Synthesis of calix[4]arene-based polycarboxylate ligands and their chemical immobilization onto controlled-pore glass

Three new calix[4]arene-based carboxylate ligands with an appended allyl function have been synthesized, chemically immobilized onto a controlled-pore glass (CPG), and the extracting ability of selected materials towards Sr2+ in solid-liquid extraction was examined.
The calixarenes were characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopy, and where appropriate by X-ray crystallography. Four functionalized CPGs were prepared by radical thiol addition of the corresponding 5-allylcalix[4]arenes to γ-mercaptopropyl-modified CPG. Analysis by 13C and 29Si cross polarization/magic angle spinning (CP/MAS) NMR spectroscopy clearly showed the covalent fixation of the calix[4]arenes to CPG. The calix[4]arene phases were found to be stable up to 200° C by simultaneous thermal analysis (STA). The extraction performance of the modified CPGs towards Sr2+ were found to be superior over the unmodified CPGs as demonstrated by radiotracing using the short-lived radio nuclide 85Sr.