Photophysical properties of the interaction of lower rim 1,3-bis(aminoethoxy)-calix[4]arene derivative with Pb<SUP>2+</SUP>, Hg<SUP>2+</SUP> and Cd<SUP>2+</SUP>ions: recognition of Hg<SUP>2+</SUP>

Interaction of heavy metal ions, viz., Pb2+, Hg2+ and Cd2+ with 1,3-bis(aminoethoxy)-calix[4]arene was studied using emission spectroscopy and the corresponding binding parameters were derived. Based on the changes observed in the fluorescence during titration with these metal ions, two types of species were proposed, viz., one in which the metal ion is bound at the lower rim, the other in which the metal ion interacts through the hydrophobic arene cavity. The extent to which these species were present depends upon the type of the metal ion as well as the number of metal ion equivalents added. The results were compared with unmodified calix[4]arene titration data. Based on these studies, Hg2+ can distinctly be recognized from the other heavy metal ions