A calixpyridinium–pyranine complex as a selective anion sensing assembly via the indicator displacement strategy

The recently reported calixpyridinium tetracation is shown to be very well-suited for anion sensing via the indicator displacement strategy. A very strong binding interaction between the positively charged receptor and the fluorescent pH indicator pyranine (8-hydroxy-1,3,6-pyrenetrisulfonate) requires an anionic guest of comparable negative charge for effective indicator displacement. Thus, selective and sensitive signalling of ATP is achieved in aqueous solutions.