Binding of europium complex to polymerizable macrocyclic molecules and its optical properties

AbstractStudy on the incorporation of trivalent europium (Eu 3+ ) complex into polymerizable macrocylic molecules, namely calixarene andcalixresorcinarene derivatives, has been carried out. Broadening of hypersensitive luminescence peak was observed in solution and poly-mer containing a compound of europium complex and calixresorcinarene monomer, which is ascribed to ligand field splitting due toanisotropic local field at the Eu 3+ ion site. From 1 H NMR spectroscopy, it is found that the chemical shift originated from the moietyat the upper rim of calixresorcinarene is remarkably downfield shifted. Pseudocontact shift analysis suggests that binding between Eu 3+ ion and calixresorcinarene monomer is formed at the Eu 3+ second coordination sphere. These experimental results show that the bindingdoes not alter nephelauxetic effect of the Eu 3+ first coordination shell, but only slightly change coordination structure and symmetry.Nevertheless, the binding results in longer luminescence lifetime in comparison to the case of pure europium complex indicating signif-icant reduction of non-radiative decay. 2006 Elsevier B.V. All rights reserved.