Synthesis and evaluation of arylfuryl-bis(indolyl)methanes as selective chromogenic and fluorogenic ratiometric receptors for mercury ion in aqueous solution

A series of arylfuryl-bis(indolyl)methane derivatives were prepared in good yields by electrophilic substitution of indole with furyl aldehydes through a simple and mild hydrogensulfate-catalysed reaction and studied as chemosensors for transition metal cations by performing spectrophotometric and spectrofluorimetric titrations. Selective recognition of Hg2+ was achieved in organic aqueous mixture (CH3CN/H2O, 7:3) for the various receptors, with an easily detectable colour change from colourless to purple and also through a fluorescence quenching, making these compounds suitable for dual chromo- and fluorogenic ratiometric sensing of Hg2+. The binding stoichiometry between the receptors and Hg2+ was found to be 1:1. The binding process was also followed by H-1 NMR titrations which corroborated the previous findings. (C) 2013 Elsevier Ltd. All rights reserved.