Excited State Complexes of Coumarin Derivatives

Furocoumarins are the useful derivatives of coumarin, and they act as skin photosensitizing material due to their exciting exciplex states. Dendrimers also form exciplexes when they contain coumarin as core and used for light harvesting. A number of ingredients in human nutrition contain coumarins. The apiaceae family is the most common example of this class that contains carrots, celery and parsley etc. Rutaceae family is also an important food source that contains coumarins and provides citrus food. Besides fruits and vegetables, beverages like coffee, wine, black and green tea also incorporates coumarin derivatives. Few coumarin dyes show absorption and one emission peak but it can show a double amplified spontaneous emission band due to the generation of super exciplexes in coumarins. Exciplex formation of different coumarin derivatives including 7−methoxy coumarin, 7−hydroxy coumarin show wide application in synthesis of various other derivatives and they can be used as dye due to their prominent fluorescence properties. Exciplexes and excimers of coumarin are widely used in lasers. Both singlet and triplet state exciplexes are considered. Thus a comprehensive review of excited state complexes of coumarin derivatives is discussed here with emphases on the interaction and overlap of the energy levels.