives due to the stronger electron‐withdrawing nature of TBA. It is confirmed that the emission of all the compounds originates solely from their respective π–π* transitions and not from their ICT bands. When water is added to each of the THF solutions, PTBA exhibits aggregation‐induced blue‐shifted enhanced emission (AIBSEE), ATBA shows AIE, and both ABA and PBA display aggregation‐induced red‐shifted enhanced emission (AIRSEE). Notably, the AIBSEE of PTBA enables a wide range of water sensors.