Ferrocenyl pyrazoline based multichannel receptors for a simple and highly selective recognition of Hg2+ and Cu2+ ions

We report here a simple one-pot synthesis, characterization and cation recognition properties of two benzothiazole based ferrocenyl pyrazoline derivatives (4 and 5). These compounds behave as highly selective multichannel sensors towards Hg2+ and Cu2+ ions in acetonitrile solution. An anodic shift of the ferrocene/ferrocenium couple, with a progressive perturbation in the lower energy band, was observed upon interaction of the cations with these receptors. A colour change, from yellow to brown and red, for Hg2+ and Cu2+ ions respectively enabled facile "naked eye" detection using the 'test strips' prepared from these receptors. The competitive metal-ion binding experiments indicated high selectivity towards Hg2+ as compared to Cu2+ ions. A 45-59 fold chelation enhancement of fluorescence (CHEF) towards Hg2+ ion was observed in the emission spectrum of 4 and 5. H-1 NMR studies and DFT calculations were used to determine the binding sites of receptor 4 involved in the complexation process. (C) 2014 Elsevier B. V. All rights reserved.