Investigation of para-sulfonatocalix[n]arenes [n = 6, 8] as potential chelates for (230)U.

Literature reports of the efficacy of para-sulfonatocalix[6]- and calix[8]-arenes as U(vi) complexants indicated that they might be useful for in vivo chelation of the novel therapeutic alpha-emitter (230)U. We have studied the complexation of U(vi) with para-sulfonatocalix[6]arene and para-sulfonatocalix[8]arene by time resolved laser induced fluorescence spectroscopy and using competition methods with Chelex resin and 4-(2-pyridylazo)resorcinol in simplified and in biological media. New thermodynamic parameters describing the stability of U(vi)-para-sulfonatocalix[n]arene [n = 6, 8] complexes were obtained. Although the interactions are strong, the complexes do not exhibit sufficient stability to compete with carbonate ions and serum proteins for complexation of U(vi) under physiological conditions.