Host-guest complexation studies of p-tertbutylcalix[4]arene against ions of interest for radiological decontamination

Cesium, strontium, cobalt, thallium and iodine are the most common radionuclides in Nuclear and Radiological emergencies. Calix[n]arenes are supramolecular compounds capable of forming complexes with most of the metal ions. In the current study, host-guest complex properties of p-tertbutylcalix[4]arene against the five ions have been studied using a combination of experiments and density function theory (DFT) calculations. Characterization of the formed complexes has been done by H-1 NMR, Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), circular dichroism (CD), UV-Vis. and fluorescence spectroscopy. Further, ex-vivo metal complexation studies have been performed using high-resolution sector field inductively coupled plasma mass spectroscopy (HR-SF-ICPMS). H-1 NMR host-guest complex studies provide spatial information about the location of the guest molecules in the host cavities. A detailed interpretation of the ATR-FTIR has been done in order to derive important information about the interaction mechanism of host-guest complexes. CD spectra of the complexes provide information about the conformational changes in the ligand structure. UV-Visible and fluorescence spectroscopy further validate the complexation of the metal ions with p-tertbutylcalix[4]arene. Detailed electronic structures of the complexes have been elucidated using computational methods involving DFT calculations and further verified using X-ray crystallography. More than 96% complexation of p-tertbutylcalbc[4]arene with the selected ions has been observed in ICP-MS. These studies confirm the utility of this supramolecular compound for topical radiological decontamination formulations.