Calix[6]arene acetic acid extraction behavior and specificity with respect to nucleobases

The extraction behavior of various nucleobases was investigated with a series of calixarene derivatives. A calix[6]arene acetic acid was found to extract around 80% of adenine from an aqueous phase, and showed the highest specificity for adenine among all the nucleobases tested. The important factors influencing the recognition properties of calixarene were discovered to be its cyclic structure, its cavity size, and the functional carboxylic acid groups. The carbonyl group and the position of the amino group in the guest molecules also affect the extraction efficiency. Calix[6]arene forms a stable 1:1 complex with adenine by entrapping it into the cavity. Adenine was readily recovered from the organic phase by contacting with a fresh acidic solution.