Pillar[5]arenes bearing phosphine oxide pendents as Hg(2+) 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 Co(2+), Cu(2+), Ni(2+), Zn(2+), Cd(2+), Pb(2+), Ag(2+) and Hg(2+) 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 Hg(2+) over other selected cations. In addition, the complexation behavior of 1a-e for Hg(2+) 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.