CHROMOGENIC LIGANDS FOR LITHIUM BASED ON CALIX[4]ARENE TETRAESTERS BEARING NITROPHENOL RESIDUES

Three novel chromogenic calix[4]arene tetraesters bearing nitrophenol residues which dramatically change their UV-VIS absorbance spectra upo n complexation with metal ions have been investigated. Upon addition o f metal perchlorates such as lithium or sodium to a solution of the ca lixarene in tetrahydrofuran, in the presence of a base, a colour chang e from near colourless to yellow occurs. The colour density is depende nt on metal perchlorate concentration and can be monitored by UV-VIS s pectroscopy. All three compounds were found to be lithium selective wi th a 10-40 fold selectivity for lithium against sodium. No colour chan ge was noted in the absence of a base. From two-phase studies, it has been demonstrated that all three ligands have the ability to extract m etal ions from an aqueous phase into an immiscible organic phase (buta n-1-ol) which had been made basic by the addition of the lipophilic ba se triaodecylamine, with a colour change from near colourless to yello w occurring in the organic phase. The deprotonated calixarene metal io n complex was found to diffuse into the aqueous phase with time, with the rate of diffusion being strongly dependent on the lipophilic natur e of the calixarene backbone.