Synthesis of a New Thermal and Photostable Reference Probe for QfMeasurement in Aqua: Water Soluble N,N′-bis-(2-Hydroxy-4-benzoic Acid)-3,4,9,10-perylenebis(dicarboximide)

N,N′-bis(2-hydroxy-4-benzoic acid)-3,4,9,10-perylenebis(dicarboximide) is synthesized from perylene 3,4,9,10-tetracarboxylic dianhydride and 4-amino-3-hydroxy benzoic acid in 90% yield. Together with the photostability the dye is also very stable thermally. The fluorescence quantum yield is measured as one, Qf=1.The diimide dissolves in water at PH = 8 completely. The diimide is an ideal reference probe for fluorescence quantum yield measurements in 500–650 nm region and an attractive photosensitizer for the photoreactions occur in water.