The caged bulky dyes also display altered color and absorption properties, which remain intact even under acidic conditions. Furthermore, tetrasubstituted, bulky porphyrins are caught by the cage in aqueous solution. This peculiarity stems from the twist of the substituents in the cage, revealed by the combination of absorption and theoretical studies. The color of perylene bisimides with two bulky substituents is remarkably changed from yellow to red upon caging. The resultant caged dyes show unusual emission enhancement, depending on the difference of a single heteroatom in their substituents. Coumarins with two bulky substituents are bound by the cage in aqueous solution. In this report, on the other hand, three types of sterically demanding organic dyes trapped by a polyaromatic cage were investigated by spectroscopic analyses on the basis of supramolecular interactions. Host–guest structures and properties have been widely studied using relatively small dyes (<1 nm) without bulky groups, due to their smooth incorporation, efficient host–guest interactions, and high analytical accessibility.
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