Pillar[5]arenes bearing phosphine oxide pendents as Hg2+ selective receptors

Pillar[5]arenes bearing ten phosphine oxide groups (1a–e), as analogs of their corresponding calix[4]arene-based phosphine oxide, have demonstrated intriguing recognition performance for some representative heavy metal cations including Co2+, Cu2+, Ni2+, Zn2+, Cd2+, Pb2+, Ag2+ and Hg2+ compared to their acyclic species (2a–e). Their extraction abilities toward these cations were evaluated by the solvent extraction method. The extraction results revealed that 1a–e were efficient and selective cation receptors for Hg2+ over other selected cations. In addition, the complexation behavior of 1a–e for Hg2+ was also investigated by using NMR and UV–vis techniques. The pillarareen receptors have been first used in the determination of inorganic mercury in natural water by inductively coupled plasma atomic emission spectrometry (ICP-AES), after back-extracting into aqueous phase with 3 mol L−1 HCl and 1% CS(NH2)2 solution.